Nanoflower-Like CuPd/CuO Heterostructure for an Energy-Output Electrocatalytic System Coupling Ammonia Electrosynthesis and Zinc-Nitrate Battery

Abstract

Electrochemical nitrate reduction reaction (NO3RR) can effectively alleviate nitrate pollution and simultaneously realize ammonia electrosynthesis at room temperature. However, it remains a significant challenge for NO3RR to achieve high Faradic efficiency in a full concentration range. Herein, nanoflower-like copper-palladium alloy/CuO heterostructure (CuPd/CuO@NF) is successfully fabricated by the hydrothermal synthesis of CuO nanoflowers and subsequent formation of CuPd alloy. The as-obtained CuPd/CuO@NF exhibits remarkable electrochemical performance for NO3RR in the NO3−-N range from 20 to 1400 ppm, especially with NO3− conversion rate of 97.8% and NH3 selectivity of 99.3% at 20 ppm, Faradic efficiency of 94.2% and NH3 yield rate of 1.37 mmol h−1 cm−2 at 1400 ppm. In-situ Fourier transform infrared spectroscopy and Raman spectra reveal that CuPd/CuO@NF first catalyzes NO3− reduction to NO2−, which is rapidly reduced to NH3 by forming *NH, *NH2, and *NH2OH intermediates. Density functional theory calculations suggest that the NHO route is thermodynamically favorable. When CuPd/CuO@NF is applied in zinc-nitrate battery, it demonstrates a maximum power density of 53.7 mW cm−2, with NO3− conversion of 99.9% and Faradic efficiency of 94.4%. This work offers valuable insights into the design of novel NO3RR electrocatalysts and zinc-nitrate batteries.