Abstract
α-SnWO4 is an n-type metal oxide semiconductor that has recently attracted attention as a top absorber material in a D4-tandem device for highly efficient solar water splitting due to the combination of an ideal bandgap (∼1.9 eV) and a relatively negative photocurrent onset potential (∼0 V vs RHE). However, up to now, α-SnWO4 photoanodes have not shown high photoconversion efficiencies for reasons that have not yet been fully elucidated. In this work, phase-pure α-SnWO4 films are successfully prepared by pulsed laser deposition. The favorable band alignment is confirmed, and key carrier transport properties, such as charge carrier mobility, lifetime, and diffusion length are reported for the first time. In addition, a hole-conducting NiOx layer is introduced to protect the surface of the α-SnWO4 films from oxidation. The NiOx layer is found to increase the photocurrent for sulfite oxidation by a factor of ∼100, setting a new benchmark for the photocurrent and quantum efficiency of α-SnWO4. These results p...
Highlights
The storage of solar energy in the form of chemical bonds, as inspired by nature’s photosynthesis, is expected to be a key technology in a future clean energy infrastructure
The NiOx layer is found to increase the photocurrent for sulfite oxidation by a factor of ∼100, setting a new benchmark for the photocurrent and quantum efficiency of α-SnWO4. These results provide important insights into the photoelectrochemical properties and limitations of α-SnWO4 and point toward new strategies to further improve the performance of this promising material
No single photoelectrode material meets all the requirements to be used as a top absorber, but metal oxides have attracted attention in the recent years as potential candidates.[3]
Summary
The storage of solar energy in the form of chemical bonds, as inspired by nature’s photosynthesis, is expected to be a key technology in a future clean energy infrastructure. One possible pathway is direct photoelectrochemical (PEC) water splitting to generate hydrogen, which can be used as a fuel by itself or a feedstock element to produce other fuels (e.g., hydrocarbons through Fischer−Tropsch, ammonia through Haber−Bosch).[1] A key challenge in this approach is the development of a stable and low-cost photoelectrode material with a bandgap of 1.6−2.1 eV that can act as a top absorber in combination with a suitable bottom absorber, such as silicon, in a D4-tandem device.
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