Size‐dependent Ni‐based electrocatalysts for selective CO2 reduction

Closing the anthropogenic carbon cycle by converting CO 2 into reusable chemicals is recognized as an attractive solution to mitigate rising concentrations of CO 2 in the atmosphere. Herein, we prepared Ni metal catalysts ranging in size from single atoms to over 100 nm and distributed them across N-doped carbon substrates obtained from converted zeolitic imidazolate frameworks (ZIF). Results show variance in CO 2 reduction performance with variance in Ni metal size. Ni single atoms demonstrate a superior Faradaic efficiency (FE) for CO selectivity of ~97% at -0.8 V vs. RHE, while results for 4.1 nm Ni nanoparticles are slightly lower (~93%). Further increase the particle size to 37.2 nm in Ni allows the H 2 evolution reaction (HER) to compete with CO 2 reduction reaction (CO 2 RR), with a FE towards CO production decrease to 70%. These results uncover a size-dependent tendency towards CO 2 reduction for various sizes of Ni metal catalysts. The successful demonstration of metal size effects towards CO 2 RR resulting from this study will not only benefit renewable utilization for CO 2 , but also guide the future design of size-controlled electrocatalysts for efficient conversion of CO 2 into more useful chemicals.