Solar-Driven Gas-Phase Moisture to Hydrogen with Zero Bias

Band structure engineering offers a perfect route to tune the transport properties of electrons and holes independently, especially in semiconductors for water splitting. Here, we explore the possibility of achieving a bias-free single-step solar to chemical energy conversion using gas-phase moisture as the reactant while generating hydrogen as the reaction product. A metal-based superhygroscopic hydrogel scavenges moisture from the ambient environment and serves as the water source. The FeOOH/BiVO4 heterojunction works as the photoanode wherein the interface allows the transport of electrons to the outer layer, resulting in an upward band bending. Concomitantly, the negative charges will accumulate on the Cu2O surface in the FeOOH/Cu2O photocathode, inducing a downward band bending. With the use of the hydrogel, photoanode, and photocathode, a device for directly splitting the moisture absorbed from the ambient air is realized, generating a photocurrent of 0.75 mA cm(-2) under the one-sun intensity of cool daylight without any additional bias. The solar-cell-assisted device can split 6 mg of moisture more than 30 mg of moisture in the same period.

Automated summary

Band structure engineering is utilized to tune the transport properties of materials, enabling the realization of a device that directly splits moisture into hydrogen using solar energy without any external bias. The device demonstrates high efficiency and is able to decompose more moisture compared to traditional methods in the same period of time.