Photoelectrocatalytic Materials Research Articles

Ag-TiO2 Photovoltaic Synergistic Field-catalyzed Degradation Performance of Tetracycline

Background: Tetracycline (TC), a commonly used antibiotic, is extensively utilized in the medical sector, leading to a significant annual discharge of tetracycline effluent into the water system, which harms both human health and the environment. Objective: A novel technique was developed to address the issues of photogenerated carrier complexation and photocatalyst immobilization. Compared to traditional photocatalytic photoelectrodes, the suspended catalyst used in the photovoltaic synergy field is more stable and increases the solidliquid contact area between the catalyst and the pollutant. Methods: This paper uses sol-gel-prepared Ag-TiO2 materials for the photoelectric synergistic fieldcatalyzed degradation of TC. The study examined how the Ag doping ratio, calcination conditions, catalyst injection, pH, electrolytes, and electrolyte injection affected photoelectric synergistic fieldcatalyzed degradation. The experiments were performed in a photocomposite field with a constant 50 mA current and a 357 nm UV lamp for 60 minutes. The composites underwent characterization using XRD, TEM, and XPS techniques. Results: Ag-TiO2 photoelectric synergistic field-catalyzed reaction with 357 nm ultraviolet lamp irradiation for 60 min and a constant current of 50 mA degraded 5 mg/LTC under preparation conditions of molar doping ratio of Ti: Ag=100:0.5, roasting temperature of 500 °C, and roasting time of 2 h. The photoelectric synergistic field-catalyzed degradation process achieved a degradation rate of 90.49% for 5 mg/L TC, surpassing the combined degradation rates of electrocatalysis and photocatalysis. The quenching experiments demonstrated that the degradation rate of TC decreased from 90.49% in the absence of a quencher to 53.23%, 42.58%, and 74.52%. The presence of •OH had a more significant impact than h+ and •O2 -. Conclusion: The findings suggest that Ag-TiO2 significantly enhanced the efficacy of photoelectric synergistic field-catalyzed degradation and can be employed to treat high-saline and lowconcentration TC. This establishes a benchmark for using photoelectrocatalytic materials based on titanium in treating organic wastewater.

Photoelectrochemical disinfection efficiency of WO3-based photoanodes: Development of multifunctional photoelectrocatalytic materials

Access to safe water is a growing global concern, with millions lacking acceptable water sources. Photocatalysis offers eco-friendly water remediation, yet its combination with electrocatalysis for both water treatment and hydrogen production remain underexplored. This study investigates UVA LED photoelectrocatalysis using WO3-based photoanodes, alone or in heterojunction with BiVO4, to purify wastewater and co-produce hydrogen. Tests on polluted water streams containing 105 PFU mL−1 of MS2 bacteriophage virus and 106 CFU mL−1 of E. coli reveal that nanostructured WO3 achieves rapid MS2 disinfection within 5 min. (k= 0.80 min−1), with enhanced efficiency over flat counterparts. However, nanostructuring does not improve E. coli inactivation due to bacterium size constraints. These findings advance the design of tandem photoreactors for dual wastewater purification and energy generation.

Constructing Z-Scheme 3D WO3@Co2SnO4 Heterojunction as Dual-Photocathode for Production of H2O2 and In-Situ Degradation of Organic Pollutants

