Elucidating the Role of Surface Energetics on Charge Separation during Photoelectrochemical Water Splitting

• Published in: ACS catalysis Vol. 12; no. 23; pp. 14727 - 14734
• Main Authors: Pan, Zhenhua, Nandal, Vikas, Pihosh, Yuriy, Higashi, Tomohiro, Liu, Tian, Röhr, Jason A., Seki, Kazuhiko, Chu, Chiheng, Domen, Kazunari, Katayama, Kenji
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02.12.2022
• Subjects: surface energetics; cocatalyst; charge separation; water splitting; photocatalyst
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.2c04225

Efficient photoelectrochemical (PEC) water splitting requires charge separation and extraction from a photoactive semiconductor. Such a charge transport process is widely believed to be dictated by the bulk energetics of the semiconductor. However, its dependence on surface energetics along the semiconductor/electrolyte interface remains an open question. Here, we elucidate the influence of surface energetics on the performance of a well-established Mo-doped BiVO4 photoanode whose surface energetics are regulated by the facet-selective cocatalyst loading. Surprisingly, photodeposition of RhO x and CoO x cocatalysts onto the {010} and {110} facets, respectively, strongly enhanced the charge-separation efficiency, in addition to improving the injection efficiency for water oxidation. Detailed optoelectrical simulations confirm that the synergistic enhancement of charge separation originates from the distinct effects of the cocatalyst loading on the surface energetics. This insight into the fundamental charge-separation mechanism in PEC cells provides a perspective for cell design and operation.