Self‐Supported Hierarchical Shell@Core Ni3S2@Ni Foam Composite Electrocatalyst with High Efficiency and Long‐Term Stability for Methanol Oxidation.

Abstract: Direct methanol fuel cells are promising renewable energy devices for automobiles and portable electronic devices. The development of high effciency, poison tolerance, long‐term stability, and noble metal‐free electrocatalysts for methanol oxidation is still a major challenge. Herein, we develop a noble metal‐free, 3D self‐supported, defect‐rich, hierarchical shell‐core structured Ni₃S₂ composite on Ni foam as electrocatalyst. This electrocatalyst shows a good activity, poison tolerance, and long‐term durability towards methanol oxidation in alkaline media. It shows the lowest onset potential (−340 mV vs. Hg/HgO) among all the Ni‐based catalysts reported up to date and a Pt‐level specific activity. The methanol oxidation peak current of the electrocatalyst retains more than 97.5 % even after 5,000 voltammetry cycles in 0.5 M KOH+1 M CH₃OH. The morphology and composition of the electrocatalysts before and after stability test were characterized by SEM, TEM, XRD, and XPS. The high activity, poison tolerance, and stability are attributed to the binder‐free, directly grown Ni₃S₂ shell on the Ni foam backbone, the lattice defect sites, and the synergetic effects between the in‐situ formed active NiO_x core and Ni₃S₂ shell during methanol oxidation. This work indicates that the self‐supported hierarchical shell‐core Ni₃S₂@Ni foam electrocatalyst is a viable alternative for commercial Pt‐based electrocatalyst applied in fuel cells. [ABSTRACT FROM AUTHOR]