Rapid synthesis of interconnected CuCrO2 nanostructures: A promising electrode material for photoelectrochemical fuel generation

Highlights: • Solution combustion synthesis resulted in CuCrO₂ having interconnected nanostructure. • Impressive photocurrent densities were achieved in CO₂ reduction and H₂ evolution. • The formation of H₂, CO, CH₄, CH3OH and HCOOH was confirmed. Solar fuel generation is a promising avenue to mitigate the harmful effects of the increasing carbon dioxide concentration in the atmosphere. Both photoelectrochemical water splitting and carbon dioxide reduction are viable pathways to utilize solar irradiation, however, there is a strong need for novel photoelectrode materials with enhanced properties. Copper-based delafossites (CuMO₂, where M: Cr, Al, Fe, Rh, etc.) are attractive photocathode candidates because their conduction band position lies at a sufficiently negative potential for both carbon dioxide reduction and hydrogen evolution. In this study copper chromium delafossite (CuCrO₂) nanostructures were prepared by solution combustion synthesis; which yielded an almost phase pure, partially crystalline product within five minutes. The nanocrystalline samples were characterized by powder X-ray diffraction, transmission and scanning electron microscopy, UV–vis diffuse reflectance, FT-IR, and Raman spectroscopy. Linear sweep photovoltammograms indicated a promising photoelectrochemical performance (especially after thermal annealing), which is rooted in the interconnected porous structure of the samples. Long-term photoelectrolysis proved that CuCrO₂ can reduce carbon dioxide to carbon monoxide, methane, formic acid, and methanol, while hydrogen was co-generated from water splitting. What is further important, CuCrO₂ was more resistant to photocorrosion (i.e., metallic copper formation) than its monometallic Cu₂O counterpart.