Copper tantalate by a Sodium-driven flux-mediated synthesis for photoelectrochemical CO2 reduction

Abstract

Copper-tantalate, Cu2Ta4O11 (CTO), shows significant promise as an efficient photocathode for multi-carbon compounds (C2+) production through photoelectrochemical (PEC) CO2 reduction, owing to its suitable energy bands and catalytic surface. However, synthesizing CTO poses a significant challenge due to its metastable nature and thermal instability. In this study, we address this challenge by employing a flux-mediated synthesis technique using a sodium-based flux to create sodium-doped CTO (Na-CTO) thin films, providing enhanced nucleation and stabilization for the CTO phase. To evaluate the PEC performance and catalytic properties of the films, we selectively etched copper(II) oxide (CuO) at the Na-CTO surface. The etched Na-CTO showed a lower dark current, with decreased contribution from photocorrosion, unlike the non-etched Na-CTO which had remaining CuO on the surface. Furthermore, Na-CTO exhibited 7.3-fold ethylene selectivity over hydrogen, thus highlighting its promising potential as a photocathode for C2+ production through PEC CO2 reduction.