The industrial expansion, population increase, and urbanization have generated numerous persistent organic contaminants (POCs) in the aquatic environment and affect the global clean water availability [1, 2]. Surfactants, medical waste, hazardous dyes, pesticides, fertilizers, and phenolic compounds for the leather, textile, cosmetics, paint, medicine, and plastics industries are among these contaminants. Due to their chemical toxicity, durability, cumulative nature, and bioaccumulation propensity, these contaminants pose a severe threat to aquatic ecosystems and human health, including cancer, hormone abnormalities, and embryotoxicity [3, 4]. Existing water treatment methods are in use, but have several serious challenges. Although slow, odoriferous, and inefficient against resistant chemical compounds, biological approaches work across strains [5]. Since other waste should be handled, membrane filtration and adsorption only transform contaminants [6, 7]. Reagents are needed for chemical flocculation and coagulation, which produce plenty of sludge [8]. Thermal oxidation can mineralize, but it is expensive and energy-intensive [9]. Traditional methods are highly resource-intensive and rarely mineralize complex organic contaminants [10]. Due to these limitations, non-conventional, energy-efficient, and green wastewater treatment technologies are required to mineralize hazardous contaminants completely, including the emerging organic contaminants (EOCs), before discharging them into waterways [11].

Advanced oxidation based on a photocatalytic approach is one of the most efficient and preferred techniques for degrading organic contaminants from wastewater in environmental and chemical engineering [12]. The advantages are simplicity, durability, relative inexpensiveness, complete degradation, and convenience of use. This environmentally safe, low-energy, renewable, and innocuous technology employs light energy to remove contaminants and accelerate operations for reducing contamination [13, 14]. Under standard atmospheric conditions, semiconductor photoactive materials completely mineralize contaminants into harmless end products such as CO₂, H₂O, and various minerals within this sustainable technology. These photocatalysts have a wide range of possible applications, including the production of H₂, the reduction of CO₂, antimicrobial effects, and N₂ fixation [15, 16]. Environmental applications, including wastewater treatment and air purification, can also utilize these photocatalysts. Researchers examined various semiconductors as highly effective photocatalytic materials for water treatment [17]. Well-known semiconductor photoactive materials included titanium dioxide (TiO₂) [18], cerium dioxide (CeO₂) [19], cobalt-aluminum layered double hydroxide (CoAl-LDH) [20], copper oxide (CuO) [21], strontium titanate (SrTiO₃) [22], graphitic carbon nitride (g-C₃N₄) [23], cadmium sulfide (CdS) [24], nickel oxide (NiO) [25], iron oxide (Fe₂O₃) [26], zinc oxide (ZnO) [27], and zinc sulfide (ZnS) [28]. Moreover, their advantageous electrical and optical characteristics, cost-efficiency, high surface area, lack of toxicity, chemical and thermal stability, eco-friendliness, recyclability, and high photostability and activity have sparked interest in contaminant photodegradation [29]. However, semiconductor photocatalysts, despite their widespread utilization, encounter several challenges. The challenges included in this context are (a) a low charge transfer rate, (b) an elevated rate of photocarrier recombination, (c) a large bandgap energy that constrains the absorption of visible light, and (d) limitations in scalability that limit the quality and effectiveness of material synthesis [30]. The overall performance of photocatalysis is influenced by multiple factors, such as the semiconductor material synthesis method, photoreactor configuration, and operating conditions, which strongly affect photocatalyst removal efficacy. Alternative methods to improve these materials’ intrinsic efficacy are widely researched. Doping to optimize carrier transport, surface modification and functionalization for photoactivity, morphology-based composite preparation for synergistic properties, bandgap engineering for light absorption, and heterojunctions for charge separation at interfaces are trending techniques [31, 32]. The photocatalytic activity of semiconductor-based catalysts can be improved. Photocatalytic materials utilize photon energy depending on the bandgap energy of catalysts and photoexcite electrons (e⁻) from the valence band (VB) to the conduction band (CB) [33]. Irradiating semiconductor photocatalyst materials with high-energy photons creates highly reactive reducing or oxidizing species, also known as reactive oxygen species (ROSs). Photocatalysis engages these ROSs with contaminants in chemical redox reactions [34]. Semiconductor photocatalysts mineralize inorganic and organic contaminants. Research on increasing the visible light absorption spectrum to employ the effective utilization of solar energy for industrial use and high quantum yield photoactivity is much needed. Modified advanced composite materials can facilitate the transition of laboratory-based photocatalytic mechanisms to industrial applications, thereby achieving these objectives [35].

