(594f) The Novel Electrocatalyst/Semiconductor Photoelectrodes for Efficient Photoelectrochemical Water Splitting

Water splitting by solar-driven photoelectrochemical (PEC) reactions has been broadly recognized as one of the most promising chemical method for sustainable energy conversion and storage systems. Effective integration of semiconductor and electrocatalyst is critical for fabricating efficient PEC devices. However, this is a big challenge, because the introduction of interfacial recombination centers on the electrocatalyst/semiconductor junction result in charge recombination. Moreover, considering the advantages of electrocatalysts with ultrathin morphology, the rational design of electrocatalyst/semiconductor architecture to improve the hydrogen evolution reaction (HER) or oxygen evolution reaction (OER) kinetics without sacrificing light harvesting is of significance to achieve efficient PEC system. Recently, we found that amorphous materials synthesized by a facile electrodeposition method can serve as highly efficient electrocatalysts for efficient photoelectrochemical water splitting.

Transition metal chalcogenides (TMC) are considered as the promising HER electrocatalysts. The electrodeposition method can produce various TMC HER catalysts such as CoSe₂, Ni_0.85Se, NiSe₂ and CoSe_x etc. Also we realized the rational design of a novel 3D p-Si/NiCoSe_x core/shell nanopillar (NP) array photocathode by uniform photo-assisted electrodeposition of NiCoSe_x electrocatalyst on bamboo shoots-like Si NP array backbones. We demonstrate its enhanced PEC performance with a photocurrent density of -37.5 mA/cm² at 0 V (vs. RHE) under simulated 100 mW/cm² (1 Sun) with an AM 1.5 G filter, which is the highest value reported for p-type Si photocathodes. The synergic effects of the excellent light harvesting of Si NP array core and the good optical transparency, as well as excellent electrocatalytic activity of NiCoSe_x shell boost the production and utilization of photo-generated electrons [3-5].

Furthermore, metal hydroxides are excellent electracatalysts for water splitting. It was found that amorphous cobalt-iron hydroxide (CoFe-H) nanosheets by the electrodeposition can be simply integrated with BiVO₄ semiconductor to construct CoFe-H/BiVO₄ photoanodes that exhibit a significantly enhanced photocurrent density of 2.48 mA/cm² (at 1.23 V vs. RHE) and a much lower onset potential of 0.23 V (vs. RHE) for PEC-OER. Careful electrochemical and optical studies reveal that the improved OER kinetics and high-quality interface at the CoFe-H/BiVO₄ junction, as well as the excellent optical transparency of CoFe-H nanosheets, contribute to the high PEC performance.

Our work proves that the integrated electrocatalyst/semiconductor photoelectrodes are active for high performance solar-driven photoelectrochemical water splitting. We think high-quality electrocatalyst/semiconductor interface and excellent optical transparency of electrocatalysts result in the high PEC performance.