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

Electrochemical nitrate (NO3-) reduction to ammonia (NH3) offers a promising pathway to recover NO3- pollutants from industrial wastewater that can balance the nitrogen cycle and sustainable green NH3 production. However, the efficiency of electrocatalytic NO3- reduction to NH3 synthesis remains low for most of electrocatalysts due to complex reaction processes and severe hydrogen precipitation reaction. Herein, high performance of nitrate reduction reaction (NO3-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 NO3- activation leading to a remarkable NH3 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 NH3 yield rate over 50 cycles in 25 h showing good stability. Remarkably, large-area Pd/NF electrode (25 cm(2)) shows a NH3 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 NO3-RR catalysts of nanorod arrays with customizable compositions.

Automated summary

Electrochemical nitrate (NO3-) reduction to ammonia (NH3) is a promising approach for recovering NO3- pollutants and sustainable NH3 production. However, the efficiency is limited by complex reaction processes and hydrogen precipitation. This study demonstrates high performance nitrate reduction reaction on self-supported Pd nanorod arrays in porous nickel framework foam, achieving a significant NH3 yield rate and stability. Large-area Pd/NF electrode also shows potential for industrial application. The enrichment effect of Pd nanorods promotes H species adsorption for ammonia synthesis.