Efficient NH3-Tolerant Nickel-Based Hydrogen Oxidation Catalyst for Anion Exchange Membrane Fuel Cells

Convertinghydrogen chemical energy into electrical energy by fuelcells offers high efficiencies and environmental advantages, but ultrapurehydrogen (over 99.97%) is required; otherwise, the electrode catalysts,typically platinum on carbon (Pt/C), will be poisoned by impuritygases such as ammonia (NH3). Here we demonstrate remarkableNH(3) resistivity over a nickel-molybdenum alloy (MoNi4) modulated by chromium (Cr) dopants. The resultant Cr-MoNi4 exhibits high activity toward alkaline hydrogen oxidationand can undergo 10,000 cycles without apparent activity decay in thepresence of 2 ppm of NH3. Furthermore, a fuel cell assembledwith this catalyst retains 95% of the initial peak power density evenwhen NH3 (10 ppm)/H-2 was fed, whereas the poweroutput reduces to 61% of the initial value for the Pt/C catalyst.Experimental and theoretical studies reveal that the Cr modifier notonly creates electron-rich states that restrain lone-pair electrondonation but also downshifts the d-band center to suppress d-electronback-donation, synergistically weakening NH3 adsorption.