As photoelectrochemical catalyst material, Z-scheme heterojunction 3D WO3@Co2SnO4 composites were designed through a hydrothermal-calcination method. The morphology and structure were characterized by SEM, EDS, XRD, XPS, DRS, and Mott–Schottky analysis, and the photoelectrochemical properties were explored with the transient photocurrent and electrochemical impedance. The construction of Z-scheme heterojunction markedly heightened the separation efficiency of photogenerated electron-hole pairs of WO3 and enhanced the light absorption intensity, retaining the strong redox ability of the photocatalyst. The 3D WO3@Co2SnO4 was used as a photocathode for production of H2O2. Under the optimal reaction conditions, the yield of H2O2 can reach 1335 μmol·L−1·h−1. The results of free radial capture and rotating disc test revealed the existence of direct one-step two-electron and indirect two-step one-electron oxygen reduction to produce H2O2. Based on the excellent H2O2 production performance of the Z-scheme heterojunction photoelectrocatalytic material, 3D WO3@Co2SnO4 and stainless-steel mesh were used to construct a dual-cathode photoelectric-Fenton system for in-situ degradation of a variety of pollutants in water, such as dye (Methyl orange, Rhodamine B), Tetracycline, sulfamethazine, and ciprofloxacin. The fluorescence spectrophotometry was used to detect hydroxyl radicals with terephthalic acid as a probe. Also, the photocatalytic degradation mechanism was revealed, indicating the dual-cathode photoelectron-Fenton system displayed satisfactory potential on degradation of different types of environmental pollutants. This work provided insights for designing high-activity photoelectrocatalytic materials to produce H2O2 and provided possibility for construction of a photoelectric-Fenton system without extra additions.

Retraction: A novel concept and design for highly efficient photoelectrocatalytic materials with high performance, stability, and charge transport properties: development of an innovative next-generation green technology.

[This retracts the article DOI: 10.1039/D3RA05126A.].

Understanding the cascade heterojunction of CuPc/Bi-MOF for photoelectrochemical nitrate reduction.

Herein, a CuPc/Bi-MOF cascade heterojunction is synthesized exhibiting an excellent NH3 yield (7.13 μg h-1 cm-2) and stability. Characterization studies show that the cascade heterostructure with a unique morphology and oxygen vacancies offers new insights into future photoelectrocatalytic material design.

A novel concept and design for highly efficient photoelectrocatalytic materials with high performance, stability, and charge transport properties: development of an innovative next-generation green technology.

In semiconductors, generating charges via catalysis is a highly challenging task and characteristic of heterojunction photoanodes. A dithiophene-4,8-dione spin-coated film layer has a positive effect on the holes (positive charge carriers) for a long time in BHJ films in the solid state of materials. The photoexcited holes created in the BHJ film can persist for long periods of time, which is beneficial for catalytic reactions. In this study, a photoanode is electrically coupled to a hydrogen gas-evolving platinum cathode. When the photoanode is electrically coupled to a H2 gas evolving Pt cathode, curiously long-lived hole polaron states are observed on the timescale of seconds under operational conditions. These long-lived holes play a crucial role in enhancing the hydrogen peroxide oxidation performance of the film overlayer spin-coated onto the photoanode. The spin-coated film overlayer on the photoanode achieves the best oxidation performance for hydrogen peroxide of approximately 6.5 mA cm-2 at 1.23 VRHE without the need of a catalyst. This demonstrates the effectiveness of the overlayer in improving the catalytic performance of the photoanode with a better efficiency of 17.5% when using 851 nm excitation. This indicates that a relatively high percentage of incident photons at that specific wavelength is converted into photocurrent by the photoanode. This approach can lead to more efficient oxidation catalysis as demonstrated in the case of hydrogen peroxide oxidation.

Closed-Loop Multi-Objective Optimization for Cu-Sb-S Photo-Electrocatalytic Materials' Discovery.

Copper antimony sulfides are regarded as promising catalysts for photo-electrochemical water splitting because of their earth abundance and broad light absorption. The unique photoactivity of copper antimony sulfides is dependent on their various crystalline structures and atomic compositions. Here, a closed-loop workflow is built, which explores Cu-Sb-S compositional space to optimize its photo-electrocatalytic hydrogen evolution from water, by integrating a high-throughput robotic platform, characterization techniques, and machine learning (ML) optimization workflow. The multi-objective optimization model discovers optimum experimental conditions after only nine cycles of integrated experiments-machine learning loop. Photocurrent testing at 0V versus reversible hydrogen electrode (RHE) confirms the expected correlation between the materials' properties and photocurrent. An optimum photocurrent of -186µA cm-2 is observed on Cu-Sb-S in the ratio of 9:45:46 in the form of single-layer coating on F-doped SnO2 (FTO) glass with a corresponding bandgap of 1.85eV and 63.2% Cu1+ /Cu species content. The targeted intelligent search reveals a nonobvious CuSbS composition that exhibits 2.3 times greater activity than baseline results from random sampling.

