Vacancy-Rich MXene-Immobilized Ni Single Atoms Enable Remarkable Electrocatalytic Oxidation Reaction

Single-atom catalysts (SACs) have recently attracted tremendous attention because of their outstanding catalytic performance in the field of heterogeneous catalysis. Building a strong interaction between the single atom and its supporting matrix is pivotal in stabilizing the single atoms. Herein, we reported the successful synthesis of Ni SACs supported by an emerging Ti₃C₂T<i>_x</i> MXene by using a 'self-reduction' strategy <i>via</i> the assistance of rich Ti vacancies on Ti₃C₂T<i>_x</i> MXene surface, which act as the trap and anchor sites for individual Ni atoms. The constructed Ni SACs supported by the Ti₃C₂T<i>_x</i> MXene show excellent activity and exceptional operational stability toward the hydrazine oxidation reaction. Density functional theory calculations suggested that this remarkable catalytic performance was attributed to the strong coupling of the Ni single atom and its surrounding C atoms, which optimized the electronic density of states that increased adsorption energy and decreased reaction activation energy, thus boosting the electrochemical activity. Results presented here will encourage a broader pursuit of 2D materials-supported SACs designed by a vacancy-trapped strategy combined with the theoretical calculation.