Electrocatalyst Derived from Waste Cu–Sn Bronze for CO₂ Conversion into CO

To sustainably exist within planetary boundaries, we must greatly curtail our extraction of fuels and materials from the Earth. This requires new technologies based on reuse and repurposing of material already available. Electrochemical conversion of CO₂ into valuable chemicals and fuels is a promising alternative to deriving them from fossil fuels. But most metals used for electrocatalysis are either endangered or at serious risk of limitation to their future supply. Here, we demonstrate a combined strategy for repurposing of a waste industrial Cu-Sn bronze as a catalyst material precursor and its application toward CO₂ reuse. By a simple electrochemical transfer method, waste bronzes with composition Cu₁₄Sn were anodically dissolved and cathodically redeposited under dynamic hydrogen bubble template conditions to yield mesoporous foams with Cu₁₀Sn surface composition. The bimetal foam electrodes exhibited high CO₂ electroreduction selectivity toward CO, achieving greater than 85% faradaic efficiency accompanied by a considerable suppression of the competing H₂ evolution reaction. The Cu-Sn foam electrodes showed good durability over several hours of continuous electrolysis without any significant change in the composition, morphology, and selectivity for CO as a target product.