Multiphysics Model of Photoelectrochemical Water Splitting under Concentrated Sunlight and Near-Neutral Conditions

Photoelectrochemical water splitting provides a sustainable pathway toward green hydrogen, especially under concentrated sunlight and near-neutral conditions. However, most multiphysics models neglect these conditions and address only one electrolysis compartment rather than the entire cell, limiting a comprehensive understanding of full-cell multiphysics interactions. Herein, an integrated multiphysics model is developed, simulating PEC water splitting under concentrated illumination and near-neutral conditions. Our model reveals nonlinear photocurrent enhancement, primarily constrained by voltage losses across the electrolyte and conductive substrates. Importantly, mass transfer behaviors near the photoanode and cathode exhibit notable asymmetry, arising from the directional buffering capacity differences of the electrolyte under varying local pH conditions and distinct physical properties and generation rates of hydrogen and oxygen gases. While bubble-induced convection improves local mass and heat transport, bubble accumulation simultaneously reduces the electrolyte conductivity, especially near catholyte outlets. By quantitatively analyzing these coupled phenomena, this study provides valuable insights toward understanding and optimizing the PEC system.