NdCo₃ Molecular\nCatalyst Coupled with a\nBiVO₄ Photoanode for Photoelectrochemical Water Splitting

Abstract

Photoelectrochemical water splitting\nis a promising strategy\nfor\nharvesting and converting solar energy to green hydrogen energy. However,\nthe current inferior performance restricts further improvement of\nthe solar-to-hydrogen efficiency. In this work, a molecular catalyst\n[NdCo₃(btp-3H)₂(Ac)₂(NO₃)₂] (NO₃)·2H₂O (referred to\nas NdCo₃ herein) was deposited onto a porous BiVO₄ photoanode using a drop-casting method, and the molecular catalyst\nwas held in place on the BiVO₄ surface via intermolecular\nforces. The photoelectrochemical water oxidation performance of the\nBiVO₄/NdCo₃ photoanode reached 2.25 mA cm^–2 at 1.23 V vs RHE under AM 1.5G illumination (100\nmW cm^–2), which was much higher than the pristine\nBiVO₄ photoanode (1.49 mA cm^–2). The\nenhanced performance could be attributed to the improvement of the\ncharge carrier transfer efficiency, resulting in the acceleration\nof the water oxidation kinetics and inhibiting charge carrier recombination.\nIn addition, the electrocatalytic properties of the homogeneous system\nwere also studied. It was found that a heterogeneous catalytic film\nwas formed due to the water solubility of NdCo₃, which\nenabled a long electrolysis process to be maintained. The electrocatalytic\nperformance of a homogeneous system reached 1 mA cm^–2 at 2.31 V vs RHE and was different from the heterogeneous catalytic\nfilm (reached 1 mA cm^–2 at 2.10 V vs RHE). This\nintegrated system showed that the combination of a molecular catalyst\nwith a photoelectrode helped to promote charge-carrier transport and\nseparation, reducing the amount of charge-carrier recombination. Our\napproach may be applicable to other materials, helping to provide\nideas for developing material combinations capable of achieving greater\nsolar-to-hydrogen efficiencies.