Atomically Ordered PdCu Electrocatalysts for Selective and Stable Electrochemical Nitrate Reduction.

Electrochemical nitrate reduction (NO 3 RR) 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% N 2 ), stable (480 h), 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 NO 3 RR. In contrast, we also report that a disordered PdCu alloy-based electrocatalyst exhibits non-selective (44% N 2 and 49% NH 4 + ), unstable, and incomplete removal of nitrate. The copper within disordered PdCu alloy is vulnerable to accepting electrons from hydrogenated neighboring Pd atoms. This resulted in copper catalyst losses which were 10× 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.