MOFs-Assisted Synthesis of Hierarchical Porous Nickel–Cobalt Nitride Heterostructure for Oxygen Reduction Reaction and Supercapacitor

Ever-increasing energy needs together with environmental concerns have accelerated development of alternative energy solutions, including storage and conversion. One such solution is usage of supercapacitors (SCs) and fuel cells. This work focuses on a novel fabrication of metal–organic frameworks (MOFs) to incorporate nickel–cobalt nitride (Ni-CoN) into N-doped carbon (NC). The resulting Ni-CoN@NC nanostructures, consisting of Ni3N and CoN nanoparticles (NPs) along with conductive NC derived from MOFs, demonstrated an outstanding electrochemical activity as oxygen reduction reaction (ORR) catalysts and as bifunctional materials for supercapacitors. This work presents a practical method for using MOFs as a "bridge" to synthesize metal nitrides with conductive framework to be used for efficient electrochemical energy storage. Synergistic effects resulting from a combination of nitride NPs and N-doped porous carbon provided the resulting Ni-CoN@NC composites with excellent ORR catalytic activity with onset potential of 0.97 V (vs RHE), half-wave potential of 0.84 V, and durability. An improved capacitance was also successfully obtained for SCs, which was significantly better than capacitance of the majority of nitride-based electrodes. Such excellent performance of this novel composite material makes it very appealing for future generations of energy conversion and storage devices.