Tandem Effect Promotes MXene‐Supported Dual‐Site Janus Nanoparticles for High‐Efficiency Nitrate Reduction to Ammonia and Energy Output through Zn‐Nitrate Battery

Abstract Electrocatalytic nitrate reduction reaction (NO 3 RR) can convert nitrate contaminants into ammonia with higher added value. However, due to the NO 3 RR involving complex multi‐electron reactions, there is an urgent need to develop efficient electrocatalysts. Herein, CoCu Janus nanoparticles loaded on Ti 3 C 2 T x MXene (CoCu‐Ti 3 C 2 T x ) is synthesized via the combination of molten salt etching and galvanic replacement strategy. The tandem catalysis of CoCu Janus NPs can maintain the balance between nitrogenous intermediates and active hydrogen (H ads ). CoCu‐Ti 3 C 2 T x exhibits a high NH 3 yield of 8.08 mg h −1 mg cat. −1 and a satisfactory Faradaic efficiency of 93.6% at −0.7 V versus reversible hydrogen electrode (RHE). The Zn‐NO 3 − battery assembled with CoCu‐Ti 3 C 2 T x shows an excellent power density of 10.33 mW cm −2 , an NH 3 yield of 1.52 mg h −1 mg cat. −1 and a Faradaic efficiency of 95.3% at 10 mA cm −2 , which enables the simultaneous elimination of nitrate pollutants, ammonia production, and energy supply. Moreover, a series of verification experiments and density functional theory calculation are combined to reveal the reaction path and tandem catalytic mechanism. This work not only provides a new inspiration for the design of tandem catalysts but also promotes the development of Zn‐nitrate battery.