Creating metal-carbide interactions to boost ammonia oxidation activity for low-temperature direct ammonia fuel cells

Abstract

Low-temperature direct ammonia fuel cell (DAFC) can easily transform the chemical energy into green in-commission power, yet remains great challenging due to kinetically sluggish ammonia oxidation reaction (AOR). The interface engineering is a promising strategy to take advantage of synergistic proficiencies and electronic properties, which was widely applied in heterogeneous catalysis but rarely studied in AOR. Herein, non-oxide-based metal–metal carbide interfaces were employed to construct excellent AOR catalysts. The as-built Pt/WC and PtIr/WC catalysts with the excellent peak current densities of 96.5 and 61.7 A gPGM−1, respectively, which are over 3.5-fold and 2.7-fold than those of carbon-supported catalysts. Both experimental and theoretical studies reveal that the charge transfer between PtIr NPs and WC regulates the work function and d-band center of catalysts and further alters adsorption energies of intermediates. The WC also plays an important role for water dissociation and hydroxyl group activation. Based on the understanding, maximizing active interfaces by dispersing PtIr–WC composites onto CNTs (PtIr–WC/CNT) achieves a compelling peak power density of 140.0 mW cm−2 at 80 °C in a DAFC test, which is at the top of previously reported catalysts at similar conditions. Our study provides a way to design highly-active catalysts for AOR and DAFC by interface engineering.