Copper-on-nitride enhances the stable electrosynthesis of multi-carbon products from CO₂

Copper-based materials are promising electrocatalysts for CO₂ reduction. Prior studies show that the mixture of copper (I) and copper (0) at the catalyst surface enhances multi-carbon products from CO₂ reduction; however, the stable presence of copper (I) remains the subject of debate. Here we report a copper on copper (I) composite that stabilizes copper (I) during CO₂ reduction through the use of copper nitride as an underlying copper (I) species. We synthesize a copper-on-nitride catalyst that exhibits a Faradaic efficiency of 64 ± 2% for C₂₊ products. We achieve a 40-fold enhancement in the ratio of C₂₊ to the competing CH₄ compared to the case of pure copper. We further show that the copper-on-nitride catalyst performs stable CO₂ reduction over 30 h. Mechanistic studies suggest that the use of copper nitride contributes to reducing the CO dimerization energy barrier—a rate-limiting step in CO₂ reduction to multi-carbon products.