Modeling of the electrode process in CuCl(aq)/HCl(aq) electrolyzer

Abstract

The electrolysis of CuCl/HCl(aq) is a crucial step in the Cu–Cl thermochemical cycle for hydrogen production. Due to the differing electrolyte flow characteristics between the cathode and anode chambers, the factors influencing their electrolysis efficiency vary accordingly. In this study, we investigated the microphysical properties of the anode separately, as well as the effects of bubbles on the cathode during Cu–Cl electrolysis. The results from both experiments and simulations indicate that at low current densities, increasing temperature and decreasing flow rate facilitate the conversion of Cu ⁺ to Cu²⁺ in the anolyte, with flow rate exerting a more pronounced effect. The accumulation of Cu²⁺ on the electrode surface leads to increased diffusion resistance, which adversely affects mass transfer. At high current densities, the Euler-Euler CFD model combined with particle tracking methods effectively calculated bubble trajectories and velocities within the electrolyzer. The hydrogen volume fraction at the cathode decreased with increasing electrolyte velocity, particularly at higher current densities. The width of the hydrogen bubble curtain diminished as the electrolyte inlet velocity increased. Both the adsorption of hydrogen bubbles on the electrode surface and their dispersion within the electrolyte significantly influence the overpotential.