Photoelectrocatalytic Reaction Research Articles

Interface and Defect Engineering in 3D Co3O4‐Ov/TiO2 to Boost Simultaneous Removal of BPA and Cr(VI) upon Photoelectrocatalytic/Peroxymonosulfate (PEC/PMS) System

AbstractThe combination of photoelectrocatalytic (PEC) and peroxymonosulfate (PMS) is an innovative strategy for environmental treatment. And fabricating a highly efficient photoelectrode is the most pivotal factor in PEC reactions. This study designs an advanced Co3O4‐Ov/TiO2 photoelectrode by a dual‐modification strategy encompassing interface engineering and defect engineering. The photoelectric characterization validates the synergy of oxygen vacancies and dual heterojunctions. Simulated electron density distribution and Kelvin probe force microscopy (KPFM) elucidate the charge transfer pathway between Co3O4‐Ov and TiO2. 1O2 and SO4 .− are confirmed to be primarily responsible for the BPA oxidation in PEC/PMS system by radical scavenger experiments and the EPR technique. And the attack sites of BPA are precisely identified based on the Fukui index. Furthermore, density functional theory (DFT) calculations testify that Co3O4‐Ov can improve the adsorption capacity of PMS and reduce the energy barrier of the reaction process, while XPS analysis showed Co3+/Co2+ redox couple can accelerate PMS activation. Enhanced anode oxidation can effectively promote cathode reduction and consequently Co3O4‐Ov/TiO2‐PMS/PEC system presents a superior removal of both pollutants within only 15 min with fast kinetics (0.15 min−1 for BPA, 0.29 min−1 for Cr(VI)). This work provides unique insight into designing a highly efficient PMS/PEC system for simultaneous pollutant treatment.

Semiconductor Nanoporous Anodic Alumina Photonic Crystals as a Model Photoelectrocatalytic Platform for Solar Light‐Driven Reactions

In this study, nanoporous anodic alumina distributed‐Bragg reflectors (NAA–DBRs) functionalized with tungsten trioxide (WO3) are used as prototype photoelectrocatalysts (PEC) for harnessing the slow photon effect to maximize photon‐to‐electron conversion efficiency under UV–visible–NIR illumination. NAA–DBR structures are structurally engineered by anodization, where their characteristic photonic stopband is precisely tuned along specific positions of the UV–visible spectrum. Subsequent atomic layer deposition is employed to coat the inner surface of these porous structures with WO3 semiconductor layers. Upon the application of overpotential bias, these platforms reveal excellent electron–hole pair separation to boost photoelectrocatalytic reactions. Photoelectrochemical degradation of methylene blue is used as a model reaction to elucidate enhancements associated with structural and optoelectronic arrangements. Notably, precise spectral alignment between the photonic stopband's red edge and the absorbance band of methylene blue enhances the degradation performance through the slow photon effect. Applying an overpotential bias further improves the photodegradation performance through efficient charge separation. These systems outperform comparable structures in this model reaction, achieving a maximum kinetic rate of 13.7 ± 2.0 h−1. The findings create new opportunities to develop high‐performing PEC technologies harnessing light–matter interactions.

Photoelectrocatalytic CO2 Reduction to Formate Using a BiVO4/ZIF-8 Heterojunction.

Converting CO2 into high-value chemical fuels through green photoelectrocatalytic reaction path is considered as a potential strategy to solve energy and environmental problems. In this work, BiVO4/ZIF-8 heterojunctions are prepared by in-situ synthesis of ZIF-8 nanocrystals with unique pore structure on the surface of BiVO4. The experimental results show that the silkworm pupa-like BiVO4 is successfully combined with porous ZIF-8, and the introduction of ZIF-8 can provide more sites for CO2 capture. The optimal composite ratio of 4 : 1-BiVO4/ZIF-8 exhibits excellent CO2 reduction activity and the lowest electrochemical transport resistance. In the electrocatalytic system, the formate Faraday efficiency of 4 : 1-BiVO4/ZIF-8 at -1.0 V vs. RHE is 82.60 %. Furthermore, in the photoelectrocatalytic system, the Faraday efficiency increases to 91.24 % at -0.9 V vs. RHE, which is 10.8 times higher than the pristine BiVO4. The results show that photoelectric synergism can not only reduce energy consumption, but also improve the Faraday efficiency of formate. In addition, the current density did not decrease during 34 h electrolysis, showing long-term stability. This work highlights the importance of the construction of heterojunction to improve the performance of photoelectrocatalytic CO2 reduction.

