Performance Enhancement of Electrocatalytic Hydrogen Evolution through Coalescence-Induced Bubble Dynamics

Journal of the American Chemical Society, vol. 146, pp. 10177–10186

Abstract

High Resolution Image Download MS PowerPoint Slide The evolution of electrogenerated gas bubbles during water electrolysis can significantly hamper the overall process efficiency. Promoting the departure of electrochemically generated bubbles during (water) electrolysis is therefore beneficial. For a single bubble, a departure from the electrode surface occurs when buoyancy wins over the downward-acting forces (e.g., contact, Marangoni, and electric forces). In this work, the dynamics of a pair of H 2 bubbles produced during the hydrogen evolution reaction in 0.5 M H 2 SO 4 using a dual platinum microelectrode system is systematically studied by varying the electrode distance and the cathodic potential. By combining high-speed imaging and electrochemical analysis, we demonstrate the importance of bubble–bubble interactions in the departure process. We show that bubble coalescence may lead to substantially earlier bubble departure as compared to buoyancy effects alone, resulting in considerably higher reaction rates at a constant potential. However, due to continued mass input and conservation of momentum, repeated coalescence events with bubbles close to the electrode may drive departed bubbles back to the surface beyond a critical current, which increases with the electrode spacing. The latter leads to the resumption of bubble growth near the electrode surface, followed by buoyancy-driven departure. While less favorable at small electrode spacing, this configuration proves to be very beneficial at larger separations, increasing the mean current up to 2.4 times compared to a single electrode under the conditions explored in this study.

Authors 7

1. Aleksandr Bashkatov corresponding

   Max Planck University of Twente Center for Complex Fluid Dynamics · University of Twente

   Affiliation as printed

   Physics of Fluids Group, Max Planck Center for Complex Fluid Dynamics and J. M. Burgers Centre for Fluid Dynamics, University of Twente, Enschede 7500 AE, Netherlands

2. Sunghak Park Aachen

   Leiden University

   Affiliation as printed

   Leiden Institute of Chemistry, Leiden University, Leiden 2333 CC, Netherlands

3. Çayan Demirkır

   Max Planck University of Twente Center for Complex Fluid Dynamics · University of Twente

   Affiliation as printed

   Physics of Fluids Group, Max Planck Center for Complex Fluid Dynamics and J. M. Burgers Centre for Fluid Dynamics, University of Twente, Enschede 7500 AE, Netherlands

4. Jeffery A. Wood

   University of Twente

   Affiliation as printed

   Soft Matter, Fluidics and Interfaces, MESA+ Institute for Nanotechnology, J. M. Burgers Centre for Fluid Dynamics, University of Twente, Enschede 7500 AE, Netherlands

5. Marc T. M. Koper Aachen

   Leiden University

   Affiliation as printed

   Leiden Institute of Chemistry, Leiden University, Leiden 2333 CC, Netherlands

6. Detlef Lohse

   Max Planck Institute for Dynamics and Self-Organization · Max Planck University of Twente Center for Complex Fluid Dynamics · University of Twente

   Affiliation as printed

   Max Planck Institute for Dynamics and Self-Organization, Göttingen 37077, Germany

   Physics of Fluids Group, Max Planck Center for Complex Fluid Dynamics and J. M. Burgers Centre for Fluid Dynamics, University of Twente, Enschede 7500 AE, Netherlands

7. Dominik J. Krug corresponding

   Max Planck University of Twente Center for Complex Fluid Dynamics · University of Twente

   Affiliation as printed

   Physics of Fluids Group, Max Planck Center for Complex Fluid Dynamics and J. M. Burgers Centre for Fluid Dynamics, University of Twente, Enschede 7500 AE, Netherlands