Research progress in metal sulfides for photocatalysis: From activity to stability

Construction of direct Z-scheme Co9S8/CdS with tubular heterostructure through the simultaneous immobilization and in-situ reduction strategy for enhanced photocatalytic Cr(VI) reduction under visible light

Tubular Co9S8/CdS heterostructures have been successfully synthesized by in-situ growing CdS onto Co9S8 nanotubes through a simultaneous immobilization and in-situ reduction strategy. It turned out that the so-obtained heterostructure with Co9S8/CdS molar ratio of 1/10 can display a broad light absorption edge and especially much enhanced capacity for photocatalytic reduction of Cr(VI) under visible light. The characterization analysis and experimental results suggested that an interfacial electrostatic field between Co9S8 and CdS elements in the heterostructure could be constructed due to their different Fermi levels, allowing for more quantities of highly reductive electrons to participate in the photocatalytic reaction. Therefore, the so-obtained Co9S8/CdS (1/10) heterostructures could achieve the photocatalytic reduction efficiency of 100% within 20 min, which was more than two and four times larger than that of pristine CdS and Co9S8, respectively. Moreover, the possible photocatalytic reaction mechanism for reducing Cr(VI) was investigated and found to follow the direct Z-scheme charge transfer pathway. This novel fabrication route for composite photocatalysts with tubular heterostructures could lead to the widespread implementations for the elimination of various harmful pollutants in the process of environmental governance.

Highly efficient photocatalyst fabricated from the recycling of heavy metal ions in wastewater for dye degradation

Water pollution and energy crisis are becoming global and strategic issues that people are closely concerned about. Green and energy-saving photocatalytic technology is developing rapidly in solving global energy crises and environmental pollution problems. Therefore, we propose the "kill two birds with one stone" strategy to design efficient photocatalysts for dye wastewater treatment by utilizing heavy metal ions in wastewater. The adsorption properties of Mordenite (MOR) were utilized to removal heavy metal ions (Cd2+ and Zn2+) from waste water, and the adsorbed heavy metal ions were dried and sulfurized to obtain CdS/ZnS/MOR(ZnCdM). Then, g-C3N4 was ultrasonically dispersed and composited with ZnCdM by self-assembly, 25 wt% ZnCdCM photocatalytic material was obtained with a degradation rate of 99.8% in 1.5 h for Rhodamine B(RhB). It was found that MOR can provid adequate support for active substances, and the surface of MOR with smaller sizes of CdS nanoparticles, ZnS nanoparticles and g-C3N4 nanosheets, which increased the specific surface area of the materials and improved the reactivity. The porous structure of MOR is favorable for the enrichment of RhB, and the electric field effect of MOR leads to the decrease of the photogenerated carrier complex rate in the semiconductor, which increases the catalytic efficiency. In addition, the double Z charge transfer mechanism formed by CdS, ZnS, g-C3N4 is favorable for separating photogenerated carriers. These synergistic effects improved the photocatalytic efficiency. This strategy will be a green and promising solution to water pollution and energy crisis.

Atomic/molecular layer deposition strategies for enhanced CO2 capture, utilisation and storage materials

Elevated levels of carbon dioxide (CO2) in the atmosphere and the diminishing reserves of fossil fuels have raised profound concerns regarding the resulting consequences of global climate change and the future supply of energy. Hence, the reduction and transformation of CO2 not only mitigates environmental pollution but also generates value-added chemicals, providing a dual remedy to address both energy and environmental challenges. Despite notable advancements, the low conversion efficiency of CO2 remains a major obstacle, largely attributed to its inert chemical nature. It is imperative to engineer catalysts/materials that exhibit high conversion efficiency, selectivity, and stability for CO2 transformation. With unparalleled precision at the atomic level, atomic layer deposition (ALD) and molecular layer deposition (MLD) methods utilize various strategies, including ultrathin modification, overcoating, interlayer coating, area-selective deposition, template-assisted deposition, and sacrificial-layer-assisted deposition, to synthesize numerous novel metal-based materials with diverse structures. These materials, functioning as active materials, passive materials or modifiers, have contributed to the enhancement of catalytic activity, selectivity, and stability, effectively addressing the challenges linked to CO2 transformation. Herein, this review focuses on ALD and MLD's role in fabricating materials for electro-, photo-, photoelectro-, and thermal catalytic CO2 reduction, CO2 capture and separation, and electrochemical CO2 sensing. Significant emphasis is dedicated to the ALD and MLD designed materials, their crucial role in enhancing performance, and exploring the relationship between their structures and catalytic activities for CO2 transformation. Finally, this comprehensive review presents the summary, challenges and prospects for ALD and MLD-designed materials for CO2 transformation.

