Ionic-Liquid Synthesis of Atomic Molybdenum Nitride Clusters as Bifunctional Oxygen Reduction and Evolution Reactions Electrocatalysts for Alkaline Zn-Air Battery

Transition-metal nitrides (TMNs) have garnered considerable attention for energy conversion applications owing to their exceptional electronic structures and high catalytic activities. However, the scarcity of active sites in TMNs impedes their large-scale application. This study describes the use of wetness impregnation and ionic-liquid methods to enhance the electrocatalytic efficiency of molybdenum nitride (MoN) atomic clusters finely dispersed on nitrogen-doped carbon (MoN@NC) substrates. The as-synthesized electrocatalysts feature atomically dispersed MoN clusters, achieving an impressive onset potential of 0.93 V vs. RHE for the oxygen reduction reaction (ORR) and maintaining an overpotential of just 295 mV at a current density of 10 mA/cm2 for the oxygen evolution reaction (OER). The MoN@NC-based zinc-air battery demonstrated a high-power density of 151 mW/cm2, a robust specific discharge capacity of 759 mAh/gZn at 20 mA/cm2, and superior charge-discharge cycling stability exceeding 190 cycles. The detailed experimental characterization revealed that the uniformly dispersed MoN clusters served as the primary active sites driving the observed catalytic performance. Additionally, the present findings suggested significant correlations between the phase of the material, crystallization, atomic cluster distribution, support porosity, and nitridation temperature. These insights are expected to refine strategies for achieving atomically dispersed nitrides with optimized ORR performance.