Mean H₂ diffusion rate normalized by the hydrogen molecular number in the present-day terrestrial seawater (N_TO), over the boundary layer overturn time. The solid lines represent the calculation results, and the dashed lines represent the analytical solution without chemical reactions described by Equation (42). The surface temperature is 2400 K, and the initial Fe³⁺/Fe²⁺ ratio is 0.08. Colors indicate different surface H₂ partial pressures.