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Converting hydrogen chemical energy into electrical energy by fuel cells offers high efficiencies and environmental advantages, but ultrapure hydrogen (over 99.97%) is required; otherwise, the electrode catalysts, typically platinum on carbon (Pt/C), will be poisoned by impurity gases such as ammonia (NH 3 ). Here we demonstrate remarkable NH 3 resistivity over a nickel–molybdenum alloy (MoNi 4 ) modulated by chromium (Cr) dopants. The resultant Cr-MoNi 4 exhibits high activity toward alkaline hydrogen oxidation and can undergo 10,000 cycles without apparent activity decay in the presence of 2 ppm of NH 3 . Furthermore, a fuel cell assembled with this catalyst retains 95% of the initial peak power density even when NH 3 (10 ppm)/H 2 was fed, whereas the power output reduces to 61% of the initial value for the Pt/C catalyst. Experimental and theoretical studies reveal that the Cr modifier not only creates electron-rich states that restrain lone-pair electron donation but also downshifts the d-band center to suppress d-electron back-donation, synergistically weakening NH 3 adsorption.
Wang et al. (Tue,) studied this question.