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

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.