Dual strain regulated RhNiAu trimetallene for efficient plasmonic-promoted acidic nitrate electroreduction

Abstract

The nitrate electroreduction reaction (NO₃ERR) under acidic conditions provides a green and sustainable pathway for acidic industrial wastewater treatment and ammonia (NH₃) synthesis. As a typical multi-electron transfer and proton-coupled reaction, acidic NO₃ERR is hindered by the competing hydrogen evolution reaction (HER) and intrinsically slow kinetics. Herein, we report a strategy to regulate the electronic structure of Rh by introducing coupled in-plane and out-of-plane compressive strain into RhNiAu trimetallene (RhNiAu-TML), thereby suppressing HER and accelerating NO₃ERR kinetics. The surface Rh–Au single-atom alloy and subsurface Rh–Ni alloy impart a total compressive strain of 4.1% to RhNiAu-TML. The significantly compressed Rh atoms effectively decrease the formation of underpotentially deposited hydrogen to suppress the Volmer step of HER and reduce the adsorption energy of *NO intermediate to promote its hydrogenation during NO₃ERR, resulting in improved NO₃ERR performance with a high NH₃ Faradaic efficiency of 97.9 ± 2%, a remarkable NH₃ yield rate of 21.6 ± 0.35 mg h⁻¹ mg_cat⁻¹ and outstanding stability for 120 h at +0.05 V versus reversible hydrogen electrode. Additionally, the Au nanocrystal anchored on RhNiAu-TML can result in plasmon-enhanced NO₃ERR, which is further validated in the zinc–nitrate battery, achieving a power density of up to 22.1 mW cm⁻² under light illumination.