Halide precursor reduction strategy to modulate bismuthene with high selectivity and wide potential window for electrochemical CO2 reduction

Developing high-performance electrocatalysts for CO 2 reduction reaction (CO 2 RR) is vital in achieving a carbon-neutral society by converting CO 2 into valuable chemicals. CO 2 RR electrocatalyst with lower overpotential, higher selectivity and wider working potential range is urgently desired, but it is still challenging to realize these factors simultaneously. Here, high-performance bismuthene-based electrocatalysts were synthesized by reducing bismuth precursors like BiCl 3 , BiBr 3 , and BiI 3 in liquid phases. Especially, bismuthene-I derived from BiI 3 showed a nanosheet morphology (around four-layer) with significantly enhanced (110) surfaces. It enabled an ultrawide potential window (0.7 V) for high formate selectivity (>90%) in a H-type cell and achieved an ultralow potential (−0.46 V vs. reversible hydrogen electrode) to attain a current density of 200 mA cm −2 in a gas-diffusion flow cell. The prominent long-term operational capability of bismuthene-I was demonstrated in both H-type and gas-diffusion cells. Density functional theory calculations revealed that bismuthene-I possessed abundant topological Bi(110) surfaces states that can reduce the CO 2 RR overpotential, suppress the competitive hydrogen evolution reaction, and facilitate electron donation during CO 2 electrocatalysis. The bismuthene-I realized low overpotential, high selectivity and wide working potential range simultaneously for electrochemical CO 2 RR. This work unfolds the broader plausibility of facilely reducing precursors for the scalable fabrication of high-performing CO 2 RR electrocatalysts.