Improving the Antioxidation Capability of the Ni Catalyst by Carbon Shell Coating for Alkaline Hydrogen Oxidation Reaction.

Increasing the antioxidation capability of Ni for the hydrogen oxidation reaction (HOR) is considered important and challenging for alkaline polymer electrolyte fuel cells (APEFCs). Herein, we report a series of Ni-core carbon-shell (Ni@C) catalysts obtained by a vacuum pyrolysis method treated at different temperatures. According to the cyclic voltammetry tests and the HOR tests, Ni@C treated at 500 °C exhibits a much higher Ni core utilization and better catalytic activity toward HOR than the commonly used Ni/C catalyst. Furthermore, X-ray photoelectron spectroscopy characterization shows that a higher percentage of Ni0 appears at the surface of the Ni core of Ni@C than the Ni/C catalyst. The accelerated durability tests, as well as the chronoamperometry tests, suggest that the antioxidation capability of Ni has been obviously improved by the carbon shells. The Raman spectra show that the graphitization degree of the carbon shells might be the key factor affecting the Ni utilization and the HOR catalytic activity of the Ni@C catalysts. The APEFC achieves a peak power density of 160 mW/cm2 using Ni@C-500 °C as the anode, which could also stably discharge for 120 h at 0.7 V.