Bubble growth and departure modes on wettable/non-wettable porous foams in alkaline water splitting

•Drastic transition of bubble dynamics on wettable/non-wettable porous electrodes•Significant change overpotential electrodes•Design guideline for high-performance gas-evolving electrodes Electrochemical reactions play a crucial role in many industrial energy conversion and storage processes. The continuous gas production leads to the evolution bubbles at reaction sites, which further result loss due increase transport resistance. To enable electrochemical systems, during have attracted particular interest recently. Yet fundamental relationship among electrode wettability, dynamics, has not been well understood. In this work, we investigate resulting alkaline water splitting by engineering wettability electrode. insights gained from study only shed light fundamentals but also provide design guidelines reactions. Bubble growth departure are ubiquitous phenomena reactions, govern overall mass transport. 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Four foams (0, 0.16 ± 0.02, 0.55 0.03, 0.76 respectively) prepared deposition time (see supplemental experimental procedures S1 details sample preparation characterization), characterized SEM 1C–1F). reason coated selected our system achieve range wettability. tunability state, superhydrophobic, will later, ensures analysis span conditions 2A shows schematic standard three-electrode setup testing S2 setup). (10 mm × 10 mm) horizontally positioned fixture WE. graphite Ag/AgCl counter (CE) RE, respectively. OER polarization curves obtained linear sweep voltammetry scan rate 1 mV/s. calibrated reversible (RHE) equation: ERHE EAg/AgCl 0.197 V 0.059 pH RHE experiments constant (50, 100, 200, 300, mA/cm2) conducted samples 0.76, respectively). visualize high-speed camera (Phantom v7.1, Vision Research Inc.) placed side, digital single-lens reflex (DSLR) (EOS rebel T3, Canon) mounted top, they illuminated diffuse source (Fiber-Lite MODEL3100, Dolan-Jenner Industries). ηtrans subtracting contribution determined impedance spectroscopy (EIS) Tafel fitting without presence bubbles, respectively Figures S3 S4). process performed M solution. 2B function four coverages. overpotential, owing carefully excluded S3). Significant differences wide densities. Specifically, lowest PTFE, over three times 0 0.76. 104 311 mV mA/cm2 increasing difference non-wettable wettable experiment other words, designing equally electrolyzer. Meanwhile, behaviors 2C–2J), strong dependence no 0), smaller (~ 200–700 μm) 2C 2G; see Video visualization). became much larger those condition, 2D 2H; several very (> 2 observed, while surrounding generally (< 2E 2I). Bubbles hemispherical shape behaved similarly condition (≈ 4.5 More interestingly, seen these periodically grew departed WE, remained S5; Videos S4 few shrink associated simultaneous neighboring S5 2K zero mA/cm2. Compared fluctuation higher amplitude lower frequency. frequency consistent inset 2K; S3), overpotential.48Gabrielli Nogueira R.P. Fluctuations 3726-3736Crossref (62) above corresponding overpotentials, leveraging follows study. https://www.cell.com/cms/asset/a12327c0-57ce-4d16-8af2-08c9acec3b84/mmc2.mp4Loading ... Download .mp4 (2.59 MB) Help files S1. side viewThe video speed 0.5 slower real-time speed. frame 50 fps. https://www.cell.com/cms/asset/012ad429-59bf-4bef-8948-b2f6804097d1/mmc3.mp4Loading (2.46 S2. https://www.cell.com/cms/asset/cf26f2c9-e833-4cc2-a517-b3d23d8361b4/mmc4.mp4Loading Downlo