Flow‐engineered multiscale porous electrode design for promoting bubbles removal efficiency toward high‐current–density hydrogen evolution reaction

Abstract Large‐scale hydrogen production through water electrolysis at high current densities encounters significant challenges due to the sluggish bubble dynamics on tortuous nanoporous electrodes, which lead to increased activation loss and structural degradation. Drawing inspiration from the directional fluid transport properties of pipeline structures, this study introduces a bubble‐guiding electrode design by integrating periodic, vertically aligned porous channels into dealloyed nanoporous NiCo alloy (denoted as PA x ‐npNiCo, where x refers to the periodic spacing). The vertically aligned macro‐channels create a split‐path effect for both gas bubbles and electrolyte flow, maintaining stable bubble diffusion velocity and reducing the risk of bubble coalescence. Moreover, nanopores formed through chemical dealloying provide a high density of active sites, significantly boosting hydrogen evolution reaction (HER) performance. By combining high‐speed camera observations with computational fluid dynamics (CFD) simulations, the optimized geometry of the flow‐engineered channels has been identified, demonstrating exceptional bubble‐guiding capabilities. The optimized PA 200 ‐npNiCo electrode, featuring vertically aligned channels with a 200 µm period and three‐dimensional (3D) nanopores on the ligaments, achieves a record current density of 981 mA cm −2 at a low overpotential of 223 mV, while maintaining long‐term stability over 450 h at 500 mA cm −2 . When using PA 200 ‐npNiCo as both the cathode and anode in an electrolyzer, it requires only 1.97 V to achieve 400 mA cm −2 and exhibits stable operation for 100 h at 1000 mA cm −2 . This work offers valuable insights into bubble dynamics for HER and highlights the significance of multiscale porous electrode architecture design for broader electrocatalytic gas‐evolving applications.