Computational Hydrogen Electrode (CHE) is a widely-used theoretical framework used for modelling the electrochemical thermodynamics of protoncoupled electron transfer reactions. CHE describes the impact of the electrode potential and pH implicitly by referencing the proton and electron electrochemical potentials against the standard hydrogen electrode using the equilibrium condition μe -+ μH + = 1 2 µ H 2 which defines the potential 0V vs. SHE. Hence, at 0V vs SHE, the free energy of the proton-electron couple can replaced by the free energy of hydrogen gas under standard conditions.