Nanostructure of Cr₂CO₂ MXene Supported Single Metal Atom as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Nanostructure-supported single-atom bifunctional catalysts can reduce the usage of catalyst and improve the catalytic activity compared with unifunctional catalysts. Developing effective bifunctional electrocatalysts for water splitting is one of the central issues to the area of renewable energy. Herein, we report a single transition-metal atom anchoring on the Cr₂CO₂ MXene surface as bifunctional eletrocatalyst for water splitting through density functional theory calculations. Results show that Ni anchored on Cr₂CO₂ (Ni/Cr₂CO₂) MXene exhibits satisfactory catalytic activity producing low overpotentials of 0.16 and 0.46 V for HER and OER, respectively. Large amounts of electrons were transferred from Ni to the surface O∗ of Cr₂CO₂, promoting the binding strength between Ni and Cr₂CO₂ (binding energy is -5.16 eV). The ultrahigh Ni oxide formation pressure (O₂ pressure is higher, at 3 × 10¹⁹Pa) ensures the stability of Ni/Cr₂CO₂ during electrocatalytic water splitting. Moreover, ab initio molecular dynamics simulations and climbing nudged elastic band calculations suggest that Ni atom can be stably immobilized on Cr₂CO₂ substrate to prevent its aggregation to form Ni₃ and Ni₄ clusters. In addition, the possible synthesis route is predicted for a Cr₂CO₂-supported Ni single-atom catalyst (SAC) system showing that Ni/Cr₂CO₂ can be experimentally synthesized. This work shows that Cr₂CO₂-supported Ni SAC can be a potential catalyst for water splitting and therefore provides an opportunity for energy conversion.