Copper Tantalate by a Sodium-Driven Flux-Mediated Synthesis for Photoelectrochemical CO2 Reduction.

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, this challenge is addressed 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, copper(II) oxide (CuO) at the Na-CTO surface is selectively etched. The etched Na-CTO shows a lower dark current, with decreased contribution from photocorrosion, unlike the non-etched Na-CTO which has remaining CuO on the surface. Furthermore, Na-CTO exhibits 7.3-fold ethylene selectivity over hydrogen, thus highlighting its promising potential as a photocathode for C2+ production through PEC CO2 reduction.