Efficient degradation of sulfonamides by introducing sulfur to magnetic Prussian blue analog in photo-assisted persulfate oxidation system

The peroxynitrite photocatalytic degradation system was considered a green, convenient, and efficient water treatment process, but not satisfying against some antibiotics, e.g. sulfonamides (SAs). To improve the photocatalytic degradation efficiency of SAs, sulfur was introduced to a magnetic Fe-MOF (Fe-metal organic framework) Prussian blue analog to achieve a heteroatomic material CuFeO@S, which was applied in heterogeneous visible light photo-assisted catalytic process with persulfate (PS) as an oxidant. The characterization results of CuFeO@S by XRD and XPS confirmed the presence of Fe3O4 (for magnetic separation), Cu+ (for activation of PS) and S2- (for narrowing the energy band and prolonging the lifetime of photo-generated electronics). Through systematic optimization of reaction conditions in CuFeO@S + PS + hv system, efficient degradation of four tested SAs was achieved in 30 min (removal rate of 97-100% for the tested 4 SAs). Moreover, the material could be magnetically recycled and reused for over 7 cycles with a removal rate of >90% for sulfamerazine. Furthermore, the removal rate of sulfamerazine in pond water reached 99% at a mineralization rate of about 34% (decrease in total organic matter), demonstrating its potential in the treatment of antibiotic-containing wastewater.

Rational design of CdS-enwrapped polypyrrole nanoparticles for wastewater treatment: removal of hazardous pollutants in aqueous solutions

The modern world requires a chemical industry that can run at low production costs while producing high-quality products with minimal environmental impact. The development of environmentally friendly, cost-effective, and efficient wastewater treatment materials remains a major problem for the sustainable approach. We prepared nanoscale cadmium sulfide (CdS)-enwrapped polypyrrole (PPy) polymer composites for degradation of organic pollutants. The prepared CdS@PPy nanocomposites were characterized by powder X-ray diffraction, scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible (UV) absorption spectroscopy, indicating proper intercalation between CdS and PPy. Consequently, the catalytic efficiency of the synthesized hybrid nanocomposites was analyzed through the degradation of methylene blue (MB) and rhodamine B (Rh B) under visible light irradiation. The measured degradation efficiency of the dye solutions under the photolysis process is about 18% and 23% for MB and Rh B dye, respectively. Furthermore, the recycle test result concludes that the CdS@PPy composite exhibits 91% and 89% of MB and Rh B dye degradation efficiency even at the 4th cycle, respectively. The positive synergistic impact of CdS and PPy may be the result of effective photocatalytic degradation of MB and RhB.

Polyarene Oxides with Tunable Quinone Units for Photocatalytic CO2 Reduction: A Simple Strategy toward Effective and Selective Catalysts

The photocatalytic transformation of carbon dioxide (CO2) into valuable chemicals is a challenging process that requires effective and selective catalysts. However, most polymer-based photocatalysts with electron donor-acceptor (D-A) structures are synthesized with a fixed D-A ratio by using expensive monomers. Herein, we report a simple strategy to prepare polyarene oxides (PAOs) with quinone structural units via oxidation treatment of polyarene (PA). The resultant PAOs show tunable D-A structures and electronic band positions depending on the degree of oxidation, which can catalyze the photoreduction of CO2 with water under visible light irradiation, generating CO as the sole carbonaceous product without H2 generation. Especially, the PAO with an oxygen content of 17.6% afforded the highest CO production rate of 161.9 μmol g-1 h-1. It is verified that the redox transformation between quinone and phenolic hydroxyl in PAOs achieves CO2 photoreduction coupled with water oxidation. This study provides a facile way to access conjugated polymers with a tunable D-A structure and demonstrates that the resultant PAOs are promising photocatalysts for CO2 reduction.

