Atomically ordered PdCu electrocatalysts for selective and stable electrochemical nitrate reduction

Electrochemical nitrate reduction (NO3RR) has attracted attention as an emerging approach to mitigate nitrate pollution in groundwater. Here, we report that a highly ordered PdCu alloy-based electrocatalyst exhibits selective (91% N2), stable (480 hours), and near complete (94%) removal of nitrate without loss of catalyst. In situ and ex situ XAS provide evidence that structural ordering between Pd and Cu improves long-term catalyst stability during NO3RR. In contrast, we also report that a disordered PdCu alloy-based electrocatalyst exhibits non-selective (49% N2 and 49% NH4+), unstable, and incomplete removal of nitrate. The copper within disordered PdCu alloys is vulnerable to accepting electrons from hydrogenated neighboring Pd atoms. This resulted in copper catalyst losses which were 10x greater than that of the ordered catalyst. The design of stable catalysts is imperative for water treatment because loss of the catalyst adds to the system cost and environmental impacts.