Photoelectrocatalytic allylic C–H oxidation to allylic alcohols coupled with hydrogen evolution

Allylic C–H bond oxidation of cycloolefins to allylic alcohols has attracted tremendous attention owing to its widespread application in pharmaceuticals production and natural synthesis. However, the production of allylic alcohols still suffers from the challenges of unsatisfactory selectivity and harsh conditions. Herein, we report the sustainable photoelectrocatalytic (PEC) allylic C–H oxidation to allylic alcohols, achieving the oxidation of cyclohexene to 2-cyclohexenol with a selectivity of 97.2 %. We reveal the reaction pathway wherein photogenerated holes and OH– synergistically activate cyclohexene to carbocation intermediates, and these intermediates combine with OH– to produce 2-cyclohexenol. Additionally, the mechanism by enriching OH– in local area of photoanode surface to enhance PEC performance is uncovered. Furthermore, we designed a self-powered PEC reaction system, attaining a 2-cyclohexenol productivity of 11.95 μmol h–1 (selectivity > 97 %) coupled with a H2 productivity of 1.44 mL h–1, demonstrating the application potential of this new strategy.

Exfoliated g-C3N4-CdS-MXene an efficient all-solid-state Z-type heterojunction serving as efficient photo/electro/photoeletro catalyst for oxygen evolution reaction and dye degradation under visible light at low bias voltage

The rational design of highly active catalysts for the photo/electro/photoelectro catalytic O2 evolution reaction (OER) and water treatment plays a crucial role in the development of sustainable energy generation and environment remediation technologies. Catalysts which are effective in solar light at a low external bias potential are in great demand. Herein, a novel catalyst consisting of all-solid-state Z-scheme g-C3N4-CdS-MXene heterojunction has been designed for photo/electro/photoelectro catalytic reactions. g-C3N4-CdS-MXene exhibited excellent photocatalytic efficiency towards Methylene Blue degradation under simulated solar light irradiation and superb electrocatalytic and photoelectron catalytic efficiency for OER. This catalyst showed high OER performance with an early onset potential of 1.58 V, a low overpotential of 350 mV (at 10 mA cm−2), and low value of Tafel slope (98 mV dec−1). When OER was combined with the photoelectro catalytic reaction for Methylene Blue degradation, g-C3N4-CdS-MXene demonstrated an exceptional photoelectro catalytic performance by degrading 100 % Methylene Blue within 4 min under solar light irradiation at a very low bias of 350 mV. This catalyst also exhibited its capability to degrade various dyes used in textile industries. This work provides an interesting strategy for simultaneous O2 production and efficient dye degradation for environmental and energy engineering.

Tetragonal/orthorhombic phase Bi2WO6 homojunction for photoelectrochemical degradation of rhodamine B with high efficiency

Photoelectrochemical (PEC) degradation of organic pollutants to CO2 and H2O is a promising strategy to solve the growing environmental problems. Bismuth tungstate (Bi2WO6) has attracted much attention due to its good chemical stability and moderate conduction band valence band position. However, the PEC activity of Bi2WO6 catalysts is greatly limited due to its rapidly complex electron-hole. This article reports a rational low-cost design that successfully prepares tetragonal/orthorhombic Bi2WO6 homojunction on FTO conductive glass substrates through a simple two-step solvothermal method, significantly enhancing the PEC performance. The study investigated the effectiveness of photoelectrochemical degradation of the recalcitrant organic pollutant Rhodamine B (RhB) and conducted an in-depth exploration of the photoelectrocatalytic reaction process and mechanism. The experimental results indicate that the homojunction achieves a degradation rate of up to 100 % for the recalcitrant organic pollutant RhB within 30 minutes, significantly surpassing that of single-phase Bi2WO6, and at the same time the sample maintains good stability after five cycles of operation. Further analysis of the capture experiments indicates that holes (h+) and superoxide radicals (·O2⁻) are the primary active species responsible for RhB degradation. This study not only provides new insights into the design of high-efficiency photoelectrode, but also offers new solutions for environmental pollution control.