Therefore, semiconductor photocatalysis developments should be critically assessed in light of the growing demand for practical applications and water treatment sustainability. This paper discusses potential semiconductor photocatalysts such as layered double hydroxide (LDH), piezoelectric photocatalysts, graphitic carbon nitride (g-C₃N₄), titanium dioxide (TiO₂), perovskite (ABO₃), zinc oxide (ZnO), and metal-organic framework (MOF). These materials are well-known systems and major examples of environmental light-driven catalysis research due to their attractive properties and targeted optimization. This analysis examines the complex structure-activity interactions that affect photocatalytic performance throughout various materials’ outcomes. In photocatalytic technology, innovative modification approaches improve optical, electrical, and structural features to overcome the above disadvantages and alter these semiconductor catalysts. This work covers semiconductor modification strategies like accurate bandgap tuning, systematic construction of complex heterojunctions, and surface plasmon-resonance (SPR) enhancement by decorating with noble metal nanoparticles, intentionally adding defects, and using co-catalysts and robust support materials. These methods aim to create advanced modified materials with lower surface redox reaction overpotentials, higher charge extraction kinetics, enhanced light harvesting, mechanical stability, and recyclability. This work integrates advanced modification methods with modern academic case studies on photocatalytic behavior to aid in mechanism and design rationale, as well as a bibliometric analysis that standard reviews lack. The paper compares semiconductor properties and discusses theoretical advances relevant to experiments and applications. This contribution covers fundamentals of photocatalysis, mass transfer mechanisms, reactive species generation, the 2007–2025 bibliometric background, and future research trends in the field. The study examines materials, methods, and interfacial engineering to improve charge dynamics, photostability, and visible light absorption in semiconductors to create robust, scalable, and environmentally friendly systems. The paper combines existing findings to suggest important future research avenues for hybrid and multi-mechanistic nanostructures that work in ambient solar light. Semiconductor photocatalysis is inevitable for circular and carbon-neutral wastewater treatment and preservation of the environment due to green synthesis, interface engineering, and sustainable, renewable energy-driven photoreactors.

The photocatalytic process has been extensively employed for the degradation of organic contaminants. This is primarily due to their ability to function at ambient pressure and temperature, as well as their capacity to completely mineralize pollutants and their byproduct materials without causing any additional harm [36]. Furthermore, these reactions are known for their low maintenance costs. Exposing the photocatalyst to light with an energy (E) equal to or greater than the bandgap energy (E_g) of the semiconductor catalyst materials initiates the photocatalytic process. The absorption of light energy excites electrons, causing them to shift from the VB to the CB [37].

This results in the formation of photoactive electrons (e⁻_CB) and holes (h⁺_VB). The adsorbed components are the ones that trigger the secondary chemical reactions with the photoexcited e e⁻_CB/h⁺_VB pairs [38]. The photoactivated e⁻_CB reacts when it comes in contact with O₂, and the h⁺_VB reacts with H₂O. The product of this process is highly reactive species such as superoxide radicals (O₂^•−), hydroperoxyl radicals (HOO^•), and hydroxyl radicals (•OH). The reactive species are critical in initiating the photodegradation of organic contamination [39, 40]. In order to achieve the best photodegradation efficiency, one should make sure that there is sufficient generation of these highly reactive species. The radicals are very reactive and can oxidize organic pollutants to produce water (H₂O) and carbon dioxide (CO₂) among other nonhazardous elements. It is noteworthy that this process does not result in any further contamination [41]. Excited e⁻_CB/ h⁺_VB pairs may recombine to release energy after the absorption of light. The active charge recombination is explained by the fact that the quantum efficiency of the semiconductor is low, and it affects its light-to-energy conversion capacity [42]. In the absence of recombination, the photoexcited e⁻_CB/ h⁺_VB pairs move to the catalyst surface, where they react with the adsorbed components [43]. Fig. 1(a) illustrates the mechanism of photocatalytic degradation of organic contaminants using semiconductor photocatalyst.

