Boron-Doped Graphene As Active Electrocatalyst For Oxygen Reduction Reaction At A Fuel-Cell Cathode

TL;DR

This study uses DFT calculations to analyze boron-doped graphene as an electrocatalyst for oxygen reduction, revealing favorable associative pathways and pH-dependent stability, aligning well with experimental data.

Contribution

It provides a detailed theoretical analysis of the ORR mechanism on boron-doped graphene, including free energy profiles and pH effects, which was not previously explored.

Findings

Associative pathway is favored over dissociative.

Onset potential at pH 14 is 0.05 V, matching experiments.

Boron doping enhances catalytic activity for ORR.

Abstract

Boron-doped graphene was reported to be the best non-metal doped graphene electrocatalyst for the oxygen reduction reaction (ORR) working at an onset potential of 0.035 V [JACS 136 (2014) 4394]. In the present DFT study, intermediates and transition structures along the possible reaction pathways are determined. Both Langmuir-Hinschelwood and Eley-Rideal mechanisms are discussed. Molecular oxygen binds the positively charged B atom and forms an open shell end-on dioxygen intermediate. The associative path is favoured with respect to the dissociative one. The free energy diagrams along the four-reduction steps are investigated with the methodology by N{\o}rskov and co. [JPC B 108 (2004) 17886] in both acidic and alkaline conditions. The pH effect on the stability of the intermediates of reduction is analyzed in terms of the Pourbaix diagram. At pH = 14 we compute an onset potential value for the electrochemical ORR of U = 0.05 V, which compares very well with the experimental value in alkaline conditions.