High-valence metal doped Co2FeAl alloy as efficient noble-metal-free electrocatalyst for alkaline hydrogen evolution reaction

Abstract

Most efficient electrochemical hydrogen evolution reaction (HER) catalysts in alkaline solutions are based on precious metals, whose rarity and high cost are severely limiting their large-scale applications. In this work, we synthesized Mo-doped and W-doped Co2FeAl alloys by a simple coprecipitation method. The HER in alkaline solution is promoted through the synergistic effect of thermal annealing and doping of high-valence metal atoms. Thermal annealing could optimize the surface morphology and improve the crystallinity. In the meantime, the doping of high-valence metal atoms could further regulate the crystal structure and electronic structure of alloys. Therefore, annealing temperatures and doping concentrations have a marked impact on the catalytic performance. In particular, when the Mo doping concentration is 27 at% and the annealing temperature is 750 ℃, the synthesized Co2FeAlMo1.5 (750 ℃) alloy electrocatalyst exhibits the superior HER performance in alkaline media. It displays a low overpotential of only 71 mV at 10 mA cm−2 and a Tafel slope of 110 mV dec−1. An excellent stability is also demonstrated that the electrocatalyst can work stably for 20 h and the overpotential is only shifted by 2 mV after 1000 cycles. A series of characterization tests indicate that the crystal structure and electronic structure of Co2FeAlMo1.5 (750 ℃) are optimized, which can improve the catalytic activity and promote alkaline HER. This work provides a new strategy for improving the catalytic performance of non-noble metal electrocatalysts for alkaline HER.