Low Voltage Deposition of NiCoV Layered Double Hydroxide Nanosheets on BiVO₄ Photoanodes for Photoelectrochemical Water Splitting

Abstract

The escalation of energy and environmental crises highlights the increasingly critical role of clean energy. In this study, ternary NiCoV layered double hydroxide nanosheets were electrodeposited onto the BiVO 4 photoanode using a low bias voltage, enhancing the hole injection efficiency on the BiVO 4 surface. The introduction of low-valent V species, serving as effective electron donors, promotes metal species coupling and enhances the catalytic performance. A heterojunction structure, comprising BiVO 4 and layered double hydroxides-(LDH) nanosheets, was formed to improve the photoelectrochemical (PEC) water splitting capabilities of the BiVO 4 photoanode. The photocurrent density of BiVO 4 /NiCo-LDH/-0.1 V photoelectrode prepared under low bias voltage is 2.64 mA/cm 2 , which is 1.27 times that of the BiVO 4 /NiCo-LDH/-0.7 V photoelectrode (2.08 mA/cm 2 ) and 2.15 times that of bare BiVO 4 (1.23 mA/cm 2 ). After introducing the V species, the photocurrent density of BiVO 4 /NiCoV-LDH prepared under low bias was 3.32 mA/cm 2 , which is 1.25 times and 1.59 times higher than that of BiVO 4 /NiCo-LDH/-0.1 V and BiVO 4 /NiCo-LDH/-0.7 V photoelectrodes, respectively. The surface efficiency (η surface ) of BiVO 4 /NiCoV-LDH is 71%, representing a 2.45-fold increase over that of pure BiVO 4 . The improvement of PEC performance is attributed to the synergistic catalytic effect of V species with Ni and Co species in the NiCoV-LDH nanocatalyst prepared under low bias voltage as well as the unique crystal and amorphous structure that provides more active sites. This study introduces a catalyst for photoelectrochemical water splitting and paves the way for the innovative design of other multimetal hydroxides.