Surface Sulfate Oxyanion Enriched Amorphous N‐NiS x Nanostructure for High‐Efficient Methanol Oxidation

ABSTRACT Constructing surface anionic groups on amorphous nanostructure provides a great approach to design highly‐efficient electrocatalysts for electro‐oxidation. In this work, a novel surface modification strategy that the functional sulfate oxyanion (SO 4 2− ) groups are in situ constructed on the surface of amorphous nnitrogen‐doped nickel sulfide (N‐NiS x ‐SO 4 2− ) is proposed to boost the electrocatalytic performance for the representative methanol oxidation reaction (MOR). The SO 4 2− oxyanion is capable of regulating the electronic structure owing to the efficient electron transfer between the SO 4 2− and N‐NiS x , and thus upshifting the Ni d‐band center toward the Fermi level. Impressively, the engineered N‐NiS x ‐SO 4 2− /CNTs electrocatalyst displays lowered anodic oxidation potentials of 1.38 V (vs RHE) at 10 mA cm −2 and excellent long‐term stability over 110 h with negligible degradation, much exceeding the its counterparts. Moreover, the fabricated HER||MOR electrolyzer with N‐NiS x ‐SO 4 2− /CNTs electrocatalyst only requires 1.39 V to reach 10 mA cm −2 and retaining 96.5% of its initial activity after 60 h, outperforming the noble metal‐based benchmarks and the conventional HER||OER setup. The in‐depth theoretical calculation corroborates that the energy barrier for the MOR rate‐determining step ( * CH 3 OH → * CH 3 O) is significantly decreased from 1.16 to 0.64 eV on the N‐NiS x ‐SO 4 2− electrocatalyst owing to its remarkably accelerated electrocatalytic kinetics.