Synthesis, characterization, and application of Cu-substituted LaNiO3 perovskites as photocatalysts and/or catalysts for persulfate activation towards pollutant removal

The presence of emerging contaminants in environmental aqueous matrices is an ever-growing problem, since conventional wastewater treatment methods fail to adequately remove them. Therefore, the application of non-conventional methodologies such as advanced oxidation processes is of great importance to tackle this modern problem. Photocatalysis as well as catalytic activation of persulfates are promising techniques in this field as they are capable of eliminating various emerging contaminants, and current research aims to develop new materials that can be utilized for both processes. In this light, the present study focused on the use of a simple sol-gel-combustion methodology to synthesize Cu-substituted LaNiO3 perovskite materials in an attempt to improve the photocatalytic and catalytic performance of pure LaNiO3, using molar ratios of Cu:Ni that have not been previously reported in the literature. The morphological, structural, and optical features of the synthesized materials were characterized by a series of analytical techniques (e.g., X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy, etc.). Also, their performance as photocatalysts, persulfate anion activators and simultaneously as photocatalysts/persulfate anion activators (hybrid) was evaluated by conducting laboratory-scale experiments using phenol (phenolics) as a model emerging contaminant. Interestingly, the results revealed that LaCu0.25Ni0.75O3 exhibited the best efficiency in all the applied processes, which was mainly attributed to the introduction of oxygen vacancies in the structure of the substituted material. The contribution of selected reactive species in the hybrid photocatalytic/catalytic experiments utilizing LaCu0.25Ni0.75O3 as a (photo)catalyst was investigated using appropriate scavengers, and the results suggested that singlet oxygen is the most dominant. Additionally, the stability of all synthesized perovskites was assessed by monitoring the concentration of the leached Cu and/or Ni cations at the end of every applied process. Finally, the reusability of LaCu0.25Ni0.75O3 was evaluated in three consecutive catalytic cycles using the hybrid experiment methodology, as this process demonstrated the best efficiency in terms of phenolics removal, and the results were rather promising.

Enhanced visible-light activation of persulfate for the removal of RhB by supported nano-(C,N,B)-tridoped TiO2/copper foam mixed-crystals

Photocatalytic persulfate activation by TiO2 and its application in sewage treatment have aroused great interest because of its high decontamination ability and strong adaptability, but the low light energy utilization rate and poor recycling of TiO2 limited its practical application. Herein, by using C-, N-, and B-modified TiO2 and immobilizing it on copper foam, we prepared a new and efficient (C,N,B)-TiO2/copper foam photocatalyst with enhanced visible-light activation performance of persulfate for the removal of RhB. It almost completely degraded RhB within 15 min of UV-vis light photocatalysis-assisted persulfate oxidation reaction with TOC removal of 53.17% in 30 min and presented the excellent long-term recyclability and stability, which is much better or comparative than those photocatalysts in the related literatures. (C,N,B)-TiO2/copper foam exhibited the largest apparent rate constant (0.149 min-1), 1.16 times higher than (C,N,B)-TiO2 (0.128 min-1), and 2.40 times higher than that of TiO2 (0.062 min-1), respectively. C,N,B doping modified the crystalline phase of TiO2, narrowed its band gap, and reduced charge-carrier recombination rate. These, together with the synergistic effect between photocatalysis and persulfate activation for enhancing generation of active species, jointly promoted the performance enhancement of TiO2. The 1O2 was the primary oxidation active species for the degradation of RhB, and the radical species (SO4•-, •O2-, and •OH) could further accelerate the photocatalytic activation of persulfate reaction.

4-Methyl-5-vinyl thiazole modified Ni-MOF/g-C3N4/CdS composites for efficient photocatalytic hydrogen evolution without precious metal cocatalysts

The construction of heterojunction systems is an effective way to efficiently generate hydrogen by water photolysis. In this work, Ni-MOF (trimesic acid, (BTC)) and g-C3N4 (denoted as CN) were combined, and then Ni-MOF/CN was modified by 4-Methyl-5-vinyl thiazole (denoted as MVTh). Finally, CdS was loaded on the surface of Ni-MOF/CN/MVTh to prepare the photocatalyst Ni-MOF/g-C3N4/MVTh/CdS (denoted as Ni/CN/M/Cd) with a triangular closed-loop path heterojunction for the first time. As a photocatalyst without precious metal cocatalysts, Ni/CN/M/Cd displayed high H2 evolution (17.844 mmol·g-1·h-1) under an optimum CdS loading of 40 wt%. The H2 evolution rate was approximately 79 times that of Ni-MOF/CN and exceeded those of almost all catalysts based on MOF/CN in the literature. The triangular closed-loop heterojunction formed between Ni-MOF, g-C3N4, and CdS could realize the directional migration of photocarriers and significantly diminished the transfer resistance of carriers. The Ni2+ in Ni-MOF provided many cocatalytic sites for H2 evolution via g-C3N4 and CdS. Furthermore, charge carrier separation in Ni-MOF/CN/CdS improved after the innovative addition of MVTh. This study provides a reference for the construction of a closed-loop heterojunction system without precious metal cocatalysts.

