Plasma-Enhanced Ni atom-modulated Co-OH to Promote Surface Charge Transfer of CuWO4 photoanode for Efficient Solar Hydrogen Evolution

The high charge recombination and slow transfer kinetics of photoanode remains to be great challenges in photo-electrochemistry (PEC). While, the semiconductor (CuWO4)/layered double-metal hydroxides (LDHs)/plasma coupling strategy is identified as one of the effective methods to enhance the PEC behaviors. The LDHs act as hole-conducting layers to promote interfacial catalytic reactions of PEC and release charges from the CuWO4 photoanode, which effectively enhances charge separation and boosts kinetic processes. Metallic Ag nanoparticles enhances light-absorbing capacity of the photoanode, as well as improves charge separation and kinetics of the photoanode utilizing the surface plasmon resonance (SPR) effect for increasing carrier groups and facilitatingcharge separation. The study shows that the CuWO4/NiCo-LDH/Ag photoanode prepared via as-mentioned coupling strategy exhibits a potential photocurrent density of 2.84 mA·cm−2 at 1.23 V vs. RHE, which is 9.2 times higher than that of the pristine CuWO4 (0.31 mA·cm-2) in phosphate buffered electrolyte. Moreover, it is determined that a special charge-trapping states (surface state) exists during the charge transfer process, which plays an indispensable role for the charge storage and transfer. Density Functional Theory (DFT) calculations validate that the introduction of NiCo-LDH and Ag facilitates charge transfer, whereas the modulation of the rate-determining steps (RDS) boosts the overall efficiency of the reaction. This study presents a guiding design approach for regulating PEC behavior of the semiconductor/LDHs/plasma strategy.