Single-atom transition metals supported on defective graphene for electrochemical reduction of acetonitrile to ethylamine

The electrochemical acetonitrile (CH3CN) reduction reaction provides an alternative to produce ethylamine (CH3CH2NH2) under ambient conditions but remains challenging. Using density functional theory (DFT) calculations, we explored the catalytic performance of four types of graphene-based single-atom catalysts (SACs) total of 32 materials toward the CH3CN reduction reaction. We identified that two highly stable SACs, namely Cr@N4 and Mn@N4, can greatly accelerate both reaction thermodynamics and kinetics with small energy barriers. In particular, these two SACs can effectively suppress the competitive hydrogen evolution reaction (HER) by selective adsorption of key intermediate of *CH3CN rather than *H, which feature superior catalytic selectivity. More impressively, the activity trends of various candidates can be directly correlated to the adsorption energy of *CH3CHN (delta E(*CH3CHN)), and the underlying activity origin is ascribed by the enhancement of the adsorption for the *CH3CHN. Furthermore, detailed electronic property analyses indicate that the bonding/anti-bonding interactions of different active metal centers with *CH3CHN are the key factor determining the adsorption strength. The more bonding contributions below the Fermi level (E-f) lead to the stronger *CH3CHN combination on active metal centers, while the anti-bonding state is opposite. As a result, Cr@N-4 stands out among these candidates, which can tune the performance of acetonitrile reduction reaction by balancing the reactivity of CH3CN and the desorption of CH3CH2NH2. Our results unveil that the excellent catalytic activity of Cr@N-4 for CH3CN reduction reaction can be further confirmed by calculating the bond lengths and charge variations. With the elongation of C Xi N bond in the adsorbed CH3CHxNHy, CH3CN molecule can be effectively activated on Cr@N-4. Overall, this work addresses a promising active catalyst and will be of a guidance of great theoretical significance to construct carbon-based materials supported transition metal single-atom electro-catalysts for the CH3CN reduction reaction.