The coupling of energy-saving small molecule conversion reactions and hydrogen evolution reaction (HER) in seawater electrolytes can reduce the energy consumption of seawater electrolysis and mitigate chlorine corrosion issues. However, the fabrication of efficient multifunctional catalysts for this promising technology is of great challenge. Herein, a heterostructured catalyst comprising CoP and Ni₂P on nickel foam (CoP/Ni₂P@NF) is reported for hydrazine oxidation (HzOR)-assisted alkaline seawater splitting. The coupling of CoP and Ni₂P optimizes the electronic structure of the active sites and endows excellent electrocatalytic performance for HzOR and HER. Impressively, the two-electrode HzOR-assisted alkaline seawater splitting (OHzS) cell based on the CoP/Ni₂P@NF required only 0.108 V to deliver 100 mA·cm⁻², much lower than 1.695 V for alkaline seawater electrolysis cells. Moreover, the OHzS cell exhibits satisfactory stability over 48 h at a high current density of 500 mA·cm⁻². Furthermore, the CoP/Ni₂P@NF heterostructured catalyst also efficiently catalyzed glucose oxidation, methanol oxidation, and urea oxidation in alkaline seawater electrolytes. This work paves a path for high-performance heterostructured catalyst preparation for energy-saving seawater electrolysis for H₂ production.

As an ideal carbon-free energy carrier, ammonia plays an indispensable role in modern society. The conventional industrial synthesis of NH₃ by the Haber–Bosch technique under harsh reaction conditions results in serious energy consumption and environmental pollution. Therefore, it is essential to develop NH₃ synthesis tactics under benign conditions. Electrochemical synthesis of NH₃ has the advantages of mild reaction conditions and environmental friendliness, and has become a hotspot for research in recent years. It has been reported that zinc-nitrogen batteries (ZNBs), such as Zn-N₂, Zn-NO, Zn-NO₃⁻, and Zn-NO₂⁻ batteries, can not only reduce nitrogenous species to ammonia but also have concomitant power output. However, the common drawbacks of these battery systems are unsatisfactory power density and ammonia production. In this review, the latest progress of ZNBs including the reaction mechanism of the battery and reactor design principles is systematically summarized. Subsequently, active site engineering of cathode catalysts is discussed, including vacancy defects, chemical doping, and heterostructure engineering. Finally, some insights are provided to improve the performance of ZNBs from a practical perspective of view.