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

Abstract

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.