Article Dans Une Revue Electrochimica Acta Année : 2025

Water electrolysis at near-neutral pH: A semi-empirical modelling strategy to assess the benefit of pressure on cell voltage

Résumé

Water electrolysis for hydrogen production is being deployed using three main technologies: alkaline electrolysis, proton exchange membrane electrolysis, and solid oxide electrolysis. However, electrolysis at near-neutral pH offers an alternative that is safer, more eco-friendly, and requires less capital expenditure. This paper presents the first experimental and theoretical analysis of near-neutral pH water electrolysis under pressure. Pressure can affect the electrolysis cell voltage in three ways: i) it increases the equilibrium voltage, ii) it reduces the negative impact of bubbles that shield part of the electrode surface, and iii) it decreases the negative impact of bubbles on the electrolyte ionic conductivity. Each of these contributions was characterized for gas-evolving electrodes implemented in phosphate pH 7.2 or carbonate pH 10.0, with freely rising bubble layers. In this context, the cell voltage decreased with pressure. Semi-empirical correlations were combined with a simple numerical approach. The resulting model perfectly correlated with the experimental data for pressures ranging from 1 to 4 bar and current densities from 500 to 2000 A m -². The model demonstrated that the beneficial effect of pressure on the freely rising bubble layers was the predominant contribution, and that the corresponding gain increases with the applied current density. At 2000 A m -2 , it was possible to achieve up to a 400 mV reduction in cell voltage by operating under 4 bar instead of atmospheric pressure. The power savings can reach 0.7 kWh per Nm³ of hydrogen produced, representing a considerable gain in comparison to the energy generally consumed by water electrolysis.

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hal-05064586 , version 1 (12-05-2025)

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Junzhe Sun, Luc Etcheverry, Alain Bergel. Water electrolysis at near-neutral pH: A semi-empirical modelling strategy to assess the benefit of pressure on cell voltage. Electrochimica Acta, 2025, 530, pp.146264. ⟨10.1016/j.electacta.2025.146264⟩. ⟨hal-05064586⟩
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