Probing the electronic and geometric structures of photoactive electrodeposited Cu2O films by X-ray absorption spectroscopy

Correlating the Valence State with the Adsorption Behavior of a Cu-Based Electrocatalyst for Furfural Oxidation with Anodic Hydrogen Production Reaction

The low-potential furfural oxidation reaction (FFOR) on a Cu-based electrocatalyst can produce H2 at the anode, thereby providing a bipolar H2 production system with an ultralow cell voltage. However, the intrinsic activity and stability of the Cu-based electrocatalyst for the FFOR remain unsatisfactory for practical applications. This study investigates the correlation between the valence state and the adsorption behavior of the Cu-based electrocatalyst in furfural oxidation. Cu0 is the adsorption site with low intrinsic activity. Cu+ , which exists in the form of Cu(OH)ads in alkaline electrolytes, has no adsorption ability but can improve the performance of Cu0 by promoting the adsorption of FF. Moreover, a mixed-valence Cu-based electrocatalyst (MV Cu) with high intrinsic activity and stability is prepared electrochemically. With the MV Cu catalyst, the assembled dual-side H2 production electrolyzer has a low electricity requirement of only 0.24 kWh mH2 -3 at an ultralow cell voltage of 0.3 V, and it exhibits sufficient stability. This study not only correlates the valence state with the adsorption behavior of the Cu-based electrocatalyst for the low-potential FFOR with anodic H2 production but also reveals the mechanism of deactivation to provide design principles for Cu-based electrocatalysts with satisfactory stability.

Understanding the Role of Copper Vacancies in Photoelectrochemical CO2 Reduction on Cuprous Oxide

Controlling the electronic and photoexcited properties of cuprous oxide (Cu₂O) through slight modifications of the synthesis method can impact a wide range of emerging technologies. Herein, we consider copper vacancies in Cu₂O as a prototype of a p-type oxide semiconductor for studying the impact of crystal and electronic structure on carbon dioxide photoreduction. Oriented films of copper vacancy modulated Cu₂O consisting of nano twin structures are electrodeposited by changing the potential in an aqueous alkaline copper(II)-lactate solution. The copper vacancies introduce tail states inside the band gap, improving the hole concentration and facilitating the charge separation and transfer in the Cu₂O photocathode. This study gives an in-depth view of how a cation-deficient structure regulates and promotes photoelectrochemical activity toward CO₂ reduction.