Novel 2D Transition‐Metal Carbides: Ultrahigh Performance Electrocatalysts for Overall Water Splitting and Oxygen Reduction

Searching for highly efficient, stable, and cost‐effective electrocatalysts for water splitting and oxygen reduction reaction (ORR) is critical for renewable energies, yet it remains a great challenge. Here, by performing an unbiased structural search and first‐principles calculations, the electrocatalytic performance of the emerging 2D transitional‐metal carbides, MC2 (M represents the transition metal of Ti, V, Nb, Ta, and Mo, C is carbon), is systematically investigated. Owing to their super stability and outstanding electronic conductivity, fast charge transfer kinetics is allowed during catalysis. Specifically, NbC2, TaC2, and MoC2 possess excellent hydrogen evolution reaction (HER) performance under the reaction by the Volmer‐Heyrovsky mechanism. Moreover, taking advantage of the dual‐active‐site catalytic mechanism for oxygen evolution reaction (OER) and ORR over traditional single‐active‐site mechanism, TaC2 presents promising bifunctional electrocatalytic activity with a low overpotential of 0.06 and 0.37 V for HER and ORR, respectively. Meanwhile, the low overpotential endows MoC2 remarkable multifunctional electrocatalytic performance in overall water splitting (0.001 V for HER, 0.45 V for OER) and ORR (0.47 V). These intriguing results demonstrate the robust applicability of MC2 monolayers as effective electrocatalysts. The electrocatalytic performance of the emerging 2D MC2 structures is explored by performing an unbiased structural search and first‐principles calculations. A series of excellent catalysts are identified, where NbC2 is used for hydrogen evolution reaction (HER), TaC2 for bifunctional catalysis in HER/ oxygen reduction reaction (ORR), and MoC2 for multifunctional catalysis in HER/ oxygen evolution reaction (OER)/ORR. Additionally, the catalytic mechanisms for different reactions are investigated in depth.