(569cr) Unveiling Alkali-Cation Induced Cathodic Corrosion in Cu Catalysts - a Missing Puzzle Piece for Understanding Their Performance in the Electrochemical Reduction of CO2

The electrochemical reduction reaction of CO2 (CO2RR) to higher-value chemicals presents a promising avenue for addressing climate change and promoting sustainability in the chemical industry. Copper (Cu) electrocatalysts are unique in their ability to produce multi-carbon products with high efficiencies. Despite significant research efforts, the reconstruction of Cu catalysts during electrochemical reduction of CO2 (CO2RR) is a widely known but poorly understood phenomenon.

Investigating the reconstruction of Cu has been challenging due to Cu's susceptibility to oxidation. This work examines the structural evolution of Cu nanocubes under CO2RR conditions using identical location TEM, CV, and other complementary characterization techniques, along with AIMD simulations, uncovering a previously unrecognized mechanism of alkali cation-induced cathodic corrosion. This process, critical under highly cathodic conditions with alkali cations in the electrolyte, results in the etching and redeposition of Cu, leading to the observed reconstruction of Cu catalysts. This finding underscores the inevitability of surface reconstructions and dynamic morphologies in Cu catalysts under CO2RR conditions, challenging the notion that engineered pre-catalyst morphologies can yield long-term benefits in selectivity or activity.

We show that dynamic morphologies need not compromise the stability of Cu catalysts, as equilibrium morphologies may be achievable. However, alkali cation-induced cathodic corrosion makes the strategies for morphology engineering of Cu precatalysts less effective. By operating Cu catalysts at less negative potentials, we show that it is possible to mitigate cathodic corrosion, thereby maintaining a stable selectivity advantage from morphology-controlled Cu nanocubes over spherical Cu particles.

Figure caption: Identical location TEM images of Cu nanocubes before and after CO2RR at -1.1 V_RHE. (b) the product distribution of Cu nanocubes and 25 nm Cu particles in CO2RR at -1.1V_RHE in 0.1M KHCO3 in an H-cell. (c) The stable liquid product distribution from 40 nm Cu nanocubes used in CORR at -0.37 V_RHE in 1M KOH.