In a photocatalytic reaction, activated e⁻ transferred between the VB of a semiconductor photocatalyst to the CB upon exposure to light, leaving an equal number of photoinduced h⁺ in the VB. The light then excites some charge carriers, which move to the photocatalyst’s surface to participate in catalytic redox reactions [44]. Fig. 1(b) depicts the mass transfer process associated with the photocatalysis process. The mass transfer mobility and target pollutants in the conventional photo reactivity process can be categorized into four separate stages. During the initial stage, O₂ dissolves in the solution, while H₂O can adhere to the photocatalyst surface. These components react with photoexcited e⁻_CB/ h⁺_VB pairs to generate highly active radicals [45]. In the next stage, pollutants adsorb onto the surface of the catalyst and undergo chemical reactions with photogenerated species. During the third stage, final products and intermediates are produced by photocatalytic redox processes. The last stage removes photoexcited reactive redox species from the catalyst’s surface, forming final products (CO₂ and H₂O). Mass transfer from the bulk solution to the catalyst’s surface is crucial for high degradation performance [46]. Adsorption and desorption are affected by the amount of pollutants present, the temperature of the reaction medium, and the surface properties of the photocatalyst, such as its charge, area, and functional groups. Surface charge has an impact on electrostatic forces between pollutants and photocatalysts. A higher surface area improves the adsorption capability of active sites and eliminates pollutants. Mass transfer occurs when pollutants move from the bulk solution to the catalyst surface for adsorption and reaction [47, 48]. The photocatalyst adsorbed the reactants through the pore space for the redox reaction, and then desorption of the byproducts occurred to efficiently optimize the photoactivity. Photocatalytic material’s porous structure lets pollutants disperse [49]. Improper mixing, separation issues, pore shape, and the size of particles could prevent mass transfer. A concentration gradient can slow mass transfer and reaction if a lot of pollutants are near the catalyst surface. Mass transfer optimization can maintain reactant concentration at the catalyst surface, maximizing photocatalyst use and reaction rate [50].

In wastewater treatment research, the bibliometric study quantifies semiconductor photoactive catalysts that degrade contaminants. The figures and tables show the theme focus, publication volume, key journals, citations, and author influence. The pattern in question shows the progression of sustainable design, including traditional and innovative research. Fig. 2(a) shows how Scopus websearch identifies articles using fundamental data like publication year and field-relevant research reference details. The complete Scopus article selection method maintains dataset consistency and relevance. Scopus discovered 706 relevant articles after including the title, abstract, and keywords (semiconductor photocatalyst and wastewater treatment). Materials science, chemical engineering, and environmental science refine important articles. Because the data comes from a rigorously selected and thematically appropriate database result set, this selection process helps reduce extraneous data and ensures that the bibliometric analysis is more reliable. The annual output of literature data illustrates the exponential growth in scientific research on semiconductor photocatalysis in Fig. 2(b). The issue was covered in a single article that was published in 2007, but by the year 2015, there were a total of eleven papers that were accessible through online databases. The number of articles significantly increased from 20 to 75 between the years 2017 and 2021. In addition, the data reveal that there has been a constant upward publication trend during the years that have passed between these two locations. The exponential growth of semiconductor photoactive catalysts shows that more and more academics and researchers are interested in them. Minor fluctuations punctuate the upward trend, demonstrating original ideas’ persistence and importance. Until a more effective method for material development and wastewater treatment emerges, this reasoning remains valid. The Sankey diagram in Fig. 2(c) shows the complex relationship between notable authors, frequently cited publications, and key terms in semiconductor photocatalysis. The 1972 research by Fujishima and Honda remains influential, while newer scholars like Amit Senthil and Kumar have strong search and citation rates. The authors of the articles examine various methodologies and materials modifications, such as heterojunctions, improved semiconductors, wastewater treatment, and photocatalysis. This map shows the collaborative database and how foundational research affects recent author contributions on TiO₂-based systems and organic contaminant degradation. This map shows the field’s conceptual history and challenges.

