In Situ Reconstructed Cu/Cu₂₊₁O/ZnO Inverse Opals Accelerate Electrocatalytic Nitrate Reduction Kinetics for High Power Zn-NO₃ ^- Battery.

Abstract

The electroreduction of NO₃ ^- to NH₃ (NO₃RR) using renewable energy presents a promising strategy to mitigate environmental pollution and produce high-value chemicals. However, the practical application of NO₃RR is hindered by limited active sites and sluggish reaction kinetics, stemming from the complex eight-electron process. Herein, a novel Cu/Cu₂₊₁O/ZnO-2.5 inverse opals (CCZ-IOs-2.5) catalyst featuring a 3D porous network is designed, which provides abundant active sites and an optimized electronic structure to accelerate the NO₃RR kinetics for efficient NH₃ production. Experimental and theoretical calculations reveal that the introduction of ZnO facilitates electron transfer to Cu active sites, increasing charge density and lowering the reaction energy barrier of the rate-determining step (*NO to *NOH). As a result, CCZ-IOs-2.5 exhibits a notable enhancement in NH₃ yield (from 0.255 to 0.313 mmol h^-1 cm^-2) and Faradaic efficiency (from 85.7% to 95.5%) compared to the Cu/Cu₂₊₁O catalyst. Thanks to its excellent NO₃RR activity, the Zn-NO₃ ^- battery with the CCZ-IOs-2.5 cathode achieves a max power density of 11.93 mW cm^-2. This study adopts a multi-dimensional strategy encompassing morphology regulation, electronic structure optimization, and surface/interface engineering, offering new insights into efficient electrocatalyst development and realizing integrated NH₃ synthesis and energy output in a Zn-NO₃ ^- battery.