Green Hydrogen Production from Water Using PV-Supplied Sono-Electrolysis: A Numerical Modelling Approach of the Effect of Degassing and Mass Transfer

The sono-electrolytic system is complex in terms of heterogeneous fluid flows, particularly due to simultaneous formation and collapse of acoustic cavitation bubbles within an aqueous electrolyte, the evolution of H2 and O2 gases on the electrodes, and the overall bubbling phenomenon. The present study presents a numerical design to investigate the effect of sonication on PV-supplied alkaline electrolysis through a parametric modelling and simulation of the variation of the electrolyte resistance and the kinetics of hydrogen production as functions of bubble degassing, the diffusion coefficient and the Faraday efficiency. The model has been validated through a comparative analysis with experiments. Based on the effect of ultrasound on the diffusion coefficient, the analysis demonstrated that the influence of ultrasound cannot be attributed to an enhancement of mass diffusion. If such an effect exists, its extent remains negligible. Furthermore, the effect of ultrasounds cannot be explained by a change in Faraday efficiency. The comparison of experimental and simulation results shows that the Faraday efficiency remains consistently equal to unity regardless of the presence or absence of ultrasounds. In conclusion, sonication role in sono-electrolysis process is rather due to the degassing effect and hence the reduction of electrode bubble coverage, the bubble resistance, and consequently, the overall ohmic resistance.