Ni2P enhances the activity and durability of the Pt anode catalyst in direct methanol fuel cells

Abstract

Pt is the state-of-the-art anode catalyst in direct methanol fuel cells. Here we report that Ni₂P promotes the activity and stability of Pt in electrochemical methanol oxidation. Nanoparticles of Ni₂P and Pt were co-deposited on a carbon support and their activity in electrochemical methanol oxidation was measured by cyclic voltammetry. Among all Pt–Ni₂P/C catalysts, the sample with a 30 wt% loading of Ni₂P exhibits the highest electrochemical surface area and activity. The activity of the Pt–Ni₂P/C-30% catalyst is significantly higher than that of Pt/C, Ni-promoted Pt/C, and P-promoted Pt/C catalysts, revealed by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Accordingly to X-ray photoelectron spectroscopy, there is a partial electron transfer from Ni₂P to Pt, which might be an origin of the enhanced catalytic activity of the Pt/Ni₂P bimetallic catalyst. The Pt–Ni₂P/C-30% was integrated into a direct methanol fuel cell; this fuel cell exhibits a maximum power density of 65 mW cm⁻², more than twice of that of an analogous fuel cell using Pt/C as the anode catalyst. The Pt–Ni₂P/C-30%-integrated direct methanol fuel cell has also the highest discharge stability among a series of fuel cells with different Pt-based anode catalysts.