Hydrophobic-treated yolk-shell SnS2@CSs Z-scheme confinement reactor for solar-electro-driven hydrogen peroxide production in neutral media

The diffusion and adsorption properties of the O2/H2O corpuscles at active sites play a crucial role in the fast photo-electrocatalytic reaction of hydrogen peroxide (H2O2) production. Herein, SnS2 nanosheets with abundant interfacial boundaries and large specific areas are encapsulated into hollow mesoporous carbon spheres (CSs) with flexibility, producing a yolk-shell SnS2@CSs Z-scheme photocatalyst. The nanoconfined microenvironment of SnS2@CSs could enrich O2/H2O in catalyst cavities, which allows sufficient internal O2 transfer, improving the surface chemistry of catalytic O2 to O2− conversion and increasing reaction kinetics. By shaping the mixture of SnS2@CSs and polytetrafluoroethylene (PTFE) on carbon felt (CF) using the vacuum filtration method, the natural air-breathing gas diffusion photoelectrode (AGPE) was prepared, and it can achieve an accumulated concentration of H2O2 about 12 mM after a 10 h stability test from pure water at natural pH without using electrolyte and sacrificial agents. The H2O2 product is upgraded through one downstream route of conversion of H2O2 to sodium perborate. The improved H2O2 production performance could be ascribed to the combination of the confinement effect of SnS2@CSs and the rich triple phase interfaces with the continuous hydrophobic layer and hydrophilic layer to synergistically modulate the photoelectron catalytic microenvironment, which enhanced the transfer of O2 mass and offered a stronger affinity to oxygen bubbles. The strategy of combining the confined material with the air-breathing gas diffusion electrode equips a wide practical range of applications for the synthesis of high-yield hydrogen peroxide.

Photoelectrocatalysis degradation of P-aminophenol using PbO2-TiO2 heterojunction electrode: Catalytic, theoretical calculating and mechanism

To lengthen the lifetime and extend the potential commercial applications of lead dioxide electrode. Herein, PbO2–TiO2 heterostructured electrodes were fabricated via direct current electrodeposition and the surface of the electrode was characterized by electron microscopy (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The PbO2–TiO2 heterostructure electrode could produce an obvious photocurrent under UV irradiation, indicating a photoelectrocatalytic reaction. The PbO2–TiO2 heterostructured electrode was examined using density functional theory calculations(DFT). Work function(WF) confirmed that the applied electric field is conducive to the movement of photoelectrons, which promotes the photoelectrocatalysis effect. The nudged elastic band(NEB) results showed that the PbO2–TiO2 heterostructure electrode can promote the formation of •OH by reducing the activation barrier. The PbO2–TiO2 electrode was used as an anode to treat P-aminophenol (PAP) wastewater simulated wastewater and real PAP wastewater via photoelectrocatalytic degradation. The PbO2–TiO2 electrode effectively removes chemical oxygen demand (COD) from actual wastewater was 54.93 %,The after-treated Pb2+ concentration (0.037 mg·L−1) was lower than China’s wastewater discharge standard (1 mg·L−1). Finally, the degradation pathway of PAP was determined based on the intermediates detected using gas chromatography–mass spectrometry and the reactive sites of PAP were predicted using the Fukui function.These results suggest that the photoelectrocatalysis degradation of PAP using electrodes is feasible.

