Low-cost single-atom transition metals on two-dimensional SnO nanosheets for efficient hydrogen evolution catalysis in all pH-range

The exploration of electrocatalysts with high performance of hydrogen evolution reaction (HER) in all media is essential for developing clean energies. Single-atom catalysts (SACs) have attracted wide attentions owing to their maximum atom utilization and excellent catalytic activity. In this work, the HER activities of transition metal (TM) (TM = Fe, Co, Ni and Cu) SACs on two-dimensional SnO monolayer are studied using density functional theory. We found that the low-cost TM SACs can exhibit high HER activity in wide pH-range. Especially, Co SACs show promising catalytic activity with the Gibbs free energy of hydrogen adsorption (Delta G(H*)) as low as similar to 0.015 eV, which are also high active in either acidic or alkaline environments. With the experimentally inevitable oxygen vacancies in SnO, the Delta G(H*) of Co, Ni and Cu SACs are almost zero, which are competitive with the precious catalyst Pt(111) (-0.09 eV). The exceptional HER activity is correlated to the enhanced electron states close to the Fermi level as well as the d-band center positions of the TM. Our work opens new avenues for engineering low-cost TM SACs with pH-universal HER performance, which is of great importance in practical applications.