Effect of W–Mo Composition on the Interfacial Electronic Structure and Photoelectrochemical Performance of CuW1–xMoxO4/BiVO4 Heterojunctions

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High Resolution Image Download MS PowerPoint Slide Photoelectrochemical (PEC) water splitting is a promising approach to sustainable hydrogen production. Among various strategies to enhance PEC efficiency, engineering semiconductor heterojunctions has emerged as an effective method to improve charge separation and suppress recombination. This study employs density functional theory (DFT) to investigate CuW 1– x Mo x O 4 /BiVO 4 heterojunctions as a function of the level of W–Mo substitution, focusing on how interfacial energetics affect electronic properties and PEC performance. Although exploring different surface facets is an initial and important strategy to modify surface structure, focusing on the most stable facet shows that changes in surface composition on that facet significantly affect interfacial energetics. WO 2 -terminated surfaces of (010) CuW 1– x Mo x O 4 result in a Type-III (broken gap) alignment, whereas CuO 2 -terminated surfaces promote a favorable Type-II band alignment that enables effective charge separation. Modifications of bulk and (sub)surface composition through W–Mo substitution modulate the electrostatics potential and interfacial coupling, further enhancing charge separation efficiency. These findings provide critical insights into the atomic-scale mechanisms governing PEC activity and suggest design strategies for tuning surface energetics in complex ternary metal oxide photoelectrodes.