Awakening (220) as One More Active Facet of PtMo Alloy via Single-Atom Doping to Boost Ammonia Electrooxidation in Direct Ammonia Fuel Cell

As the core of low-temperature direct ammonia fuel cell (DAFC) technology, electrocatalytic ammonia oxidation reaction (AOR) has proven to be most active on platinum-based catalysts. However, the AOR is extremely surface sensitive that only the Pt (200) facet exhibits high reaction activity, whereas other facets usually do not make contributions. Herein, the inert (220) surface of PtMo nano-alloy is successfully awakened as one more active facet in addition to (200) via directional single-atom Ni-doping. The introduction of Ni triggers a targeted electron accumulation around Pt sites at the (220) facet that significantly reduces the AOR energy barrier while maintaining the activity of the (200) surface. With a greatly enlarged active surface, the Ni-decorated PtMo catalyst exhibits a significantly facilitated AOR kinetics with a low onset potential of 0.49 V versus reversible hydrogen electrode and a superior peak current density of 94.96 A g(-1) at 5 mV s(-1). Notably, the DAFC equipped with such an electrocatalyst reaches a remarkable peak power density of 16.70 mW cm(-2) at low temperatures. It is believed that this strategy sheds light on exploiting the intrinsic activity of Pt-based electrocatalysts, and drives the low-temperature DAFC technology to a more practical level.

Automated summary

By introducing single-atom Ni-doping, the inert (220) surface of PtMo nano-alloy is activated as an additional active facet in addition to (200). The Ni triggers electron accumulation around Pt sites at the (220) facet, reducing the energy barrier for electrocatalytic ammonia oxidation reaction (AOR) and maintaining the activity of the (200) surface. The Ni-decorated PtMo catalyst exhibits significantly improved AOR kinetics and the DAFC equipped with this catalyst achieves a remarkable peak power density of 16.70 mW cm(-2) at low temperatures.