Table S1 summarizes the dynamic development that semiconductor photocatalysis research has influenced. Annual publications (N) increased exponentially from 2007 to 2025, indicating strong field growth. Over this span, the mean total citation per item drops from early heights (1400 in 2008) to later lows (28.31 in 2024). In fast-expanding fields, the average citation per article decreases as the output multiplies, especially for recently published articles with limited citation years. Due to restricted time for citation accumulation, the mean total citation per year has decreased in recent years. This data shows the field’s rapid growth and requires age-normalized criteria for effect assessment.

Fig. 3(a) demonstrates that the Journal of Hazardous Materials, Environmental Science and Pollution Research, and Applied Catalysis B: Environmental are the most important publishing sources for high-impact research in this field. Journals like Environmental Science and Pollution Research have notable cumulative developments in article publishing. Table S2 displays the most widely cited research on semiconductor photoactive catalysis. Foundational contributions in material science and detailed overviews are shown in the table from Advanced Materials and Chemical Society Reviews. Early advances in visible-light-active TiO₂ and heterojunction photocatalysts were made by Wang (2014) and Low (2017) in Chemical Society Reviews and Advanced Materials, respectively. The regular publication of the Journal of Hazardous Materials and Applied Catalysis B: Environmental (e.g., Akpan, 2009; Peláez, 2012) highlights their importance in publishing practical research on organic contaminant degradation. Several highly cited studies (Gaya, 2008; Li, 2016; Ong, 2018) focus on review articles, showing a need for comprehensive syntheses of developments in ZnO, TiO₂, and g-C₃N₄-based photocatalysts. It indicates that innovative research regarding catalyst growth and analytical review studies shape the discipline. Fig. 3(b) illustrates the production of review articles by publishing sources over time, highlighting a steep increase in the top five sources after 2018 and a significant rise from 2020 to 2025. The rapid increase shows semiconductor photocatalysis’ growing environmental importance and intellectual interest. The increase in journals shows a significant increase in research output. Fig. 3(c) recognizes R. Asahi and P. Sharma as prominent and notable researchers in the field. These writers’ large number of published articles and dispersed research investigations suggests a strong interest in subdisciplines beyond photocatalysis, placing them to lead research in these areas. Understanding these influential authors can help define potential collaborations and research pathways. Fig. 3(d) demonstrates the keyword cloud, which includes photocatalysis, photocatalytic activity, semiconductor, TiO₂, and water/wastewater treatment. These phrases emphasize application-oriented and material development research in the literature. The addition of degradation and organic contaminants emphasizes photocatalysts’ practical significance, which matches the proposed semiconductor photocatalyst study. The absence of sophisticated alteration techniques in the keywords may allow the review to synthesize upcoming strategies that are not yet central to the keyword landscape.

The advanced oxidation process (AOP) effectively photodegrades hazardous organic contaminants in industrial wastewater, offering easy handling, notable reproducibility, simple operations, and high efficiency [51]. Under standard operational conditions, the technique employs atmospheric oxygen to completely mineralize organic contaminants into benign byproducts, utilizing a relatively inexpensive and effective strategy [52, 53]. This process is recognized as an ecologically sustainable, non-toxic, and low-energy consumption method for the decomposition of toxic substances. Light energy irradiation alone does not solely achieve the photoreaction process; photocatalysts, a critical component of the technique, harness photon energy to initiate redox reactions in a suitable reactor system [42]. The primary challenges in employing semiconductor photocatalysts, according to numerous studies, are [54, 55]:

Consequently, various teams of researchers are investigating methods to address the limitations in visible light absorption utilized for solar-powered photoexcitation. These strategies are designed to produce certain results, such as using cation or anion doping to speed up the photocatalytic reaction and adding more conductors and semiconductor photocatalysts [56]. Alternative approaches, including vesicles, microemulsions, and micelles, have been documented to mitigate active carrier recombination [57]. The mechanism of photocatalytic chemical reactions, as outlined in Eqs. (1–20), can be summarized as follows [58]:

Photoinduced e⁻ release energy as light or heat through recombination and revert to their original state in the VB where they were photoexcited [59]. Photocatalysts with a narrow bandgap experience a greater recombination disadvantage than those with a wide bandgap. Catalysts with a large bandgap typically employ ultraviolet (UV) light to enhance their performance. The primary focus in this research area for water treatment is to synthesize a competitive photocatalyst to address its reported limitations [52].