Mn (IV) oxide/Mn (IV) sulfide/poly-2-amino-1-mercaptobenzene for green hydrogen generation

A manganese (IV) oxide (MnO2)–manganese (IV) sulfide (MnS2)/poly-2-amino-1-mercaptobenzene (P2AMB) nanocomposite is prepared through a polymerization reaction (oxidation) and is utilized as a highly photo-electrocatalytic material for green hydrogen generation from sewage water. The manganese (IV) oxide–manganese (IV) sulfide/P2AMB nanocomposite demonstrates remarkable optical properties, characterized by a band gap of 1.81 eV. To promote the water-splitting reaction by the synthesized manganese (IV) oxide–manganese (IV) sulfide/P2AMB nanocomposite photoelectrode, sewage water is utilized as a sacrificial agent to facilitate effectively the generation of hydrogen gas through the evaluation of the current (J ph). At −0.9 V, the J ph and J o values are determined to be −0.33 and −0.2 mA/cm2, respectively. Notably, an optimum J ph value of −0.26 mA/cm2 is observed for incident photons at 340 nm, indicating that light with higher frequency and energy leads to the generation of more electrons from the manganese (IV) oxide–manganese (IV) sulfide/P2AMB nanocomposite and subsequent hydrogen production. Conversely, the lowest J ph value of −0.21 mA/cm2 is obtained at 730 nm, suggesting the influence of infrared waves on the photoelectrode due to the small band gap (1.86 eV) of the materials, as calculated in a previous analysis. This study represents an initial step toward the conversion of wastewater into hydrogen gas, which can serve as a sustainable fuel source for various industrial applications.

Solid Electrolyte Interphase Formation in Tellurium Iodide Perovskites during Electrochemistry and Photoelectrochemistry.

Halide perovskites are promising photoelectrocatalytic materials. Their further development requires understanding of surface processes during electrochemistry. Thin films of tellurium-based vacancy-ordered perovskites with formula A2TeI6, A = Cs, methylammonium (MA), were deposited onto transparent conducting substrates using aerosol-assisted chemical vapor deposition. Thin film stability as electrodes and photoelectrodes was tested in dichloromethane containing tetrabutylammonium PF6 (TBAPF6). Using photoemission spectroscopy, we show that the formation of a solid electrolyte interphase on the surface of the Cs2TeI6, consisting of CsPF6, enhances the stability of the electrode and allows extended chopped-light chronoamperometry measurements at up to 1.1 V with a photocurrent density of 16 μA/cm2. In contrast, (CH3NH3)2TeI6 does not form a passivating layer and rapidly degrades upon identical electrochemical treatment. This demonstrates the importance of surface chemistry in halide perovskite electrochemistry and photoelectrocatalysis.

Manganese doping regulated the built-in electric field of FeBTC for enhanced photoelectrocatalytic hydrolysis

MOF-based Mott Schottky heterojunction has been researched as a promising photoelectrocatalytic material for oxygen evolution reaction (OER), but activity is severely limited by built-in electric field (BIEF). In this study, trace Mn doping strategy is used to enhance the BIEF of FeBTC/NIF, and the energy level configuration is also adjusted. Prepared Mn-FeBTC/NIF has excellent photoelectric coupling catalytic capability, requiring 309 mV overpotential to excite 100 mA cm−2 under illumination and maintaining stability for up to 48 h under different light conditions. Catalytic excellence stems from the elevated BIEF, which means Mn accelerated charge transport, modulated the charge density around the active center, effectively improving the catalytic activity. Moreover, the addition of Mn can effectively improve the conduction band (CB) and valence band (VB), reduce the energy band gap, improve the light absorption capacity and enhance the photocatalytic performance. This work provides new ideas for increasing the BIEF of heterojunction materials.

