Abstract
Single transition metal (TM) atoms such as Fe, Co and Ni occupying a carbon divacancy in tetragonal graphene (TG) and bonded with four nitrogen atoms (TM@N(4) TG) as electrocatalysts are investigated by means of first-principles calculations. To consider the effect of solvent species on the local configuration of the active single metal, a thermodynamical full-landscape searching (TFLS) scheme is employed. The calculated thermodynamic overpotentials (η(td) ) from our TFLS indicate that Co@N(4) TG displays high catalytic activity toward both oxygen evolution reaction (OER) and reduction reaction (ORR), with η(td) (OER) and η(td) (ORR) as 0.397 and 0.357 V, respectively. Its OER potential cannot be captured if only one four electron reaction loop (FERL) is considered. The actual active pathways do not always turn out to be the reactions starting from the bare site. Our findings demonstrate that TG is a promising support and TM confined TD can be used to design effective and cheap multifunctional electrocatalysts.