Towards superior CORR catalysts: Deciphering the selectivity puzzle over dual-atom catalyst.

The electrocatalytic CO reduction reaction (CORR) is one of the most important electrocatalytic reactions. Starting from a well-defined *CO intermediate, the CORR can bifurcate into two pathways, either forming a hydrogenation product by *CO bond hydrogenation or leading to CO desorption by *C bond cleavage. However, it is perplexing why many dual-atom catalysts (DACs) exhibit high CO selectivity in experiments, despite previous theoretical studies arguing that the CO bond hydrogenation is thermodynamically more favorable than the C bond breaking. Furthermore, the selectivity is contingent upon the potential and is perturbed by the hydrogen evolution reaction (HER), which is far from clear. Using ab initio molecular dynamics and a "slow-growth" sampling method to evaluate the potential-dependent kinetics, we uncover the selectivity origin of CORR to CO on a typical NC-based DAC (CuFe-N-C). Importantly, the results show that at higher CO coverage, CO desorption kinetics are accelerated, while the competing CO bond hydrogenation reaction is inhibited at varying potentials. Furthermore, the selectivity of the HER is observed to increase as the potential decreases. However, at higher CO coverage, the energy barrier for the *C bond cleavage is lower than that for HER, suggesting that HER is suppressed on CuFe-N-C. Our work unlocks a long-standing puzzle about the selectivity of important DAC catalysts for CORR and provides insights for more effective catalyst design.