First principles investigation on cobalt–tetracyanoquinodimethane monolayer for efficient Bi-functional single atom electrocatalyst

Abstract

A bi-functional electrocatalyst is a stable and catalytically active material for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), the development of which is highly challenging, although essential for application in fuel cells. Herein, the first principle based density functional theory (DFT) computations have been carried out to investigate a series of transition metal-tetracyanoquinodimethane (TM-TCNQ: TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd) monolayer for bi-functional single atom electrocatalyst towards ORR and OER. Amongst various first transition metal row based TCNQ substrates, Cobalt-TCNQ (Co-TCNQ) monolayer was predicted to exhibit best bi-functional catalytic activity. At equilibrium potential (1.23 V, vs RHE), the free energy portraits of Co-TCNQ monolayer for OER in acidic or alkaline media are not completely downhill, measuring an excess potential of 0.6 V, equal to the overpotential, which is needed to be supplied externally to promote the OER activity. On the other hand, an onset potentials of 0.34 V (vs RHE) in acidic media are measured for ORR to proceed. The promising catalytic activity of two dimensional Co-TCNQ monolayer towards ORR and OER as revealed by DFT investigations has been explained in terms of density of states and Bader charge analysis.