Single semiconductor photocatalysts, while offering various advantages, exhibit several limitations, including high charge recombination, restricted light absorption, inadequate charge carrier mobility, a broad bandgap, limited active sites, and low durability during extended operation. Several strategies are implemented to increase the efficiency of semiconductor photocatalysts in degrading toxic contaminants by addressing the material-related limitations. These strategies include defect engineering, bandgap modification, heterojunction formation, dye sensitization, morphological engineering, doping (with metal and non-metal elements), generating oxygen vacancies, substrate immobilization, addition of co-catalysts, integration of quantum dots, plasmonic enhancement, photo-electrocatalysis (bias-assisted), and surface alteration. The modifying strategies mentioned above can achieve high charge transfer and separation rates, reduced bandgap, increased reactive species production, better mass transfer efficiency, enhanced catalyst electronic properties, increased active sites, photoactivity under visible light irradiation, improved photo-redox reaction rates, boosted material conductivity, better e⁻/h⁺ pair generation, low recombination rates, and upgraded surface and physical properties. The following section discusses and investigates some extremely efficient techniques that improve the degrading characteristics of semiconductor photocatalysts, along with relevant published case studies.

Global environmental challenges are driving semiconductor photocatalysis’ efficacy, sustainability, and functional diversity. The photocatalysis field is growing, but its future depends on addressing multiple interconnected challenges [307]. Developing visible light-driven photocatalysts is essential because 40–48% of the natural solar spectrum is visible and abundant. This spectrum must be effectively utilized by photoactive materials to gather solar energy [308]. Persulfate-based systems, doping, heterojunction formation, and bandgap tuning strategies are being utilized to optimize occupant light harvesting and charge carrier behavior, but their structural durability and sustainable working under harsh conditions remain major obstacles [309]. The diametrical fabrication of single atoms and defect-abundant catalysts would regulate surface active sites microscopically for improved charge transfer and photoredox efficiency. They enable nearly complete atom and photon-to-electron conversion, aligning photocatalytic innovation with green chemistry and energy savings [310]. These discoveries in machine learning and AI have altered catalyst development by predicting synthesis conditions and appropriate formulations. System-level AI trained on big, high-quality databases can reduce empirical testing, accelerating innovation and reducing investment costs [311]. The circular economy revolutionized photocatalytic research. Waste organic matter from agriculture or industrial residues might enhance catalyst performance and reduce waste for large-scale applications [312]. Engineering issues, including photocatalytic reactor design and catalyst recovery & disposal, must be addressed to achieve these economic and environmental benefits [313, 314]. Nanoparticle aggregation and low recovery in typical slurry photoreactors increase process expenditures, waste, and secondary contamination. Immobilized catalytic material systems enable post-reaction modification; however, their limited active surface area impairs kinetics [315, 316]. Mass transfer restrictions and light distribution make large photocatalytic reactor systems ineffective at decomposing contaminants. Photoreactor concepts, material recovery mechanisms, continuous optical engineering, and safety procedures for disposing of catalytic materials after treatment must be addressed to maintain reaction efficiency and photon flux over long operation [317, 318].

Semiconductor-based photocatalysis must scale sustainably and functionally. Research on advanced semiconductor photocatalysis requires a fundamental transition from the real world, unattainable by incremental efficiency increases. Photocatalysis, persulfate-based AOPs, and membrane technology have transformed contaminant-degradation systems [319]. Photocatalysis and persulfate-based AOPs have revolutionized the decomposition of persistent organic contaminants that conventional oxidation cannot eliminate. A dual photo-oxidation system with redox potentials above 2.6 V was formed by semiconductor photocatalysts activating persulfate (S₂O₈^2-) to generate sulfate (SO₄•⁻) and ROSs [320]. Under visible light, hybrid systems remove 95% of harmful pharmaceuticals, dyes, phenolics, and hazardous emerging chemical toxins. To be efficient, these methods must maximize ROS generation kinetics and reduce parasite radical scavenging in complicated water matrices [309]. Next, rational bandgap tuning, defect engineering, and surface functionalization of photoactive materials can enhance persulfate activation under solar light irradiation, along with quantitative radical dynamics modeling to improve reaction selectivity and reduce secondary byproduct formation [321].