Construction of ZnxCdyS with a 3D Hierarchical Structure for Enhanced Photocatalytic Hydrogen Production from Water Splitting

The ZnxCdyS has been proven to have unique photoelectric properties, but its synthesis method and photocatalytic water cracking performance need to be further improved. In this paper, Cd-MOF@ZIF-8 with a MOF-on-MOF (MOF = metal-organic framework) structure was prepared by a simple ion adsorption method. Then, a CdS/ZnxCdyS heterojunction with a 3D hierarchical structure was formed by solvothermal sulfidation. The prepared catalysts with different Zn/Cd ratios show an improved hydrogen production performance for photocatalytic water splitting, and the hydrogen evolution rate of Zn1Cd1S can reach up to 29.2 mmol·g-1·h-1. The excellent photocatalytic activity not only benefits from ZnxCdyS strong light conversion ability but also is closely related to the hierarchical structure and large specific surface area. A type II heterojunction also plays an important role in the spatial separation of photogenerated carriers. This paper provides a simple and feasible idea for the synthesis of a photocatalyst with a large specific surface area using a MOF-on-MOF synthesis strategy.

WS2 supported PtOx clusters for efficient photocatalytic CO2 reduction: a DFT study

Platinum (Pt) nanoparticles/nanoclusters are some of the most efficient cocatalysts for photocatalytic CO2 reduction. Nevertheless, the produced CO can lead to a poisoning effect due to the strong adsorption strength of the Pt cocatalysts. Using density functional theory, PtOx clusters with variable sizes (Pt4O6, Pt5O8, Pt7O10, and Pt8O13) are selected to load on WS2 (PtOx-WS2) for photocatalytic CO2 conversion. The calculated results demonstrate that PtOx-WS2 are highly stable, and the electron-rich PtOx clusters are beneficial for the photocatalytic CO2 reduction. All the PtOx-WS2 catalysts exhibit efficient photocatalytic performance for CO2 reduction. Especially, Pt4O6-, Pt5O8-, and Pt8O13-WS2 have acceptable or ultra-low ΔGmax (ΔG for the rate-determining step) of 0.57, 0.23, and 0.48 eV to produce CH3OH, HCOOH, and CH4, respectively. The photocatalytic activities of PtOx-WS2 are correlated with the adsorption strength of the key intermediates, and the strong interactions between PtOx-WS2 and *COOH or *HCOO can lower the free energy changes for the first hydrogenation step. More importantly, PtOx-WS2 can also weaken the adsorption strength of *CO and *HCOOH, which are conducive to forming *CHO. This work gives an in-depth insight to design novel catalysts and promote their catalytic activity for photocatalytic CO2 reduction.

A Salt-Resistant and Antibacterial Cu2 ZnSnS4 -Based Hydrogel for High Efficient Photothermal Distillation in Seawater Desalination and Sewage Purification

Solar steam generation technology (SSGT) using unlimited solar energy is regarded as one of the most promising sustainable technologies to produce clean water. However, most of studies on SSGT simply focus on how to improve salt resistance as well as exclude inorganic and organic pollutants in targeted water, and only very limited studies pay attention to the micro-organisms in the collected water. Herein, one porous Cu2 ZnSnS4 -based photothermal hydrogel (CZTS-PH) with antibacterial properties as well as good salt resistance was successfully prepared. The CZTS-PH was measured with the water evaporation rate as high as 3.249 kg m-2  h-1 and photothermal conversion efficiency of 96.3 % under one sun irradiation. Impressively, owing to the amino groups in the skeleton, CZTS-PH can significantly deteriorate the cell membrane and lead to the death of the Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which ensures its long-term stability photothermal conversion and the safety of clean water. Overall, the admired photothermal conversion efficiency, and the excellent salt resistance and antibacterial performance suggest that CZTS-PH could be a promising full-scale device applied in seawater desalination and water purification.

