Interfacial Engineering of W2 N/WC Heterostructures Derived from Solid-State Synthesis: A Highly Efficient Trifunctional Electrocatalyst for ORR, OER, and HER.

To meet the practical demand of overall water splitting and regenerative metal-air batteries, highly efficient, low-cost, and durable electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are required to displace noble metal catalysts. In this work, a facile solid-state synthesis strategy is developed to construct the interfacial engineering of W2 N/WC heterostructures, in which abundant interfaces are formed. Under high temperature (800 °C), volatile CNx species from dicyanodiamide are trapped by WO3 nanorods, followed by simultaneous nitridation and carbonization, to form W2 N/WC heterostructure catalysts. The resultant W2 N/WC heterostructure catalysts exhibit an efficient and stable electrocatalytic performance toward the ORR, OER, and HER, including a half-wave potential of 0.81 V (ORR) and a low overpotential at 10 mA cm-2 for the OER (320 mV) and HER (148.5 mV). Furthermore, a W2 N/WC-based Zn-air battery shows outstanding high power density (172 mW cm-2 ). Density functional theory and X-ray absorption fine structure analysis computations reveal that W2 N/WC interfaces synergistically facilitate transport and separation of charge, thus accelerating the electrochemical ORR, OER, and HER. This work paves a novel avenue for constructing efficient and low-cost electrocatalysts for electrochemical energy devices.