Size-Dependent Nickel-Based Electrocatalysts for Selective CO Reduction.

Closing the anthropogenic carbon cycle by converting CO into reusable chemicals is an attractive solution to mitigate rising concentrations of CO 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 which were obtained from converted zeolitic imidazolate frameworks (ZIF). The results show variance in CO reduction performance with variance in Ni metal size. Ni single atoms demonstrate a superior Faradaic efficiency (FE) for CO selectivity (ca. 97 % at -0.8 V vs. RHE), while results for 4.1 nm Ni nanoparticles are slightly lower (ca. 93 %). Further increase the Ni particle size to 37.2 nm allows the H evolution reaction (HER) to compete with the CO reduction reaction (CO RR). The FE towards CO production decreases to under 30 % and HER efficiency increase to over 70 %. These results show a size-dependent CO reduction for various sizes of Ni metal catalysts.