Hybrid photocatalytic membrane reactors (HPMR) are another advancing technology that is trending for practical application use. HPMRs are effectively capable of eliminating contaminants and immobilizing the active photocatalyst throughout a single operational analysis, while slurry methods fail to recover material and leach nanoparticles [322, 323]. This method uses fouling and physicochemically resistant substrates with photocatalysts for continuous flow oxidation. Recent investigations suggest that modifying the membrane surface chemistry and pore architecture can increase permeate flux and rejection efficiency by 90–95%, while reducing energy demand and pressure drops [324]. Photocatalyst immobilization sometimes causes partial inactivity/deactivation due to interfacial recombination losses or light-shielding consequences, requiring photocatalyst and membrane interfacial engineering modification [325]. Prospective studies must produce systematically configured membranes with strategically scattered catalysts to ensure uniform and maximum active site exposure, improved charge transfer kinetics for long-term photoactivity, and adaptive wettability characteristics for improved efficiency [326]. Wang et al. (2017) examined the degradation of ofloxacin (OFLX) using a persulfate-based inorganic-organic composite incorporated into a polyvinylidene fluoride (PVDF) membrane, subjected to ultraviolet (UV) light in a membrane chemical reactor (MCR), showing a substantial advancement in the field. The composite membrane Na₂S₂O₈@PVDF-g-PDMAEMA/PVDF combines persulfate-based AOP with separation by membrane for the treatment of wastewater. The membrane combines SO₄•⁻ production with PVDF ultrafiltration, synthesized using non-solvent induced phase inversion separation, sequential atom transfer radical polymerization, and following dipping treatment. The system removed 54% OFLX in 30 min, surpassing single-process controls of 7% and 13.7%, respectively. Persulfate generates SO₄•⁻ (E° = 2.5–3.1 V) via in situ UV activation and electrostatic attraction of S₂O₈^2- anions through positively charged N,N-dimethylaminoethyl methacrylate (PDMAEMA) substitutes, resulting in improved oxidation efficiency. Uniform distribution of Na₂S₂O₈ and PDMAEMA integration was established using structural characterization, enabling radical production and contamination absorption. Operational stability was observed as a drawback; after reuse (10 cycles), OFLX elimination dropped 40% (from 54% to 14%), comparable to UV alone functioning. Efficiency declines with Na₂S₂O₈ depletion, which points to the importance of reversible activation through electrochemical recovery. In real wastewater treatment applications, persulfate-integrated multifunctional membranes have both performance potential and endurance constraints. This work evaluates the synergistic increase of membrane filtration and photocatalytic oxidation [327].

Used photocatalysts should be properly managed following functional depletion or degradation to ensure economic and environmental viability. Final safe disposal and selective preservation through regeneration are the primary traditional options, depending on photocatalyst composition, functional restoration possibilities, and residual harmful effects [328]. Effective disposal needs extensive precautionary measures to prevent secondary contamination and hazardous species leaching from metallic catalysts (e.g., CdS, Cu₂O, PbS, Sb₂S₃, and particular MOFs). To immobilize chemicals and limit leachability, previous stabilization, commonly with cement encapsulation, makes landfilling environmentally acceptable [329]. Incineration, however rare for robust inorganic semiconductors, adds Valorization strategies focus on resource recovery and functional rehabilitation, recovering noble metals (e.g., Ag, Pt, Ir, Pd, Au/TiO₂) and reprocessing semiconductor oxides (e.g., SrTiO₃, TiO₂, ZnO, WO₃, Cu₂O) while preserving structural integrity [330, 331]. Prolonged photocatalyst lifespan is achieved through thermal treatments to minimize organic fouling, targeted surface reactivation, and chemical washes to eliminate surface poisons. If they are physicochemically stable, fully deactivated materials can serve as inert fillers or adsorbents [332]. Innovative catalysts exhibiting intrinsic recyclable properties, such as durable composites, core-shell architectures, and magnetically separable components, are under development; however, large-scale water treatment uses encounter challenges related to scalability and cost competitiveness [314].

