As the development of oxygen evolution co-catalysts (OECs) is being actively undertaken, the tailored integration of those OECs with photoanodes is expected to be a plausible avenue for achieving highly efficient solar-assisted water splitting. Here, we demonstrate that a black phosphorene (BP) layer, inserted between the OEC and BiVO 4 can improve the photoelectrochemical performance of pre-optimized OEC/BiVO 4 (OEC: NiOOH, MnO x, and CoOOH) systems by 1.2∼1.6-fold, while the OEC overlayer, in turn, can suppress BP self-oxidation to achieve a high durability. A photocurrent density of 4.48 mA·cm −2 at 1.23 V vs reversible hydrogen electrode (RHE) is achieved by the NiOOH/BP/BiVO 4 photoanode. It is found that the intrinsic p -type BP can boost hole extraction from BiVO 4 and prolong holes trapping lifetime on BiVO 4 surface. This work sheds light on the design of BP-based devices for application in solar to fuel conversion, and also suggests a promising nexus between semiconductor and electrocatalyst.

Solar energy-assisted water oxidative hydrogen peroxide (H2O2) production on an anode combined with H2 production on a cathode increases the value of solar water splitting, but the challenge of the dominant oxidative product, O2, needs to be overcome. Here, we report a SnO2–x overlayer coated BiVO4 photoanode, which demonstrates the great ability to near-completely suppress O2 evolution for photoelectrochemical (PEC) H2O oxidative H2O2 evolution. Based on the surface hole accumulation measured by surface photovoltage, downward quasi-hole Fermi energy at the photoanode/electrolyte interface and thermodynamic Gibbs free energy between 2-electron and 4-electron competitive reactions, we are able to consider the photoinduced holes of BiVO4 that migrate to the SnO2–x overlayer kinetically favor H2O2 evolution with great selectivity by reduced band bending. The formation of H2O2 may be mediated by the formation of hydroxyl radicals (OH·), from 1-electron water oxidation reactions, as evidenced by spin-trapping electron paramagnetic resonance (EPR) studies conducted herein. In addition to the H2O oxidative H2O2 evolution from PEC water splitting, the SnO2–x /BiVO4 photoanode can also inhibit H2O2 decomposition into O2 under either electrocatalysis or photocatalysis conditions for continuous H2O2 accumulation. Overall, the SnO2–x /BiVO4 photoanode achieves a Faraday efficiency (FE) of over 86% for H2O2 generation in a wide potential region (0.6–2.1 V vs reversible hydrogen electrode (RHE)) and an H2O2 evolution rate averaging 0.825 μmol/min/cm2 at 1.23 V vs RHE under AM 1.5 illumination, corresponding to a solar to H2O2 efficiency of ∼5.6%; this performance surpasses almost all previous solar energy-assisted H2O2 evolution performances. Because of the simultaneous production of H2O2 and H2 by solar water splitting in the PEC cells, our results highlight a potentially greener and more cost-effective approach for “solar-to-fuel” conversion.

Propelled by photovoltaic cell and electrolysis research, the photoelectrochemical (PEC) water splitting system has been tuned to produce a high-value-added product and be a competitive strategy for solar-to-fuel conversion. The hydrogen peroxide (H2O2) produced by a two-electron pathway from water oxidation has recently been the focus of redesigned PEC technologies, which will be significant and important for unassisted PEC systems that use only light, water, and oxygen to simultaneously produce electricity and high-value-added H2O2 by redox coupling of H2O. Moreover, it is expected to increase the efficiency of solar water splitting through the H2O2 intermediate as it easily disproportionates to O2 and H2O. Here, we present our prospects for an exciting new direction for solar water oxidation through H2O2 production and a mechanism for guiding material design, which will provide a considerable possibility for the revitalization of PEC water splitting.

Inspired by the great success of graphite in lithium‐ion batteries, anode materials that undergo an intercalation mechanism are considered to provide stable and reversible electrochemical sodium‐ion storage for sodium‐ion battery (SIB) applications. Though MoS2 is a promising 2D material for SIBs, it suffers from deformation of its layered structure during repeated intercalation of Na+, resulting in undesirable electrochemical behaviors. In this study, vertically oriented MoS2 on nitrogenous reduced graphene oxide sheets (VO‐MoS2/N‐RGO) is presented with designed spatial geometries, including sheet density and height, which can deliver a remarkably high reversible capacity of 255 mA h g−1 at a current density of 0.2 A g−1 and 245 mA h g−1 at a current density of 1 A g−1, with a total fluctuation of 5.35% over 1300 cycles. These results are superior to those obtained with well‐developed hard carbon structures. Furthermore, a SIB full cell composed of the optimized VO‐MoS2/N‐RGO anode and a Na2V3(PO4)3 cathode reaches a specific capacity of 262 mA h g−1 (based on the anode mass) during 50 cycles, with an operated voltage range of 2.4 V, demonstrating the potentially rewarding SIB performance, which is useful for further battery development.

Exploration of proficient electrocatalyst from earth-abundant nonprecious metals in lieu of noble metal-based catalysts to obtain clean hydrogen energy through large-scale electrochemical water splitting is still an ongoing challenge. Herein, iron-doped nickel cobalt phosphide nanoplate arrays grown on a carbon cloth (NiCoFe x P/CC) are fabricated using a simple hydrothermal route, followed by phosphorization. The electrochemical analysis demonstrates that the NiCoFe x P/CC electrode possesses high electrocatalytic activity for water splitting in alkaline medium. Benefits from the synergistic effect between the metal centers, two-dimensional porous nanoplates, and unique threedimensional electrode configuration of NiCoFe x P/CC provide small overpotentials of 39 at 10 mA cm −2 and 275 mV at 50 mA cm −2 to drive the hydrogen evolution reaction and oxygen evolution reaction, respectively. Furthermore, the assembled two-electrode (NiCoFe x P/ CC∥NiCoFe x P/CC) alkaline water electrolyzer can achieve 10 mA cm −2 current density at 1.51 V. Remarkably, it can maintain stable electrolysis over 150 h. The excellent activity and stability of this catalyst is proved to be a economical substitute of commercial noble metal-based catalysts in technologies relevant to renewable energy.