Self-standing hollow Ni-doped Mo2C nanotube arrays induced by the Kirkendall effect for an efficient hydrogen evolution reaction in acidic and alkaline solutions

Abstract

The development of efficient nonprecious catalysts for the hydrogen evolution reaction (HER) in water electrolysis is highly desirable but challenging. Molybdenum carbides, as a promising candidate, show excellent catalytic activity in both acidic and alkaline solutions. In this work, we report a self-supporting hollow Ni-doped Mo₂C nanotube array with varying Ni concentrations. Specifically, a thin layer of Ni and C composites was deposited on the surface of MoO₃ by plasma-enhanced chemical vapor deposition (PECVD), and in the subsequent carbonization process, a hollow structure was formed due to the Kirkendall effect, which endows the obtained electrode with a high specific surface area and a superior superhydrophilic/superaerophobic surface. In addition, the incorporation of Ni into Mo₂C could weaken the H* adsorption and thus improve the HER catalytic activity, as confirmed by density functional theory calculations. As a result, the as-prepared Ni-doped hollow Mo₂C hexagonal prism arrays are endowed with high catalytic activity in both acidic and alkaline solutions, 93 mV in 1 M KOH and 122 mV in 0.5 M H₂SO₄ to drive 10 mA cm⁻². Our work may provide a new way to enhance the performance of nonprecious electrocatalysts for the HER.