Photocatalytic Synthesis of Ammonia from Pinecone Graphite-Phase Carbon Nitride Loaded with MoS2 Nanosheets as Co-catalysts

Photocatalytic nitrogen fixation is a promising alternative to the Haber-Bosch process to alleviate the energy and environmental crises. Here, we designed a pinecone-shaped graphite-phase carbon nitride (PCN) catalyst supported with MoS₂ nanosheets by a supramolecular self-assembly method. The catalyst shows an excellent photocatalytic nitrogen reduction reaction (PNRR) due to the larger specific surface area and the enhancement of visible light owing to the reduced band gap. Under simulated sunlight, the sample of PCN loaded with 5 wt % MoS₂ nanosheets (MS5%/PCN) shows a PNRR efficiency of 279.41 μmol g^-1 h^-1, which is 14.9 times that of bulk graphite-phase carbon nitride (g-C₃N₄), 4.6 times that of PCN, and 5.4 times that of MoS₂, respectively. The unique pinecone-like structure of MS5%/PCN not only improves the ability of light absorption but also assists in the uniform loading of MoS₂ nanosheets. Likewise, the existence of MoS₂ nanosheets improves the light absorption ability of the catalyst and reduces the impedance of the catalyst. Furthermore, as a co-catalyst, MoS₂ nanosheets can efficiently adsorb nitrogen (N₂) and serve as active N₂ reduction sites. From the perspective of structural design, this work can offer novel solutions for the creation of effective N₂-fixing photocatalysts.

CdS nanocrystallites sensitized ZnO nanosheets for visible light induced sonophotocatalytic/photocatalytic degradation of tetracycline: From experimental results to a generalized model based on machine learning methods

CdS/ZnO nanosheets heterostructures ((x)CdS/ZNs) with different mole ratios of Cd/Zn ((x) = 0.2, 0.4, and 0.6) were synthesized by the impregnation-calcination method. PXRD patterns showed that the (100) diffraction of ZNs was the most significant in the (x)CdS/ZNs heterostructures, and it confirmed that CdS nanoparticles (in cubic phase) occupied the (101) and (002) crystal facets of ZNs with hexagonal wurtzite crystal phase. UV-Vis DRS results indicated that CdS nanoparticles decreased the band gap energy of ZNs (2.80-2.11 eV) and extended the photoactivity of ZNs to the visible light region. The vibrations of ZNs were not observed clearly in the Raman spectra of (x)CdS/ZNs due to the extensive coverage of CdS nanoparticles shielding the deeper-laying ZNs from Raman response. The photocurrent of (0.4) CdS/ZNs photoelectrode reached 33 μA, about 82 times higher than that for ZNs (0.4 μA, 0.1 V vs Ag/AgCl). The formation of an n-n junction at the (0.4) CdS/ZNs reduced the recombination of electron-hole pairs and increased the degradation performance of the as-prepared (0.4) CdS/ZNs heterostructure. The highest percentage removal of tetracycline (TC) in the sonophotocatalytic/photocatalytic processes was obtained by (0.4) CdS/ZNs under visible light. The quenching tests showed that O₂^•-, h⁺, and OH^• were the main active species in the degradation process. The degradation percentage decreased negligibly in the sonophotocatalytic (84%-79%) compared to the photocatalytic (90%-72%) process after four re-using runs due to the presence of ultrasonic waves. For the estimation of degradation behavior, two machine learning methods were applied. The comparison between the ANN and GBRT models evidenced that both models had high prediction accuracy and could be used for predicting and fitting the experimental data of the %removal of TC. The excellent sonophotocatalytic/photocatalytic performance and stability of the fabricated (x)CdS/ZNs catalysts made them promising candidates for wastewater purification.

Construction of Cu7 S4 @CuCo2 O4 Yolk-Shell Microspheres Composite and Elucidation of Its Enhanced Photocatalytic Activity, Mechanism, and Pathway for Carbamazepine Degradation

Water pollution caused by the massive use of medicines has caused significant environmental problems. This work first reports the synthesis and characterization of the Cu₇ S₄ /CuCo₂ O₄ (CS/CCO) yolk-shell microspheres via hydrothermal and annealing methods, and then investigates their photocatalytic performance in removing organic water pollutants. The 10-CS/CCO composite with yolk-shell microspheres exhibits the highest photodegradation rate of carbamazepine (CBZ), reaching 96.3% within 2 h. The 10-CS/CCO also demonstrates more than two times higher photodegradation rates than the pure (Cu₇ S₄ ) CS and (CuCo₂ O₄ ) CCO. This outstanding photocatalytic performance can be attributed to the unique yolk-shell structure and the Z-scheme charge transfer pathway, reducing multiple reflections of the acting light. These factors enhance the light absorption efficiency and efficiently transfer photoexcited charge carriers. In-depth, photocatalytic degradation pathways of CBZ are systematically evaluated via the identification of degradation intermediates with Fukui index calculation. The insights gained from this work can serve as a guideline for developing low-cost and efficient Z-scheme photocatalyst composites with the yolk-shell structure.