Preparation of ternary composite film TiO2/Fe2O3/Ti3C2 for photoelectrocatalytic degradation of organic pollutants and bacterial inactivation in water

Global water pollution is a serious problem, and photoelectrocatalytic technology is expected to be a new path to solve it. In this study, a ternary composite TiO2/Fe2O3/Ti3C2 photoanode was synthesized by hydrothermal, water bath, and spin-coating methods for the photoelectrocatalytic degradation of pollutants and disinfection in water. The results showed that the composite film was capable of degrading 96.74 % of MB solution within 120 min and killing 99.43 % of E. coli and 100.00 % of S. aureus within 30 min. Furthermore, the MB degradation efficiency remained nearly constant throughout the 35th cyclic photoelectrocatalytic reaction, demonstrating the adequate stability of the photoanode. The outstanding performance of the film is attributed to (1) the large specific surface area due to the unique structure of composite, (2) low surface-interface resistance and improvement of photogenerated carrier separation and migration because of heterojunction structure and co-catalyst Ti3C2 with high conductivity. It is also proved that the four radicals ·O2-, ·OH, ∙Cl, ∙ClO play a role in the system. This study provides a practical direction for designing future photocatalytic materials and advancing the treatment of pollutants in water.

Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min−1 and 0.01416 min−1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology.

Recent progress in atomically precise metal nanoclusters for photocatalytic application.

Photocatalysis is a widely recognized green and sustainable technology that can harness inexhaustible solar energy to carry out chemical reactions, offering the opportunity to mitigate environmental issues and the energy crisis. Photocatalysts with wide spectral response and rapid charge transfer capability are crucial for highly efficient photocatalytic activity. Atomically precise metal nanoclusters (NCs), an emerging atomic-level material, have attracted great interests owing to their ultrasmall size, unique atomic stacking, abundant surface active sites, and quantum confinement effect. In particular, the molecule-like discrete electronic energy level endows them with small-band-gap semiconductor behavior, which allows for photoexcitation in order to generate electrons and holes to participate in the photoredox reaction. In addition, metal NCs exhibit strong light-harvesting ability in the wide spectral UV-near IR region, and the diversity of optical absorption properties can be precisely regulated by the composition and structure. These merits make metal NCs ideal candidates for photocatalysis. In this review, the recent advances in atomically-precise metal NCs for photocatalytic application are summarized, including photocatalytic water splitting, CO2 reduction, organic transformation, photoelectrocatalytic reactions, N2 fixation and H2O2 production. In addition, the strategy for promoting photostability, charge transfer and separation efficiency of metal NCs is highlighted. Finally, a perspective on the challenges and opportunities for NCs-based photocatalysts is provided.

Study of the Hydrogen Evolution Reaction on Macroscopic Snse-Based Photoelectrodes

Conversion of solar energy to valuable chemicals by using photoelectrochemical (PEC) techniques such as water splitting, carbon dioxide reduction reaction (CO2RR) and nitrogen reduction reaction (N2RR), are promising methods to solve the issues of energy crisis and global warming [1-2]. Two-dimensional (2D) and layered semiconductors, for example, transition metal chalcogenides (TMCs), metal oxides and MXenes have attracted great attention for PEC applications because of their unique properties, such as high carrier mobility, tunable bandgap, anisotropic carrier transport, and high specific surface area [3]. Our review indicates that, i) 2D and layered semiconductors can be applied for different PEC applications, both in oxidation and reduction reactions, and have ability to give higher performance in water reduction (i.e., hydrogen evolution reaction, HER) than in the other ones. ii) TMCs have been the most studied material with higher performance than the others. However, high PEC performance was achieved only on single crystal TMCs or in microelectrochemical cells, implying a limitation in the scalability of this solar energy conversion approach [4]. There is a clear need to study macroelectrodes prepared from polycrystalline semiconductors and identify the opportunities and barriers for their applications. In our study [5], tin(II) selenide (SnSe) was used as a photoelectrode for PEC HER since it has not been widely investigated for this PEC application. We fabricated SnSe macroscopic photocathodes by depositing SnSe flakes, made from commercial SnSe crystals using a liquid phase exfoliation (LPE) method, on glassy carbon. The as-received SnSe crystals were exfoliated in isopropanol/water mixtures (IPA/H2O) and pure IPA, respectively. Pure IPA was found to be the optimal solvent to prepare flakes and for achieving the highest PEC activity. An additional size separation to make three different size fractions of SnSe crystals served to further optimize the LPE process. Electrodes prepared from the largest flakes showed the highest photocurrent density of 2.44 ± 0.65 mA cm–2 at –0.74 V vs. RHE. The photodeposited Pt co-catalyst on SnSe surface further accelerated the PEC HER activity to 4.39 ± 0.15 mA cm–2. Intensity modulated photocurrent spectroscopy results manifested that the Pt co-catalyst enhanced the charge transfer process and suppressed charge carrier recombination. Overall, the solvent for exfoliation, the edge density of SnSe nanoflakes, immobilization method, and Pt co-catalyst affected the PEC HER performance of SnSe. These results indicate the merit of employing SnSe electrodes for PEC HER and inspire us to explore other photoelectrocatalytic reactions on the macroscopic exfoliated SnSe electrodes.

