Size- and facet-dependent photoelectrochemical properties of CuO crystals

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2023-05, Vol.11 (17), p.5857-5866
• Main Authors: Ma, Hsueh-Heng, Huang, Michael H
• Format: Article
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d3tc00673e

For size- and facet-dependent photoelectrochemical (PEC) activity comparison, Cu 2 O cubes with average sizes of 58, 213, and 441 nm, octahedra, rhombic dodecahedra, and cuboctahedra were synthesized. The crystals exhibit clear optical size and facet dependence. However, a mixture of large and small cubes produces a homogenous solution color. Under front-side illumination with particles deposited on an indium tin oxide (ITO) glass electrode, cubes show the best photon-to-current efficiency. Unexpectedly, octahedra have the lowest charge transfer resistance, but exhibit very weak photosensitivity. The stacked rhombic dodecahedra yield a weak PEC performance from hindered hole transport, but photocurrent is greatly enhanced with back-side illumination. Cuboctahedra exposing {100} and {111} faces have intermediate PEC responses. Under back-side illumination, photocurrents also increase greatly for 213 and 441 nm cubes. The PEC performance of Cu 2 O crystals exhibits high correlation to the exposed faces, but band diagrams constructed from Mott-Schottky measurements do not agree with the PEC activity order. A shorter path for hole transport from Cu 2 O to ITO electrode is critical to PEC performance. While Cu 2 O cubes show the best photon-to-current efficiency under front-side illumination, photocurrent is greatly enhanced for rhombic dodecahedra under back-side illumination with more facile charge transport.