In situ self-assembled bismuth oxide fractals enabling highly selective electrosynthesis of formate in flow cells at high current densities

In this work, we present a scalable in-situ growth strategy for self-assembling a carbon felt supported Bi 2 O 3 fractal nanostructure (f-Bi 2 O 3 /CF), enabling superior performance towards electrocatalytic CO 2 -to-formate conversion with an optimal Faradaic efficiency of 95.1% at −0.9 V ( vs . RHE) in flow cell. More impressively, the current density reaches an industrially relevant 235.7 mA cm −2 and remains a high FE formate of 87.7%. The enhanced catalytic activity of the f-Bi 2 O 3 /CF model is attributed to the increased adsorption energy of OCHO* intermediate by changing the surface charge distribution according to DFT calculations. Using the aforementioned method, a series of other CF supported metal oxide catalysts (i.e., CuO , In 2 O 3 , and SnO 2 ) are easily obtained. A brief techno-economic analysis (TEA) model demonstrates the economic potential of electrocatalytic hydrogenation of CO 2 into formate in flow cell. Our findings offer a promising pathway for the fabrication of stable and accessible fractal structure, applicable to a wide range of scenarios.