Electroanalytical probing of bubble-catalyst interactions on NiIrCo nanostructures for enhanced hydrogen evolution

Understanding and controlling gas bubble dynamics is critical in electrocatalysis, as gas accumulation on catalyst surfaces blocks active sites and degrades catalytic performance. Here, we report both the synthesis of a nanostructured NiIrCo electrocatalyst and, importantly, the systematic electroanalytical investigation of hydrogen bubble desorption dynamics during the hydrogen evolution reaction (HER) in alkaline media. A porous Ni framework was fabricated via hydrogen bubble dynamic templating electrodeposition, followed by galvanic replacement with Ir, and subsequent Co electrodeposition to fabricate NiIrCo with a high electrochemically active surface area. The resulting NiIrCo electrode exhibited excellent HER activity (overpotential −24 mV at 100 mA cm⁻², Tafel slope 21.3 mV dec⁻¹), demonstrating enhanced activity compared to commercial Pt/C (cPt). In addition, bubble desorption was quantitatively evaluated using rotating disk electrode voltammetry, chronopotentiometry, and scanning electrochemical microscopy (SECM). SECM enabled real-time detection of bubble release events, providing localized information on bubble size and detachment frequency. NiIrCo maintained stable voltammetric behavior irrespective of scan rates and rotation speeds, showed minimal potential drift without rotation, and exhibited the highest bubble detachment frequency among all tested electrodes (Ni, NiIr and cPt). These results highlight that compositional/morphological engineering combined with advanced electroanalytical techniques offers a powerful framework for probing interfacial bubble dynamics and guiding the design of efficient HER catalysts.