MoNi4–NiO heterojunction encapsulated in lignin-derived carbon for efficient hydrogen evolution reaction

Abstract

Molybdenum nickel alloy has been proved to be an efficient noble-metal-free catalyst for hydrogen evolution reaction (HER) in alkaline medium, but its electrocatalytic activity and stability need to be further improved to meet industrial requirements. In this study, carboxymethylated enzymatic hydrolysis lignin (EHL) was used as a biomacromolecule frame to coordinate with transition metal ions and reduced by pyrolysis to obtain the MoNi4–NiO heterojunction (MoNi4–NiO/C). The oblate sphere structure of MoNi4–NiO/C exposed a large catalytic active surface to the electrolyte. As a result, the hydrogen evolution reaction of MoNi4–NiO/C displayed a low overpotentials of 41 mV to achieve 10 mA cm−2 and excellent stability of 100 h at 100 mA cm−2 in 1 mol L−1 KOH, which was superior to that of commercial Pt/C. Lignin assisted the formation of NiO to construct the MoNi4–NiO interface and MoNi4–NiO heterojunction structure, which reduced the energy barrier by forming a more favorable transition states and then promoted the formation of adsorbed hydrogen at the heterojunction interface through water dissociation in alkaline media, leading to the rapid reaction kinetics. This work provided an effective strategy for improving the electrocatalytic performance of noble-metal-free electrocatalysts encapsulated by lignin-derived carbon.

Keywords

• Lignin-derived carbon
• Hydrogen evolution reaction
• MoNi4–NiO interface
• Electrocatalysis