Photoelectrocatalytic Processes of TiO2 Film: The Dominating Factors for the Degradation of Methyl Orange and the Understanding of Mechanism.

Various thicknesses of TiO2 films were prepared by the sol-gel method and spin-coating process. These prepared TiO2 films exhibit thickness-dependent photoelectrochemical performance. The 1.09-μm-thickTiO2 film with 20 spin-coating layers (TiO2-20) exhibits the highest short circuit current of 0.21 mAcm-2 and open circuit voltage of 0.58 V among all samples and exhibits a low PEC reaction energy barrier and fast kinetic process. Photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TiO2 films was carried out under UV light. The roles of bias, film thickness, pH value, and ion properties were systematically studied because they are the four most important factors dominating the PEC performance of TiO2 films. The optimized values of bias, film thickness, and pH are 1.0 V, 1.09 μm, and 12, respectively, which were obtained according to the data of the PEC degradation of MO. The effect of ion properties on the PEC efficiency of TiO2-20 was also analyzed by using halide as targeted ions. The "activated" halide ions significantly promoted the PEC efficiency and the order was determined as Br > Cl > F. The PEC efficiency increased with increasing Cl content, up until the optimized value of 30 × 10-3 M. Finally, a complete degradation of MO by TiO2-20 was achieved in 1.5 h, with total optimization of the four factors: 1.0 V bias, 1.09-μm-thick, pH 12, and 30 × 10-3 M Cl ion content. The roles of reactive oxygen species and electric charge of photoelectrodes were also explored based on photoelectrochemical characterizations and membrane-separated reactors. Hydrogen peroxide, superoxide radical, and hydroxyl radical were found responsible for the decolorization of MO.

Incorporating photocatalytic fuel cell with dual S-scheme CuBi2O4/Bi2WO6/ZnO NRA photoanode for energy recuperation from municipal wastewater treatment under sunlight

Photocatalytic fuel cell (PFC) utilized the chemical energy contained in the molecules by combining photocatalytic treatment of wastewater with fuel cell electrochemical reaction. Herein, a PFC system with a novel dual S-scheme heterojunction CuBi2O4/Bi2WO6/ZnO nanorod array (CBO/BWO/ZnO NRA) composite photoanode was first constructed for municipal wastewater treatment accompanied with electricity generation under direct sunlight. The introduction of CBO and BWO not only contributed to the narrowing of the band gap which enabled the ZnO NRA to utilize sunlight more efficiently, but also led to the excellent electron-hole segregating capability. The 10% CBO/BWO/ZnO NRA composite photoanode achieved a significantly ameliorated electrical power with maximum power density of 7.707 µW/cm2, which was superior to those pristine ZnO NRA and BWO/ZnO NRA binary materials. The composite photoanode was then tested for its mineralization activity in the municipal wastewater and 98.4% of COD removal was acquired within 90 min. The main attribution that conducive to its spectacular performance in municipal wastewater treatment came from the one-dimensional nanorod array architecture along with the synergistic relation among the three efficient components in the CBO/BWO/ZnO NRA heterojunction that can effectively hinder the charge carrier recombination rate and facilitated a good route for electron transport. The composite photoanode also manifested good stability in five cyclic runs. The dual S-scheme CBO/BWO/ZnO NRA enabled the free active species partook in the photoelectrocatalytic reaction and the working principle of PFC system was also speculated. Additionally, phytotoxicity findings signified that the comprehensive toxicity of municipal wastewater was eliminated after PFC treatment.

