Regulating Water Reduction Kinetics on MoP Electrocatalysts Through Se Doping for Accelerated Alkaline Hydrogen Production.

Zhenpeng Liu,Bin Yang,Jian Zhang,Hong Zhong,Wenxiu Ma,Jun Bu,Shuangming Li,Lei Zhang

doi:10.3389/fchem.2021.737495

Abstract

Owing to its low cost, high conductivity, and chemical stability, Molybdenum phosphide (MoP) has great potential for electrochemically catalyzing the hydrogen evolution reaction (HER). Unfortunately, the development of high-activity MoP still remains a grand challenge in alkali-electrolyzers due to its sluggish water reduction kinetics. Here, we demonstrate a novel strategy for regulating the HER kinetics of the MoP nanowire cathode through partially substituting P atoms with Se dopants. In alkaline solutions, the Se-doped MoP (Se-MoP) nanowire cathode exhibits excellent HER performance with a greatly-decreased overpotential of ∼61 mV at 10 mA cm−2 and a Tafel slope of ∼63 mV dec−1, outperforming currently reported MoP-based electrocatalysts. Experimental and theoretical investigations reveal that Se doping not only facilitates the water dissociation on MoP, but also optimize the hydrogen adsorption free energy, eventually speeding up the sluggish alkaline HER kinetics. Therefore, this work paves a new path for designing MoP-based electrocatalyst with high HER performance in alkaline electrolyzers.

Highlights

Because of its large energy density and zero carbon emission, hydrogen (H2) has been proposed as the most promising energy carrier for meeting future energy demands (Turner, 2004; Chu and Majumdar, 2012; Chu et al, 2017)
We develop a phosphorization-selenization process to synthesize Se-doped Molybdenum phosphide (MoP) nanowires consisting of nanoparticles using ultralong Mo nanowires as the Mo source
The microstructures of MoP and Se-doped MoP (Se-MoP) nanowire electrocatalysts were evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Summary

Introduction

Because of its large energy density and zero carbon emission, hydrogen (H2) has been proposed as the most promising energy carrier for meeting future energy demands (Turner, 2004; Chu and Majumdar, 2012; Chu et al, 2017). The Se-MoP nanowires were assembled into a self-supported cathode and performed an excellent HER activity with a low overpotential of ∼61 mV at 10 mA cm−2 and a small Tafel slope of ∼63 mV dec−1 in 1 M KOH solution, which were superior than pure MoP and previously reported MoP-based electrocatalysts.

Results

Conclusion