Photo-electrocatalytic degradation of tylosin by TiO2 nanotube modified photoelectrode: Synthesis, kinetics, and mechanism investigations

Semiconductor photo-electrocatalytic technology is considered as an efficient and environmentally friendly wastewater treatment and energy production technology. TiO2 NTs is widely used in the field of photoelectricity catalysis because of its chemical stability and good recycling. In this paper, g-C3N4 and Ag nanoparticles were deposited on the surface of TiO2 NTs by solid-phase sublimation and electrodeposition method to prepare Ag/g-C3N4/TiO2 NTs composite photo-electrocatalytic materials. The Ag/g-C3N4/TiO2 NTs composites showed significant photo-electrocatalytic activity compared with the single component materials. The mechanism of enhanced catalytic activity is that the tight interface formed between Ag, g-C3N4 and TiO2 NTs, facilitating the photoinduced electron migration from g-C3N4 to TiO2 NTs and inhibiting the recombination of carrier pairs under the cooperative mechanism of photoelectric catalysis. The results of five cycle experiments show that Ag/g-C3N4 /TiO2 NTs has good stability. LC-MS and ECOSAR analysis results indicate that Ag/g-C3N4/TiO2 NTs photo-electrocatalytic system can be safely used for wastewater degradation treatment.

Recent Developments in Conductive Polymer‐Based Electro‐/Photoelectrocatalytic Materials for Effective Hydrogen/Oxygen Evolution Reactions: A Review

AbstractCurrently, a substantially greener energy source such as hydrogen fuel cell is an alternative to fossil fuel sources, and much research has been dedicated to achieving highly efficient hydrogen (H2 gas) generation. In this line, electrochemical water splitting that involves hydrogen and oxygen evolution reactions (HER and OER, respectively) is considered to be the greener and most effective hydrogen‐generating procedure with only water as a by‐product. However, in the process of successful OER/HER, it is extremely demanding for electrocatalysts with high activity, stability and cost‐effectiveness for the water splitting process. Herein, the review proposed promising electrocatalysts such as conductive polymers (CPs) with enhanced catalytic effect with the polymer encapsulation of catalytic material that provides an increase in charge transfer kinetics both in OER/HER. Also, the review highlights the OER and HER mechanism of conducting polymers and their effect on the synergism was discussed in detail. Also, the review detailed the reduced overpotentials, importance and enhancement of catalytic efficiency with various polymers reported in both OER and HER. Here, the choice of polymers can matrix with the inorganic active sites to prevent them from aggregation and the water splitting carried out over the electrode surface results in good conductivity to charge transfer from the electrode to the active sites. In addition, the review discussed the polymers induces the photon effect with photoelectrocatalytic water splitting. Thus, the combing effect with conducting polymers and the materials with catalytic active centers open up a new kind of electrocatalyst for synthesis.

Colloidal Inorganic Ligand-Capped Nanocrystals: Fundamentals, Status, and Insights into Advanced Functional Nanodevices.

Colloidal nanocrystals (NCs) are intriguing building blocks for assembling various functional thin films and devices. The electronic, optoelectronic, and thermoelectric applications of solution-processed, inorganic ligand (IL)-capped colloidal NCs are especially promising as the performance of related devices can substantially outperform their organic ligand-capped counterparts. This in turn highlights the significance of preparing IL-capped NC dispersions. The replacement of initial bulky and insulating ligands capped on NCs with short and conductive inorganic ones is a critical step in solution-phase ligand exchange for preparing IL-capped NCs. Solution-phase ligand exchange is extremely appealing due to the highly concentrated NC inks with completed ligand exchange and homogeneous ligand coverage on the NC surface. In this review, the state-of-the-art of IL-capped NCs derived from solution-phase inorganic ligand exchange (SPILE) reactions are comprehensively reviewed. First, a general overview of the development and recent advancements of the synthesis of IL-capped colloidal NCs, mechanisms of SPILE, elementary reaction principles, surface chemistry, and advanced characterizations is provided. Second, a series of important factors in the SPILE process are offered, followed by an illustration of how properties of NC dispersions evolve after ILE. Third, surface modifications of perovskite NCs with use of inorganic reagents are overviewed. They are necessary because perovskite NCs cannot withstand polar solvents or undergo SPILE due to their soft ionic nature. Fourth, an overview of the research progresses in utilizing IL-capped NCs for a wide range of applications is presented, including NC synthesis, NC solid and film fabrication techniques, field effect transistors, photodetectors, photovoltaic devices, thermoelectric, and photoelectrocatalytic materials. Finally, the review concludes by outlining the remaining challenges in this field and proposing promising directions to further promote the development of IL-capped NCs in practical application in the future.

