Ni and NiO in situ grown on sulfur and phosphorus co-doped graphene as effective bifunctional catalyst for hydrogen evolution

Abstract

Designing a precious-metal-free catalyst with high activity and stability is of great significance for hydrogen evolution reaction (HER). Herein, sulfur (S) and phosphorus (P) co-doped graphene (SPG) is successfully synthesized via a facile hydrothermal process using sulfuric acid and phytic acid as sulfur and phosphorus dopant. Subsequently, two types of nickel-based nanomaterials grown directly on SPG (abbreviated as Ni/SPG and NiO/SPG) are fabricated through a simple alcohol-thermal method. The as-prepared Ni/SPG electrocatalyst display unexpected HER performance with extremely small impedance (0.48 Ω), wonderful electrochemically active surface areas (32.6 m2/g), high TOF (0.0051 s−1), low initial potential (25 mV), excellent Tafel slope (79 mV decade−1) and more excellent stable cycle stability (5000 cyclic voltammetry cycles). These remarkable electrocatalytic properties are attributed to the S and P dual-doping graphene producing more exposed active sites and surface defects, which allows Ni with small crystallite size uniformly dispersed on its surface and the facilitated electron transport between them.