In Operando Spectroscopic Study for Durable Ammonia Electrolysis on Platinum

Abstract

Ammonia has recently been considered as a promising energy carrier and a carbon-free fuel. Combining with renewable energy sources, ammonia oxidation reaction (AOR) is crucial reaction for onsite hydrogen-fuel production and electricity generation in future energy scenario. In spite of promising beginning-of-life AOR activity of platinum, its implementation is hampered by vulnerable AOR catalysis. Hence, improved durability is critically needed but challenged by insufficient understanding of its degradation mechanism during NH3 electrolysis. In this work, we study the degradation mechanisms of Pt during AOR catalysis with operando and in/ex situ spectroscopies. Passivation of the Pt surface and complexation of the dissolved Pt ions by NH3 (or NH3 derivatives during AOR) are identified. Such chemical modifications accelerate Pt dissolution by forming stable complex while decelerate Pt redeposition by passivation of Pt surface, which lead to the instable nature of Pt electrocatalysis toward AOR. Based on the potential-resolved investigations, a stable operando potential window and strategy for operating AOR are suggested in this study. The preliminary AOR protocol demonstrates prolonged NH3 electrolysis without significant degradation of Pt, which implicates the possible usage of NH3 as an energy carrier when the proposed operation strategy is further developed.