Understanding alkaline hydrogen evolution promoted by mesopores in three-dimensional graphene-like materials from perspective of capacitance effects

Abstract

The development of simple methods for preparing three-dimensional (3D) mesopore graphene, as well as a comprehension of the connection between pore structure and catalytic characteristics, are critical for building highly efficient Pt-based electrocatalysts, but still challenging. Herein, 3D graphene-like materials with varying mesopore ratios were synthesized from coconut shells using a simple pyrolysis-activation process. It was found that the capacitance effect of 3D graphene-like material (HMG) with high mesopore ratios may facilitate hydrated cation ([K(H2O)m]+) transport and avoid cation (K+) aggregation, hence accelerating the alkaline hydrogen evolution kinetics. As a result, 20 wt% Pt/HMG catalyst outperforms commercial 40 wt% Pt/C catalyst (32 mV) with small overpotentials of 19 mV at 10 mA cm−1 and exhibits a low Tafel slope (43.7 mV·dec−1). This work demonstrates a novel pathway for producing 3D mesopore graphene-like materials for Pt-based supports, as well as the critical role of K+ aggregation and transportation caused by the capacitance effect in alkaline hydrogen evolution.