Gas bubbles in direct liquid fuel cells: Fundamentals, impacts, and mitigation strategies

The pursuit of carbon neutrality underscores the paramount significance of advancing high-performance direct liquid fuel cells. While several strategies have been established to enhance power generation and stability, including the adoption of new membrane materials, efficient electrocatalysts, innovative cell structures, and alternative reactants, the presence of gas bubbles on the anode remains a significant factor affecting mass transfer and energy efficiency. This review seeks to offer a thorough comprehension of the ramifications of gas bubbles on the cell performance. To achieve this, this review begin by offering an overview of the fundamentals of gas bubble behavior. Subsequently, a detailed analysis of the various ways in which gas bubbles impact fuel cells is presented, encompassing activation losses, ohmic losses, concentration losses, pressure drop, and cell stability. Furthermore, strategies for mitigating the adverse effects of gas bubbles are detailed, encompassing electrode designs, gas diffusion layer designs, anode flow field designs, control of operating parameters, and the application of additional physical fields. Finally, potential avenues for future research in the realm of direct liquid fuel cell applications are outlined, highlighting the ongoing efforts to advance this technology and its role in achieving carbon neutrality.