Core/shell BCN@Cu heterostructures via electroless deposition for interface-tailored electroactive materials

Boron carbon nitrides (BCN) are semiconductors with tunable electronic band structures, and their heteropolar B and N bonding makes them suitable for electrochemical energy conversion applications. The latter is, however, restricted by poor control over phase formation as the properties of BCN strongly depend on the microstructure and the formed phases. A novel hybrid approach was utilized to control the BCN phase formation by combining mechanical alloying through ball milling and subsequent calcination at 400, 450, and 500 °C. In the next step, a thin layer of copper was deposited onto the BCN particles by electroless plating with and without prior surface activation using Pd²⁺ cations. Copper oxide was deposited on the as-prepared surface, whereas a core/shell Cu@BCN structure was formed by surface activation. The obtained heterostructures were tested in the direct electrochemical reduction of nitrate ions to ammonia (NO₃RR), a reaction of great promise for green ammonia synthesis in the future. Linear sweep voltammetry was carried out in a standard three-electrode electrochemical setup for alkaline NO₃RR at room temperature, and a current density of -19.2 mA cm^-2 at -0.4 (V vs. RHE) and an ammonia faradaic efficiency (FE) and yield of 98.6% and 0.36 μg mg^-1 s^-1 were obtained after a 30 min electrolysis in 0.1 M KNO₃, respectively.