Effect of sputter-coated platinum on the photostability of nanoporous sol–gel CuO thin film photocathodes

Titelangaben

Zhang, Hongyang ; Khanlary, Mahshad ; von der Haar, Frederike ; Wu, Qingyang ; Hofmann, Anja ; Zhang, Yaohao ; Tian, Chuanmu ; Marschall, Roland ; Kumar, Vipin ; Einert, Marcus:
Effect of sputter-coated platinum on the photostability of nanoporous sol–gel CuO thin film photocathodes.
In: Nanoscale Advances. Bd. 8 (2026) . - S. 4159-4174.
ISSN 2516-0230
DOI: https://doi.org/10.1039/d6na00111d

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Abstract

Copper oxide-based materials are promising candidates as photocathodes for photoelectrochemical (PEC) hydrogen production due to their suitable band gap energy for visible light absorption and appropriate band edge positions for driving the hydrogen evolution reaction. However, the application of CuO suffers from inherent drawbacks, such as poor photostability upon illumination, caused by the position of the Cu2+ reduction potential within the energy band gap of CuO. To protect CuO from photocorrosion, Pt was sputter-coated on nanoporous sol–gel-based CuO thin films prepared by dip-coating using Pluronic® F-127 as a structure-directing agent and, for the first time, citric acid as a complexing agent. Electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy collectively confirmed that Pt can be homogeneously deposited with controlled thicknesses on the nanoporous CuO surface, possessing pore dimensions between 10 nm and 100 nm. The impact of the Pt coating thickness on the PEC performance and stability of CuO was investigated in a neutral aqueous electrolyte. PEC analysis showed that Pt can act as a protective layer, which was indeed found to slow down the photodegradation process of CuO substantially (57% versus 2.9% of the initial photocurrent retained after 30 min of PEC operation). However, Pt coating did not increase gas evolution under irradiation and applied potential, when compared to pristine CuO. The optimum Pt layer thickness in terms of photostability was found to be approximately 20 nm. The empirically derived optoelectronic properties of CuO thin film photocathodes (indirect optical Egap = 1.5 eV) were supported by density functional theory calculations, providing fundamental insight into the electronic band structure. The outcomes of this study demonstrate a reproducible and up-scalable synthetic approach to increase the photostability of CuO-based materials under operating conditions in PEC cells.