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The increasing demand for clean hydrogen necessitates the rapid development of efficient photoanodes to catalyze the water oxidation half‐reaction effectively. Here a strategy is introduced to fabricate photoanodes that synergistically combine and leverage the properties of porous Ti‐doped hematite (Ti‐Fe2O3) and graphitic carbon nitride (g‐C3N4) nanosheets anchored with in situ grown Ni‐doped CoP co‐catalyst (Ni‐CoP). The resulting hybrid photoanodes exhibit >7 times higher photocurrent density at +1.23 VRHE compared with Ti‐Fe2O3 photoanodes. Comprehensive characterization techniques, including ambient photoemission spectroscopy, intensity‐modulated photocurrent spectroscopy, and transient absorption spectroscopy complementarily reveal the key impact of g‐C3N4 in these composites with enhanced solar oxygen evolution reaction: The incorporation of g‐C3N4 leads to enhanced charge separation through a type‐II heterojunction, thereby increasing the hole flux at the surface, and extending the charge carrier lifetime to the ms‐s range needed for water oxidation. Additionally, g‐C3N4 facilitates efficient transfer of photogenerated holes to the fine Ni‐CoP nanoparticles confined in the graphitic matrix for a boosted oxygen evolution reaction. These findings highlight the advantages of complex heterostructure photoanodes and demonstrate a new application of g‐C3N4 as a multifunctional support of co‐catalysts for future photoanodes with enhanced performance. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C3N4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C3N4, which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C3N4/rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs3Bi2Br9, resulting in a g-C3N4/rGO/Cs3Bi2Br9 composite. This leads to a remarkable increase in photocatalytic conversion of CO2 and H2O to CO, H2 and CH4 at rates of 54.3 (±2.0) μmole− g−1 h−1, surpassing that of pure Cs3Bi2Br9 (11.2 ± 0.4 μmole− g−1 h−1) and bulk g-C3N4 (5.5 ± 0.5 μmole− g−1 h−1). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C3N4 and Cs3Bi2Br9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs3Bi2Br9) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C3N4) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals. [ABSTRACT FROM AUTHOR]

Among the various photoanode materials investigated for photoelectrochemical water splitting cells, TiO2 stands out due to its abundance, stability, and favorable valence band edge for water oxidation. In this study, the importance of introducing and combining oxygen and titanium vacancy point defects in anatase TiO2 photoanodes to improve their performance is unveiled, achieving a photocurrent density of 0.73 (±0.015) mA cm−2 at +1.23 VRHE under 100 mW cm−2 of simulated sunlight or 26.4 mA cm−2 at +1.23 VRHE under 100 mW cm−2 of 365 nm light. The characterization by X‐ray photoelectron spectroscopy, surface photovoltage, and electron paramagnetic resonance demonstrates that these oxygen and titanium vacancies can have both collective and localized positive effects on the material, leading to a narrowing of the bandgap, an increase in donor density, and an increase in hydroxyl groups on the surface of TiO2. These result in enhanced light absorption, conductivity, and photovoltage, as well as a more negative flat‐band potential and increase in hole flux to the semiconductor–electrolyte interface. These findings provide valuable insights into the role of point defects in modulating the properties of TiO2 and have important implications for the development of high‐performance TiO2‐based devices. [ABSTRACT FROM AUTHOR]

BiVO4 has attracted wide attention for oxygen‐evolution photoanodes in water‐splitting photoelectrochemical devices. However, its performance is hampered by electron‐hole recombination at surface states. Herein, partially oxidized two‐dimensional (2D) bismuthene is developed as an effective, stable, functional interlayer between BiVO4 and the archetypal NiFeOOH co‐catalyst. Comprehensive (photo)electrochemical and surface photovoltage characterizations show that NiFeOOH can effectively increase the lifetime of photogenerated holes by passivating hole trap states of BiVO4; however, it is limited in influencing electron trap states related to oxygen vacancies (VO). Loading bismuthene on BiVO4 photoanodes increases the density of VO that are beneficial for the oxygen evolution reaction via the formation of oxy/hydroxyl‐based water oxidation intermediates at the surface. Moreover, bismuthene increases interfacial band bending and fills the VO‐related electron traps, leading to more efficient charge extraction. With the synergistic interaction of bismuthene and NiFeOOH on BiVO4, this composite photoanode achieves a 5.8‐fold increase in photocurrent compared to bare BiVO4 reaching a stable 3.4 (±0.2) mA cm–2 at a low bias of +0.8 VRHE or 4.7(±0.2) mA cm–2 at +1.23 VRHE. The use of 2D bismuthene as functional interlayer provides a new strategy to enhance the performance of photoanodes. [ABSTRACT FROM AUTHOR]