Designing Highly Active S-g-C3N4/Te@NiS Ternary Nanocomposites for Antimicrobial Performance, Degradation of Organic Pollutants, and Their Kinetic Study

The current research is about the synthesis of pure nickel sulfide, a series of Te (0, 0.5, 1, 1.5, 2, and 3 wt.%)-doped NiS (Te@NiS) nanoparticles (NPs), and a series of S-g-C3N4 (10, 30, 50, 70, and 80 wt.%)/Te@NiS nanocomposites (NCs), fabricated through a hydrothermal route. XRD and FTIR spectroscopic techniques demonstrated the successful synthesis of NPs and NCs. SEM-EDX images confirmed the flakelike structure and elemental constituents of the fabricated materials. Tauc plots were drawn, to calculate the band gaps of the synthesized samples. Te doping resulted in a significant reduction in the band gap of the NiS NPs. The photocatalytic efficiency of the NPs and NCs was investigated against MB, under sunlight. The results obtained for the photocatalytic activity, showed that 1%Te@NiS nanoparticles have an excellent dye degradation capacity in sunlight. This was made even better by making a series of SGCN/1% Te@NiS nanocomposites with different amounts of S-g-C3N4. When compared to NiS, Te@NiS, SGCN, and 70%SGCN/1%Te@NiS, the 70%SGCN/1%Te@NiS NCs have excellent antifungal ability. The higher impact of SGCN/Te@NiS, may be due to its enhanced ability to disperse and interact with the membranes and intracellular proteins of fungi. The 70%SGCN/1%Te@NiS NCs showed excellent antibacterial and photocatalytic efficiency. Thus, the 70%SGCN/1%Te@NiS NCs might prove fruitful in antibacterial and photocatalytic applications.

Recent advances on catalysts for photocatalytic selective hydrogenation of nitrobenzene to aniline

Selective hydrogenation of nitrobenzene (SHN) is an important approach to synthesize aniline, an essential intermediate with extremely high research significance and value in the fields of textiles, pharmaceuticals and dyes. SHN reaction requires high temperature and high hydrogen pressure via the conventional thermal-driven catalytic process. On the contrary, photocatalysis provides an avenue to achieve high nitrobenzene conversion and high selectivity towards aniline at room temperature and low hydrogen pressure, which is in line with the sustainable development strategies. Designing efficient photocatalysts is a crucial step in SHN. Up to now, several photocatalysts have been explored for photocatalytic SHN, such as TiO2, CdS, Cu/graphene and Eosin Y. In this review, we divide the photocatalysts into three categories based on the characteristics of the light harvesting units, including semiconductors, plasmonic metal-based catalysts and dyes. The recent progress of the three categories of photocatalysts is summarized, the challenges and opportunities are pointed out and the future development prospects are described. It aims to give a clear picture to the catalysis community and stimulate more efforts in this research area.

Photocatalytic Materials Obtained from E-Waste Recycling: Review, Techniques, Critique, and Update

Waste-derived materials obtained from the recovery and recycling of electronic waste (e-waste) such as batteries and printed circuit boards have attracted enormous attention from academia and industry in recent years, especially due to their eco-friendly nature and the massive increment in e-waste due to technological development. Several investigations in the literature have covered the advances achieved so far. Meanwhile, photocatalytic applications are especially of interest since they maintain mutual benefits and can be used for H2 production from solar water splitting based on semiconductor processing as a proper environmentally friendly technique for solar energy conversion. In addition, they can be utilized to degrade a variety of organic and non-organic contaminations. Nonetheless, to the best of the authors’ knowledge, there has not been any comprehensive review that has specifically been focused on e-waste-derived photocatalytic materials. In this regard, the present work is dedicated to thoroughly discussing the related mechanisms, strategies, and methods, as well as the various possible photocatalysts synthesized from e-wastes with some critiques in this field. This brief overview can introduce modern technologies and promising possibilities for e-waste valorization, photocatalytic processes, and new photocatalytic degradation methods of eco-friendly nature. This paper discusses various e-waste-obtained photocatalytic materials, synthesis procedures, and applications, as well as several types of e-waste, derived materials such as TiO2, ZnO, indium tin oxide, and a variety of sulfide- and ferrite-based photocatalytic materials.