Superhydrophilic/superaerophobic NiFe with internal bubble flow channels for electrocatalytic water splitting

The generation and detachment of gas bubbles from electrodes have a substantial impact on mass transfer in electrocatalytic water splitting and superwetting electrodes have emerged as promising solution for addressing such challenge. However, the superhydrophilic or superaerophobic property was mainly related to the structure on the electrode surface, while the bubbles detachment behavior within the bulk space was less investigated. In this study, a three-dimensional NiFe electrode with superhydrophilic/superaerophobic surface and abundant gas channels was constructed via an in-situ bubble template method. The superwetting and hierarchical NiFe/NF can reduce the cumulative adhesion force of bubbles and the gas channels inside the electrode facilitated the transport and release of bubbles driven by the capillary effect. The released bubbles with an average diameter of 30 μm were observed at a current density of 100 mA cm−2. The optimized Ni0.75Fe0.25/NF electrode exhibited promising catalytic activities for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and a high current density of 500 mA cm−2 was achieved with overpotentials of 214 mV and 327 mV, respectively.