Enhanced Photoelectrochemical\nWater Splitting Using\nNiMoO₄/BiVO₄/Sn-Doped WO₃ Double\nHeterojunction Photoanodes

Abstract

Efficient photoelectrochemical (PEC) water splitting\nsystems in\nphotoelectrodes are primarily challenged by electron–hole pair\nrecombination. Constructing a heterostructure is an effective strategy\nto overcome this issue and to enhance PEC efficiency. In this study,\nwe integrated NiMoO₄, known for its proper electrocatalytic\nconductivity, into a BiVO₄/Sn-doped WO₃ heterojunction\nusing solution-based hydrothermal and spin-coating methods, forming\nan innovative double heterojunction concept. The resulting NiMoO₄/BiVO₄/Sn:WO₃ triple-layer heterojunction\nphotoanode exhibits a photocurrent density of 2.06 mA cm^–2 in a potassium borate buffer (KBi) electrolyte at 1.23 V vs RHE,\noutperforming the bilayer BiVO₄/Sn:WO₃ heterojunction\n(1.45 mA cm^–2) and Sn:WO₃ photoanodes\n(0.55 mA cm^–2) by approximately 1.4 and 3.7 times,\nrespectively. Remarkably, the NiMoO₄/BiVO₄/Sn:WO₃ double heterojunction photoanode exhibits notable stability,\nshowing only an approximate 30% reduction in initial photocurrent\ndensity after 10 h of measurement in the KBi electrolyte without a\nhole scavenger. This stability is attributed to the excellent corrosion\nresistance of the thin NiMoO₄ layer, effectively protecting\nthe bilayer BiVO₄/Sn:WO₃ heterojunction photoanode\nfrom photocorrosion. Our findings show how this novel double heterojunction,\nestablished through simple and cost-effective solution-based methods,\noffers a promising approach to enhancing PEC water splitting applications.