Photocatalytic CO 2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C 3 N 4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C 3 N 4 , which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C 3 N 4 /rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs 3 Bi 2 Br 9 , resulting in a g-C 3 N 4 /rGO/Cs 3 Bi 2 Br 9 composite. This leads to a remarkable increase in photocatalytic conversion of CO 2 and H 2 O to CO, H 2 and CH 4 at rates of 54.3 (±2.0) μmol e - g -1 h -1 , surpassing that of pure Cs 3 Bi 2 Br 9 (11.2 ± 0.4 μmol e - g -1 h -1 ) and bulk g-C 3 N 4 (5.5 ± 0.5 μmol e - g -1 h -1 ). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C 3 N 4 and Cs 3 Bi 2 Br 9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs 3 Bi 2 Br 9 ) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C 3 N 4 ) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO 2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Achieving highly performant photoanodes for oxygen evolution is key to developing photoelectrochemical devices for solar water splitting. In this work, BiVO 4 photoanodes are enhanced with a series of core-shell structured bimetallic nickel-cobalt phosphides (MPs), and key insights into the role of co-catalysts are provided. The best BiVO 4 /Ni 1.5 Co 0.5 P and BiVO 4 /Ni 0.5 Co 1.5 P photoanodes achieve a 3.5-fold increase in photocurrent compared with bare BiVO 4 . It is discovered that this enhanced performance arises from a synergy between work function, catalytic activity, and capacitive ability of the MPs. Distribution of relaxation times analysis reveals that the contact between the MPs, BiVO 4 , and the electrolyte gives rise to three routes for hole injection into the electrolyte, all of which are significantly improved by the presence of a second metal cation in the co-catalyst. Kinetic studies demonstrate that the significantly improved interfacial charge injection is due to a lower charge-transfer resistance, enhanced oxygen-evolution reaction kinetics, and larger surface hole concentrations, providing deeper insights into the carrier dynamics in these photoanode/co-catalyst systems for their rational design., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Lead-free halide perovskite derivative Cs 3 Bi 2 Br 9 has recently been found to possess optoelectronic properties suitable for photocatalytic CO 2 reduction reactions to CO. However, further work needs to be performed to boost charge separation for improving the overall efficiency of the photocatalyst. This report demonstrates the synthesis of a hybrid inorganic/organic heterojunction between Cs 3 Bi 2 Br 9 and g-C 3 N 4 at different ratios, achieved by growing Cs 3 Bi 2 Br 9 crystals on the surface of g-C 3 N 4 using a straightforward antisolvent crystallization method. The synthesized powders showed enhanced gas-phase photocatalytic CO 2 reduction in the absence of hole scavengers of 14.22 (±1.24) μmol CO g -1 h -1 with 40 wt % Cs 3 Bi 2 Br 9 compared with 1.89 (±0.72) and 5.58 (±0.14) μmol CO g -1 h -1 for pure g-C 3 N 4 and Cs 3 Bi 2 Br 9 , respectively. Photoelectrochemical measurements also showed enhanced photocurrent in the 40 wt % Cs 3 Bi 2 Br 9 composite, demonstrating enhanced charge separation. In addition, stability tests demonstrated structural stability upon the formation of a heterojunction, even after 15 h of illumination. Band structure alignment and selective metal deposition studies indicated the formation of a direct Z-scheme heterojunction between the two semiconductors, which boosted charge separation. These findings support the potential of hybrid organic/inorganic g-C 3 N 4 /Cs 3 Bi 2 Br 9 Z-scheme photocatalyst for enhanced CO 2 photocatalytic activity and improved stability., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

CO 2 photocatalytic conversion into value-added fuels through solar energy is a promising way of storing renewable energy while simultaneously reducing the concentration of CO 2 in the atmosphere. Lead-based halide perovskites have recently shown great potential in various applications such as solar cells, optoelectronics, and photocatalysis. Even though they show high performance, the high toxicity of Pb 2+ along with poor stability under ambient conditions restrains the application of these materials in photocatalysis. In this respect, we developed an in situ assembly strategy to fabricate the lead-free double perovskite Cs 2 AgBiBr 6 on a 2D bismuthene nanosheet prepared by a ligand-assisted reprecipitation method for a liquid-phase CO 2 photocatalytic reduction reaction. The composite improved the production and selectivity of the eight-electron CH 4 pathway compared with the two-electron CO pathway, storing more of the light energy harvested by the photocatalyst. The Cs 2 AgBiBr 6 /bismuthene composite shows a photocatalytic activity of 1.49(±0.16) μmol g -1 h -1 CH 4 , 0.67(±0.14) μmol g -1 h -1 CO, and 0.75(±0.20) μmol g -1 h -1 H 2 , with a CH 4 selectivity of 81(±1)% on an electron basis with 1 sun. The improved performance is attributed to the enhanced charge separation and suppressed electron-hole recombination due to good interfacial contact between the perovskite and bismuthene promoted by the synthesis method., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)