Abstract
Hydrogen production from humidity in the ambient air reduces the maintenance costs for sustainable solar-driven water splitting. We report a gas-diffusion porous photoelectrode consisting of tungsten trioxide (WO3) nanoparticles coated with a proton-conducting polymer electrolyte thin film for visible-light-driven photoelectrochemical water vapor splitting. The gas–electrolyte–solid triple phase boundary enhanced not only the incident photon-to-current conversion efficiency (IPCE) of the WO3 photoanode but also the Faraday efficiency (FE) of oxygen evolution in the gas-phase water oxidation process. The IPCE was 7.5% at an applied voltage of 1.2 V under 453 nm blue light irradiation. The FE of hydrogen evolution in the proton exchange membrane photoelectrochemical cell was close to 100%, and the produced hydrogen was separated from the photoanode reaction by the membrane. A comparison of the gas-phase photoelectrochemical reaction with that in liquid-phase aqueous media confirmed the importance of the triple phase boundary for realizing water vapor splitting.
Highlights
Large-scale deployment of photocatalytic and photoelectrochemical (PEC) water-splitting technologies, accompanied by fuel cells and energy carrier technologies, will allow the realization of the hydrogen (H2) economy (Maeda and Domen, 2010)
The two compartments of the large proton exchange membranes (PEMs)-PEC cell were pre-purged with water vapor for more than 1 h
We found that the photoresponse of the WO3/Ti fiber photoanode was accelerated by the Nafion ionomer coating, indicating that the electron transfer from water to WO3 was accelerated
Summary
Large-scale deployment of photocatalytic and photoelectrochemical (PEC) water-splitting technologies, accompanied by fuel cells and energy carrier technologies, will allow the realization of the hydrogen (H2) economy (Maeda and Domen, 2010). Stable supply of water might be problematic for large-scale solar H2 production owing to limited rainfall in areas with low-cost land and abundant solar radiation such as deserts (Kumari et al, 2016). Another possible feedstock is seawater, but its use requires purification to avoid problems such as corrosion, poisoning, fouling, and byproduct formation. Gas-phase operations can significantly decrease maintenance costs because the natural convection of air can be used to feed the water vapor and Photoelectrochemical Triple Phase Boundary systems to purify and pump liquid water are not required (Rongé et al, 2014; Modestino et al, 2015)
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