Superhydrophilic Ni(OH)2/materials of institute lavoisier-100 (Fe) integrated with hydrogel to construct gradient hierarchical pore channels for efficient quasi-solid water splitting

Electrocatalytic water splitting technology is pivotal for building a green and sustainable society. However, practical application has been hindered by insufficient catalyst activity, leakage risks of liquid electrolytes, and interfacial mass transfer limitations. Herein, we designed an electrocatalytic water-splitting device comprising a superhydrophilic/superaerophobic 6‑nickel (II) hydroxide supported on materials of institute lavoisier-100 (Fe) (6-Ni(OH) 2 /MIL-100) catalyst paired with cobalt-modified polyacrylic acid sodium salt (Co-PAAS) hydrogel featured with high ionic conductivity. Through the construction of size-gradient hierarchical pore channels, water directionally transports from the Co-PAAS hydrogel to 6-Ni(OH) 2 /MIL-100, significantly reducing interfacial impedance. The 6-Ni(OH) 2 /MIL-100 catalyst achieves a low overpotentials of 133 mV for the oxygen evolution reaction (OER) and 190 mV for the hydrogen evolution reaction (HER) at 50 mA cm −2 in 1.0 M KOH, with an overall water-splitting cell voltage of 1.520 V. It demonstrates stable operation for 40 h at 1000 mA cm −2 . The Co-PAAS hydrogel exhibits a maximum moisture uptake of 0.40 g g −1 and an exceptional ionic conductivity of 83.3 mS cm −1 . The integrated quasi-solid-state electrolyzer, combining Co-PAAS hydrogel and 6-Ni(OH) 2 /MIL-100, requires only 1.475 V at 50 mA cm −2 and maintains a current density decay rate < 5% after 400 h of continuous operation. This work provides a transformative strategy and theoretical foundation for industrial and portable electrocatalytic water-splitting technology.