Dual-bubble evolution on a platinum microelectrode in water electrolysis

Understanding the dynamics of interacting gas bubbles is crucial for optimizing the efficiency of water electrolysis. This study systematically investigates the evolution behavior of dual hydrogen and oxygen bubbles and their impact on electrolysis performance using dual Pt microelectrodes with a fixed interelectrode distance of 1 mm in 1 mol/L H2SO4 and HNO3 solutions. Using high-speed imaging and electrochemical analysis, three distinct dual-bubble detachment modes are identified under different applied potentials: Mode I (buoyancy-driven detachment), Mode II (buoyancy- and wake effect-driven detachment), and Mode III (coalescence-driven detachment). The results show that the production rates of both H2 and O2 exhibit a nonlinear dependence on the applied potential, with an optimal potential observed for each system. Notably, simultaneous dual-electrode operation does not always enhance efficiency: compared to two independent single electrodes, the efficiency of dual hydrogen bubbles increases by 18% at −3 V in H2SO4 but decreases by 21.1% at −8 V in H2SO4, while that of dual oxygen bubbles decreases by up to 57.6% at 3 V in HNO3. With a fixed interelectrode distance, the performance of the dual-bubble system is governed by two factors: the operating potential, which primarily determines the plateau current magnitude, and the electrolyte type, which influences both the magnitude and direction of the solutal Marangoni force. These findings provide valuable insights into electrolyte selection and operational parameters aimed at enhancing the efficiency of water electrolysis.