Awakening the Photoelectrochemical Activity of α‐SnWO4 Photoanodes with Extraordinary Crystallinity Induced by Reductive Annealing

Oxide‐based photoelectrodes for solar water splitting have gained growing attention because of their decent stability and cost‐effectiveness. Particularly, α‐SnWO4 has been regarded as a potential next‐generation light absorbing material due to the predicted favorable bandgap of 1.9 eV. Herein, the investigation and amelioration of the crystallinity as a performance dominating factor to the α‐SnWO4‐based photoanode are demonstrated. The improvement is attributed to a unique crystallization process induced by the formation of oxygen vacancies in the reductive atmosphere at 500 °C. The sample exhibits notably enhanced visible‐light absorption and an improved charge transport property. Electrochemical measurements reveal a cathodic shift of the flat‐band potential, corresponding to the impacted band position. The photocurrent is enhanced from 0.03 to 0.42 mA cm−2 (AM1.5, 1.23 VRHE). Such a new treatment can be used as an effective tool for developing α‐SnWO4 into efficient photoelectrocatalytic (PEC) materials.

Fabrication of Six Manganese Containing Polyoxometalate Modified Graphite C3N4 Nanosheets Catalysts Used to Catalyze Water Decomposition

With the increase in gas population, the demand for clean and renewable energy is increasing. Hydrogen energy has a high combustion conversion energy while water is its combustion product. In recent years, a way to convert water into hydrogen and oxygen has been found by human beings inspired by plant photosynthesis. However, water decomposition consumes a significant amount of energy and is expensive. People expect to obtain a water decomposition catalyst with low cost and high efficiency. This work selected a six-manganese containing polyoxometalate with a similar structure characteristic to photosynthesizing PSII to fabricate with graphite C3N4 nanosheets for the construction of composite film (Mn6SiW/g-C3N4NSs) electrode via layer by layer self-assembly technology, which was used for the photo-electrochemical decomposition of water under visible light conditions. The binary composite film electrode displayed good catalytic efficiency. The photoelectric density of the composite electrode is 46 μA/cm2 (at 1.23 V vs. Ag/AgCl) and 239 μA/cm2 (at 1.5 V vs. Ag/AgCl). Compared with the g-C3N4NSs electrode alone, the photoelectric density of the composite electrode increased by 1 time. The reason is attributed to the fact that Mn6SiW has a similar structure characteristic to photosynthesizing PSII and high electron transferability. The construction of the composite film containing low-cost Mn6SiW to modify g-C3N4NSs can effectively improve the photocatalytic decomposition of water, thus this study provides valuable reference information for the development of low-cost and high-performance photo-electrocatalytic materials.

(Invited) Design of Photoelectrocatalytic Materials and Interfaces for Artificial Photosynthesis

The agenda of the Sustainable Development Goals of the United Nations calls for an increase in the share of renewable energy worldwide in the next ten years. Artificial photosynthesis, which is the conversion of sunlight, water, and carbon dioxide into chemicals, offers a promising alternative. Energy is stored in chemical bonds of molecules such as hydrogen or hydrocarbons, and this energy can be released upon need. Semiconductor materials and catalysts are the most important constituents of artificial photosynthetic systems. Herein, we will present an approach to design strategies for the synthesis and integration of photoelectrocatalytic materials for selective and stable operation.

