Computational exploration of borophane-supported single transition metal atoms as potential oxygen reduction and evolution electrocatalysts

Abstract

Novel monolayer-boron (borophene) is a recent addition to the family of 2D materials. In particular, full surface hydrogenation of triangular borophene (borophane (BH)) to passivate empty p orbitals in boron is identified as producing a new stable 2D material that possesses direction-dependent Dirac cones similar to graphene. By a series of density functional theory (DFT) computations, we investigated the potential of single transition metal atoms supported on borophane with vacancies (the TM-BH system) as an efficient ORR/OER electrocatalyst for applications in renewable energy technologies. In TM-BH systems, the coupling of d-orbitals of the TM dopant with the p-orbitals of surrounding boron atoms results in an increase in the density of states near the Fermi-level generating active sites to facilitate the ORR/OER via an efficient four-electron transfer mechanism. Among the considered TM-BH systems, Fe-BH and Rh-BH were found to be promising ORR electrocatalysts with overpotentials (eta(ORR)) of 0.43 V and 0.47 V, respectively, whereas, for the OER, Rh-BH with 0.24 V has the smallest eta(OER) value followed by Co-BH (0.37 V), under the equilibrium electrode potential. These eta(ORR) and eta(OER) values indicate higher activities than the current most active ORR (Pt(111) (0.63 V)) and OER (rutile-type RuO2 (0.37 V)) electrocatalysts.