Future semiconductor photocatalysts depend on AI guidance, atomically customized materials, visible light responsiveness, and a hybrid system-scale. Advances in persulfate-assisted photocatalysis, hybrid reactors, and membrane-integrated systems can influence wastewater treatment with solar photocatalysis. Photocatalytic materials that balance efficiency, long-term stability, and operation cost can be more commercially viable. Modular, consistent systems can assure acceptable degradation efficiencies during continuous operation, eliminating practical concerns and enabling semiconductor photocatalysis from lab discovery to scaled-up environmental remediation systems. Materials science, process technology, and computational engineering must be combined in innovative hybrid systems to scale large-scale photocatalysis from a promising laboratory approach to an environmentally viable remediation technology.

Semiconductor materials have made great strides in degrading hazardous organic contaminants in wastewater, giving an attractive and effective alternative to traditional methods of treatment that typically underperform. Materials like LDHs, TiO₂, g-C₃N₄, perovskites, ZnO, and MOFs are at the forefront of photocatalytic research due to their ability to use UV or visible light, large surface area, physicochemical stability, and ecological suitability. The significant interlayer anion transfer capacity and structural flexibility make piezoelectric materials and LDH-based photocatalysts promising for contaminant absorption and degradation. Pristine semiconductor materials, despite their advantageous properties, face limitations such as rapid charge recombination, wide band-gaps, restricted absorption of visible light, insulating characteristics, and instability in aqueous environments. Advanced strategies are essential for addressing these inherent deficiencies and improving photocatalytic efficacy. To overcome these constraints, heterojunction fabrication, bandgap adjustment, and ion doping have been suggested. Type-II and Z-scheme heterojunctions improve light absorption and photoactive carrier lifespan. Although piezoelectric semiconductor catalysts improve photoactive carriers’ mobility under mechanical stress, they are intriguing possibilities, but most reported systems need high-frequency ultrasonic vibration, which uses energy. Development of piezocatalysts that optimize the particle size and surface-active sites, respond well to low-frequency mechanical forces, and have piezoelectric coefficients to maximize degradation efficiency with little energy input should be the future step. The bibliometric analysis of semiconductor photocatalysts from 2007 to 2025 identifies prominent authors and their affiliations, key terms, trending topics, citation metrics, publication frequency, and relevant journals in the field. The bibliometric study reveals a significant increase in scholarly and research engagement with semiconductor photoactive catalysts.

Semiconductor photocatalysts have applications beyond water treatment, including CO₂ reduction, clean air, H₂ generation, and natural and renewable energy activities. However, difficult manufacturing procedures, high synthesis expenses, and real environmental system performance discrepancies limit their large-scale application. Scalable and inexpensive synthesis methods with long-term stability under practical operational circumstances are required to overcome these obstacles. Future photocatalytic performance improvements will require targeted semiconductor material modifications. Defect engineering can improve active sites and carrier mobility by adding lattice deformities or oxygen vacancies. Bandgap engineering optimizes solar energy by tailoring light absorption to the visible range. Developing heterojunctions, especially type-II and Z-scheme systems, improves charge transfer and separation, whereas noble metals increase light harvesting and electron (e⁻) excitation through surface plasmon resonance (SPR). We discussed numerous current academic articles as case studies to demonstrate the practicality of these property enhancement techniques. In wastewater treatment, heterojunctions, defect and bandgap engineering, and surface plasmon resonance (SPR) have been performed effectively. Data-driven optimization, materials design, and hybrid photoreactor technology are all required to move semiconductor photocatalysis from lab to industrial water treatment. Reproducible degradation efficiencies of >90% under visible-light circumstances in continuous-circulating photoreactors must be quantified. If the long-term stability of the photocatalyst and the efficiency of charge transfer are measured, integrated persulfate-assisted and membrane-coupled hybrid photocatalytic reactors can reach this goal. Closed-loop recovery and regeneration frameworks ensure catalyst utilization efficiency exceeds single-use models by limiting additional waste. Semiconductor photocatalysis becomes essential to the sustainable restoration of the environment because it requires scalable, modular structures that can support high reaction efficiency with low energy costs. Combining these methods allows for the design of highly stable, active, and economically feasible catalysts that promote long-term restoration of the environment.