MXenes have attracted attention as promising electrocatalysts
for
performing the hydrogen evolution reaction (HER). However, the poor
intrinsic kinetics and inadequate density of active sites restrict
MXenes as viable electrocatalysts for efficient hydrogen production.
Herein, these hindrances are overcome via tunable doping of anion
atoms as electron donors in titanium carbide (Ti3C2T
X
) MXenes. By engineering the
co-doping of nitrogen and sulfur anions, we achieve efficient electrocatalytic
activity through synergistic chemical and structural changes. The
modified MXene offers an optimal concentration of Ti–S and
Ti–N bonds at the surface of hexagonal nanoplate-decorated
nanosheets, resulting in a low overpotential of 260 mV and a Tafel
slope of 85 mV/dec in an acidic medium, which is improved 3×
over that of the pristine MXene (overpotential of 770 mV). This modified
Ti3C2T
X
catalyst
also displays superior durability compared with other earth-abundant
catalysts, showing an operation for 60 h of continuous hydrogen evolution
without any decay in its performance. The enhanced electrocatalytic
activity of anion-co-doped Ti3C2T
X
MXene is attributed to manipulation of the electronic
structure through synergistic N and S bonding, which promotes balanced
adsorption/desorption of the intermediate hydrogen H* by lowering
the Gibbs free energy (ΔG
H* = −0.07
eV). Our strategy to improve the electrocatalytic activity of Ti3C2T
X
by anion engineering
has the potential to enhance the electrocatalytic activity of numerous
MXenes as well as other high surface area 2D materials.