A Solid Electrolyte for Photocatalytic Devices With a Hydrogen Evolution Rate of ≥43 μmol h−1 Under Real Sunlight

Abstract

The practical application of gas–solid photocatalytic hydrogen evolution is often limited by low water vapor utilization efficiency and the absence of continuous proton transport pathways. To mitigate these issues, we developed a solid-state electrolyte based on a silica aerogel–potassium acetate composite. This electrolyte exhibits an ionic conductivity of 9.6 × 10⁻⁴ S cm⁻¹ and an interfacial double-layer capacitance of 2480 μF cm⁻². Its hierarchical meso-macroporous network facilitates the capture and capillary condensation of atmospheric water vapor, which establishes localized aqueous pathways for proton conduction. Integrating this composite electrolyte with a CsPbBr₃-based photoactive layer to form an all-solid-state photocathode led to a notable suppression of charge recombination. This effect is attributed to the use of acetate ions as effective hole traps at the solid–solid interface. Consequently, the device achieved a steady-state hydrogen evolution rate of 43.4 μmol h⁻¹ under simulated sunlight (AM 1.5 G), corresponding to a solar-to-hydrogen (STH) conversion efficiency of 0.64%. This performance remained stable, with less than 40% decay, over continuous operation for 100 h, demonstrating the robustness afforded by the solid-state design.