With these questions in mind, we have studied how the equilibrium potential of HER changes with the salt concentration in LiCl solutions under both acidic and basic conditions with DFTMD simulations. We showed that the intrinsic HER activity goes up significantly with the salt concentration under acidic conditions but keeps relatively constant under alkaline conditions. This reconciles the seemingly contradicting results from previous experimental and computational studies and emphasises the role of water dissociation reaction in the HER activity. Moreover, by exploring finite-field MD simulations of bulk electrolyte solutions, we were able to single out the important contribution of the Poisson potential of liquid phase to the shift of HER potentials in concentrated electrolyte solutions. In particular, it is found that the shifts in the Poisson potential from the neat liquid water to the LiCl electrolyte solution of 9.3 m turn out to be comparable (about 550 mV in the DFT model and about 170 mV in the point-charge model) despite their orders of magnitude difference in absolute value. This highlights the crucial aspect of liquid electrostatic environment for determining the proton reactivity in concentrated electrolyte solutions.