Self-Supported Pd Nanorod Arrays for High-Efficient Nitrate Electroreduction to Ammonia.

Electrochemical nitrate (NO 3 - ) reduction to ammonia (NH 3 ) offers a promising pathway to recover NO 3 - pollutants from industrial wastewater that can balance the nitrogen cycle and sustainable green NH 3 production. However, the efficiency of electrocatalytic NO 3 - reduction to NH 3 synthesis remains low for most of electrocatalysts due to complex reaction processes and severe hydrogen precipitation reaction. Herein, high performance of nitrate reduction reaction (NO 3 - RR) is demonstrated on self-supported Pd nanorod arrays in porous nickel framework foam (Pd/NF). It provides a lot of active sites for H* adsorption and NO 3 - activation leading to a remarkable NH 3 yield rate of 1.52 mmol cm -2  h -1 and a Faradaic efficiency of 78% at -1.4 V versus RHE. Notably, it maintains a high NH 3 yield rate over 50 cycles in 25 h showing good stability. Remarkably, large-area Pd/NF electrode (25 cm 2 ) shows a NH 3 yield of 174.25 mg h -1 , be promising candidate for large-area device for industrial application. In situ FTIR spectroscopy and density functional theory calculations analysis confirm that the enrichment effect of Pd nanorods encourages the adsorption of H species for ammonia synthesis following a hydrogenation mechanism. This work brings a useful strategy for designing NO 3 - RR catalysts of nanorod arrays with customizable compositions.