The insufficient strategies to improve electronic transport, the poor intrinsic chemical activities, and limited active site densities are all factors inhibiting MXenes from their electrocatalytic applications in terms of hydrogen production. Herein, these limitations are overcome by tunable interfacial chemical doping with a nonmetallic electron donor, i.e., phosphorization through simple heat. treatment with triphenyl phosphine (TPP) as a phosphorous source in 2D vanadium carbide MXene. Through this process, substitution, and/or doping of phosphorous occurs at the basal plane with controllable chemical compositions (3.83-4.84 at%). Density functional theory (DFT) calculations demonstrate that the P-C bonding shows the lowest surface formation energy (Delta G(surf)) of 0.027 eV angstrom(-2) and Gibbs free energy (Delta G(H)) of -0.02 eV, whereas others such as P-oxide and P-V (phosphide) show highly positive Delta G(H). The P3-V2CTx treated at 500 degrees C shows the highest concentration of P-C bonds, and exhibits the lowest onset overpotential of-28 mV, Tafel slope of 74 mV dec(-1), and the smallest overpotential of-163 mV at 10 mA cm(-2) in 0.5 M H2SO4. The first strategy for electrocatalytically accelerating hydrogen evolution activity of V2CTx MXene by simple interfacial doping will open the possibility of manipulating the catalytic performance of various MXenes.