1 College of Chemistry and Chemical Engineering, College of Energy Material and Chemistry, Inner Mongolia University, Hohhot 010021, China.
2 Department of Chemical and Materials Engineering, Gina Cody School of Engineering and Computer Science, Concordia University, Montreal, QC H3G 2W1, Canada.
3 State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Wenhua Road 97-1, Zhengzhou 450002, China.
4 School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao 266580, China.

Photoelectrochemical (PEC) water splitting is an attractive strategy to convert solar energy to hydrogen. However, the lifetime of PEC devices is restricted by the photocorrosion of semiconductors and the instability of co-catalysts. Herein, we report a feasible in situ inherent cross-linking method for stabilizing semiconductors that uses a CoFe-dispersed polyacrylamide (PAM) hydrogel as a transparent protector. The CoFe-PAM hydrogel protected BiVO₄ (BVO) photoanode reached a photocurrent density of 5.7 mA cm^-2 at 1.23 V_RHE under AM 1.5G illumination with good stability. The PAM hydrogel network improved the loading of Fe sites while enabling the retention of more CoFe co-catalysts and increasing the electron density of the reaction active sites, further improving the PEC performance and stability. More importantly, by tuning the polymerization network, we pioneer the use of quasi-solid-state electrolytes in photoelectrochemistry, where the high concentration of ionic solvent in the PAM hydrogel ensures effective charge transport and good water storage owing to the hydrophilic and porous structure of the hydrogel. This work expands the scope of PEC research by providing a class of three-dimensional hydrogel electrocatalysts and quasi-solid-state electrolytes with huge extension potential, and the versatility of these quasi-solid-state electrolytes can be employed for other semiconductors.