Atomic layer deposition of photoelectrocatalytic material on 3D-printed nanocarbon structures

Combining two advanced layer-by-layer manufacturing techniques, low-temperature atomic layer deposition of MoS2on a customizable 3D-printed nanocarbon surface, for photoelectrochemical energy conversion system.

A CeO2 Semiconductor as a Photocatalytic and Photoelectrocatalytic Material for the Remediation of Pollutants in Industrial Wastewater: A Review

The direct discharge of industrial wastewater into the environment results in serious contamination. Photocatalytic treatment with the application of sunlight and its enhancement by coupling with electrocatalytic degradation offers an inexpensive and green technology enabling the total removal of refractory pollutants such as surfactants, pharmaceuticals, pesticides, textile dyes, and heavy metals, from industrial wastewater. Among metal oxide—semiconductors, cerium dioxide (CeO2) is one of the photocatalysts most commonly applied in pollutant degradation. CeO2 exhibits promising photocatalytic activity. Nonetheless, the position of conduction bands (CB) and valence bands (VB) in CeO2 limits its application as an efficient photocatalyst utilizing solar energy. Its photocatalytic activity in wastewater treatment can be improved by various modification techniques, including changes in morphology, doping with metal cation dopants and non-metal dopants, coupling with other semiconductors, and combining it with carbon supporting materials. This paper presents a general overview of CeO2 application as a single or composite photocatalyst in the treatment of various pollutants. The photocatalytic characteristics of CeO2 and its composites are described. The main photocatalytic reactions with the participation of CeO2 under UV and VIS irradiation are presented. This review summarizes the existing knowledge, with a particular focus on the main experimental conditions employed in the photocatalytic and photoelectrocatalytic degradation of various pollutants with the application of CeO2 as a single and composite photocatalyst.

Fabrication of Dandelion-like p-p Type Heterostructure of Ag2O@CoO for Bifunctional Photoelectrocatalytic Performance.

A novel three-dimensional purple dandelion-like hierarchical Ag2O@CoO heterojunction with an appropriate redox potential was constructed by chemical precipitation of Ag2O nanoparticle on flower-like CoO. By feat of this hierarchical structure, the Ag2O@CoO photocathode showed significantly high photoelectroreduction activities toward p-nitrophenol (p-NP) and Cr(VI). The high performance of Ag2O@CoO was mainly attributed to the specific structural characteristics and synergistic effect of each chemical component. This hierarchical structure could effectively increase the specific surface area, provide more exposed active edges, and be beneficial for multiple light reflection/scattering channels and light utilization efficiency. The introduction of Ag2O optimized the composition and further improved the band structure, resulting in an improved separation of photogenerated electrons and holes. The unique photocathode achieves a removal efficiency of 86% for photoelectrocatalytic p-NP degradation after 120 min and 95% for Cr(VI) after 40 min under visible light irradiation with excellent stability. This research provided a simple way for the synthesis of photoelectrocatalytic material with potential applications in the field of environmental governance with visible light illumination.

Structural limiting factors of mixed-valent tin oxides in photoelectrochemical application: A comparative exploration

Abstract Photoelectrocatalytic (PEC) materials for harvesting solar energy can be discovered from existing photocatalytic semiconductors. Nonetheless, mixed valence tin oxides, a group of widely reported visible light active photocatalysts, can hardly be developed into efficient PEC photoelectrodes. To overcome this difficulty by clarifying its origin, two typical mixed valence tin oxides, Sn2+:SnO2 microrods and porous Sn3O4 particles were deliberately prepared as the models. Sn2+:SnO2 microrods of less porosity exhibited a photocurrent over ten times higher than Sn3O4 particles. Photo-electrochemical impedance spectroscopy revealed this was due to their charge kinetics difference, specifically the internal transport/transfer responding to the morphology. Moreover, hydroxyl residuals from synthesis were found to be very inhibitive for the PEC efficiency as well, which was in coherence with our TGA and Raman spectroscopic study. These finding experimentally proved the necessity of reconsidering the surface area, crystallinity, and defects when developing photocatalysts into efficient PEC structures.