Graphene oxide partially exfoliated from carbon cloth: A new Paradigm of photocathode for Solar–Driven photoelectrochemistry

A critical factor limiting the photoelectrocatalytic reaction rate over semiconductors is severe photogenerated charge–carrier recombination, which is well–circumvented in this study by using graphene oxide (GO) partially exfoliated from carbon cloth (CC) as the photoelectrode. A kinetic model is proposed for the first time to rationalize the outstanding photoelectrochemical activity of GO/CC by accounting for the photoexcited charge carrier generation induced by harvesting of broadband sunlight mostly by GO. The photogenerated electron–hole pairs are thereby close to the GO/CC–electrolyte liquid junction and are rectified by surface band bending to flow in opposite directions. The charge recombination is hence largely suppressed and further quenched considering the high–lying conduction band extremum of GO, which favors injection of the photoexcited electrons into the electrolyte. As an important result of efficient charge separation, the photogenerated charge carriers relax mostly via the reaction with H2O2 in the electrolyte, as evidenced by the steady–state photocurrent density of GO/CC depending linearly on the light intensity and by the transient time constant of the time–resolved photocurrent response of GO/CC to chopped solar irradiation being primarily dictated by the diffusion and dissociative adsorption rate of H2O2 on GO/CC.

Improved aquaculture wastewater treatment and concomitant power generation in a photoelectrocatalytic fuel cell equipped with S-scheme Fe2WO6/ZnO nanorod arrays photoanode and NiFe2O4 cathode

The treatment of aquaculture wastewater involved the elimination of refractory organics and total nitrogen (TN) concurrently was one of the towering challenges in wastewater treatment. In this work, aquaculture wastewater comprised of tetracycline (TC) and TN as well as its energy recovery was recuperated in a visible light responsive photocatalytic fuel cell (PFC) system. The S-scheme Fe2WO6 nanoparticle-anchored on ZnO nanorod array (Fe2WO6/ZNA) photoanode and NiFe2O4 nanoflower-loaded on carbon felt (NiFe2O4/CF) cathode spanned photoelectrocatalysis and catalytic chlorination, conducing both contaminant removal and power production. In the presence of optimized conditions (0.5 M Cl−, dual constructed electrodes, solution pH 7), the system exhibited a maximum power density of 1.820 mW cm−2 and removed 100 % and 88.4 % of TC and TN in 120 min, respectively. The yielded small amount of NH4+ and NO3– can also destroy by NiFe2O4/CF cathode because of its large surface area and rapid charge carrier transport. Moreover, the toxicity results testified that the treated aquaculture organic seemed to have no harmful impact on zebrafish model after PFC-chlorine treatment. The mechanism involving S-scheme Fe2WO6/ZNA-NiFe2O4/CF electrodes and PFC-chlorination enabled the core species Cl and OH partook in the photoelectrocatalytic reaction. Based on the trapping agent, electron spin resonance and liquid chromatography mass spectrometry test outcomes, the degradation pathway of TC and its by-product was also postulated.

Tuning the Surface Properties of CuO Films Using the Precursor Aging Approach for Enhanced Photoelectrocatalytic Reactions

AbstractThe surface properties of semiconductors have a significant influence on their photoelectrocatalytic efficiency. This research presents a precursor aging method for tuning the surface properties of CuO films, for enhanced catalytic response. A precursor solution made using copper acetate, polyethylene glycol (PEG) 400, and diethanolamine, and aged for 1, 40, 80, 120, 150, 180, and 250 days is used in each case to fabricate CuO photocathodes via the dip‐coating method. The films fabricated using the 1‐day‐old precursor reveal compact and homogeneous nanoparticles. The films eventually get tuned to yield highly porous and rougher surfaces after aging the precursors for 180–250 days. The film's bandgap decreases by 9% after 180–250 days of precursor aging. Photocathodes prepared using the 180‐day‐old precursor produce the optimum photocurrent density of 1.6 mA cm−2 at 0.35 V versus reversible hydrogen electrode (RHE), representing a 196% increase relative to the films fabricated using the 1‐day‐old solution. They also produce an anodic onset potential shift of 260 mV. This improved photoelectrocatalytic response is due to the porous morphology of the films, which produces a larger surface area that enhances light absorption, increases active sites for catalytic reactions, and reduces charge transfer resistance at the photocathode‐electrolyte interface.

