Tailoring the electronic structure by transition-metal single atom on Ti3C2O2 for improving hydrogen evolution activity

Highlights: • The electronic structure of oxygen atoms in Ti₃C₂O₂ can be modulated by doping or anchoring TM atom. • The anchored Mn atom optimizes the Gibbs free energy of oxygen sites next nearest to Mn. • Mn@Ti₃C₂O₂ has the low formation energy and exhibits good thermal stability. The development of high efficient and low-cost electrocatalysts for hydrogen evolution reaction (HER) is crucial for boosting the water splitting technology. Based on the density functional theory, we investigate the HER catalytic activity of a serials of transition metal atoms (TM = V, Cr, Mn, Fe, Co, Ni) implanted into or anchored on ${\mathrm{Ti}}_3{C}_2{O}_2$ as a low-cost 2D electrocatalyst with high thermodynamic stability. The results show that compared with the host Ti, the dopant TM donates less electrons to its adjacent oxygen atoms, leading to a stronger H and O bonding, while the anchored TM atom donates excess electrons to its adjacent oxygen atoms, leading to the extremely weak H and O bonding. For TM-anchored ${\mathrm{Ti}}_3{C}_2{O}_2$, those oxygen sites far away from TM exhibit the optimal hydrogen adsorption free energy because of their moderate electrons, indicating that the active sites and catalytic performance of ${\mathrm{Ti}}_3{C}_2{O}_2$ are both modulated by TM atoms.