Free-standing multi-hierarchical MoC-based catalyst for pH-universal hydrogen evolution reaction at ultra-high current density

Abstract

An efficient and durable free-standing electrocatalyst is the key to achieving pH-universal hydrogen evolution reaction under ultra-high current density. Herein, the free-standing three-stage concentric shaft structure of MoC@C shell-supported MoC nanoparticles anchored Ni@N-doped carbon nanotube vertical nanoarrays (P-MoC/Ni@NCNTs-MoC@C) are fabricated through a simple spraying and pyrolysis process. The formation of a MoC@C shell facilitates Ni nanoparticles' anchoring, resulting in Ni@N-doped carbon nanotube vertical arrays (Ni@NCNTs). Additionally, the Ni@NCNTs effectively capture the escaped molybdenum vapor, leading to the generation of MoC nanoparticles. The unique structure provides increased catalytic active sites and larger specific surface area, improving charge transfer and the release of bubbles. As such, the free-standing P-MoC/Ni@NCNTs-MoC@C catalyst exhibits lower overpotentials compared to previously reported articles, with values of 238.1 mV in 1.0 M KOH (1800 mA cm⁻²), 250.2 mV in 0.5 M H₂SO₄ (1800 mA cm⁻²), and 567.9 mV in 1.0 M PBS (1000 mA cm⁻²). Additionally, it represents low Tafel slopes of 71.1 mV dec⁻¹, 67.4 mV dec⁻¹, and 130.3 mV dec⁻¹ in alkaline, acidic, and neutral condition, respectively. The current work may provide insight into the rational design of free-standing catalysts for practical applications.