Single transition metal atoms anchored on a C2N monolayer as efficient catalysts for hydrazine electrooxidation.

Abstract

Searching for highly-efficient and low-cost electrocatalysts for the hydrazine oxidation reaction (HzOR) is a key issue in the development of direct hydrazine fuel cells for hydrogen production, which is a promising energy-efficient conversion technology to replace the sluggish oxygen evolution reaction in water splitting. Herein, the potential of a series of single transition metal atoms anchored on nitrogenated holey graphene (TM@C2N, TM = Ti, Mn, Fe, Co, Ni, Cu, Mo, Rh, Ru, Pd, Pt, Au, Ag, and W) as catalysts for the HzOR was systematically explored by means of comprehensive density functional theory (DFT) computations. Our results revealed that these TM atoms anchored on a C2N monolayer exhibit high stability due to their strong interactions with the N atoms on the C2N monolayer. Furthermore, on the basis of the computed free energy profiles, Ru@C2N, Mo@C2N, Ti@C2N, Co@C2N, and Fe@C2N were shown to display high HzOR catalytic activity due to their lower (or comparable) limiting potential compared to the well-established Fe-doped CoS2 nanosheet. In particular, Ru@C2N is identified as the best catalyst with the lowest limiting potential of -0.24 V due to its optimum difference between the adsorption strength of N2H3* and N2H2* species. More interestingly, we found that single Mo and Ti atoms also exhibit excellent catalytic performance for the hydrogen evolution reaction, suggesting their bifunctional activity towards hydrazine splitting for H2 production. Our findings provide a new avenue to develop an efficient single-atom electrocatalyst for experimental validation to convert hydrazine into hydrogen.