Rh@C8N8 monolayer as a promising single-atom-catalyst for overall water splitting

Rh@C8N8 monolayer is a promising single-atom-catalyst for overall water splitting due to its HER and OER with hydrogen adsorption free energy (ΔGH*)/ over-potential (η) of 0.08 eV/0.49 V at pH=7. [Display omitted] •The TM@C8N8 monolayers are constructed by embedded TM atoms in periodic C8N8 cell based on poly(pyrazine-2,3-diamine) units.•Rh@C8N8 monolayer is screened out from 15 TM@C8N8 monolayers to be a promising single-atom-catalyst for overall water splitting.•Rh@C8N8 exhibits superior catalytic activity toward HER and OER with hydrogen adsorption free energy (ΔGH*)/over-potential (η) of 0.08 eV/0.49 V at pH=7.•Rh@C8N8 possesses excellent stability at high temperatures (1000 K). Development of efficient single-atom-catalysts (SACs) is a promising strategy for electrochemical water splitting. High over-potential and poor stability of catalysts remain to be challenges for overall water splitting. In this work, through the first-principles calculations, we screen a novel series of TM@C8N8 monolayers, constructed by embedding transition metal atoms in our proposed C8N8 monolayer based on poly(pyrazine-2,3-diamine) units using the kinetic stability and the projected density of states. Their catalytic performance of intrinsic TM-N4 moiety is investigated for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) using the Gibbs free energy change (ΔG) of each elementary step. Especially, Rh@C8N8 exhibits superior catalytic activity toward HER and OER with hydrogen adsorption free energy (ΔGH*)/over-potential (η) of 0.08 eV/0.49 V at pH = 7. In addition, it is unbroken at high temperatures (1000 K) using the first-principle molecular dynamics simulation. Therefore, Rh@C8N8 monolayer can perform as an efficient bifunctional catalyst for overall water splitting. It is also expected that our results can serve as the theoretical basis to open the door for future experimental research on novel CN layered-materials containing TM-N4 moiety.