Photoelectrocatalytic degradation of wastewater and simultaneous synthesis of NH3 on Fe-CNTs-supported octahedral Cu2O composite nanocatalysts

Fe-core carbon nanotubes (Fe-CNTs) were produced by vapor deposition using coal as a carbon source. Then, octahedral copper oxide nanoparticles (Cu2ONO) (prepared by solvent reduction method) were loaded on Fe-CNTs by hydrothermal method to prepare the composite catalyst Cu2ONO/Fe-CNTs. While characterizing (TEM, XRD, FTIR, XPS, N2-TPD, BET, etc.) the material structure, the performance of Cu2ONO/Fe-CNTs in photoelectrocatalytic (PEC) degradation of cotton pulp black liquor (CPBL an organic wastewater with high CODCr) and simultaneous synthesis of NH3 was studied. The PEC reaction was carried out in an H-type reactor. CPBL was oxidized at the anode to produce H+, CO2, H2O and other small molecules, where H+ passes through a proton exchange membrane and is reduced with N2 to produce NH3 at the cathode. After 4 h of reaction, the CODCr removal rate of CPBL in the anode chamber reached 95.42%, and the yield of NH3 in the cathode chamber reached 9.06 mmol L−1 cm−2. The dual purpose of synthesizing NH3 while degrading wastewater was achieved.

Energy-oriented utilization from organic wastewater: Directional photoelectrocatalytic conversion of phenol to C1 fuels

To solve the problems of energy consumption, carbon emissions and pollution simultaneously, the directional conversion of phenol to hydrocarbon fuels through a pathway of “phenol → CO2 → HCO3–→HCOOH” was explored, with self-supplied CO2 as both carbon-based transition carrier and electron acceptor. In this economic approach, photoelectrocatalytic (PEC) deep mineralization of phenol was realized on the photoanode to provide CO2, together with the waste electrons from mineralization, was PEC converted into formate as the major liquid product on photocathode under an applied potential of 3 V and simulated sunlight. The total carbon utilization efficiency of phenol to hydrocarbons is 6.76%, and the conversion efficiency of formic acid is as high as 94.8% within 8 h PEC reaction. The integrated cell achieved the recovery of 2.75% waste electrons from phenol oxidation to produce liquid fuel. This work provides a promising “carbon neutral” strategy, which is important for realizing pollutant resource utilization and alleviating energy shortage.

CsPbBr3/platinum and CsPbBr3/graphite hybrid photoelectrodes for carbon dioxide conversion to oxalic acid

CsPbBr3 halide perovskites have been recently received a lot of interest in the field of photo and electro catalysis, solar cells, and photodetectors due to their tunable band gap, large absorption coefficient and high carriers’ mobility. However, CsPbBr3 poor water stability limits its real application and the development of related devices. In this work, hybrid CsPbBr3/platinum (Pt) and CsPbBr3/graphite (C) photo-electrodes are employed, for the first time, in aqueous environment for the photo-electrochemical CO2 conversion to liquid products. Hybrid photo-electrodes were prepared depositing CsPbBr3 by spin coating and sputtering Pt or C on top of it to obtain a homogeneous protective layer with the same thickness. Thanks to the Pt and C layers, the instability of the perovskite in water environment is overcome and the new hybrid electrodes obtained still showed the ability to absorb light in the visible region producing photocurrent. The as-obtained photo-electrodes demonstrated energy band values suitable to reduce carbon dioxide by photo-electrocatalytic reaction in water environment. As main results, these hybrid electrodes produced complex organic molecules such as oxalic acid with Faradic efficiencies close to 44% (at −0.8 V vs Ag/AgCl) using graphite in combination with CsPbBr3.