Porous and conductive SnO₂ ceramics as a promising nanostructured substrate to host photocatalytic hematite coatings: Towards low cost solar-driven water splitting

Commercially viable generation of “green” hydrogen fuel by solar-driven water splitting requires the design of low-cost photoelectrodes and photo-devices with high photoelectrochemical performance. In this regard, conductive and easily fabricated 3D-oxide ceramics with nanosized grains and high porosity are promising as a substrate with a large surface area to host photocatalytic coatings. To test this approach, hematite photoelectrodes have been grown by metal-organic chemical vapor deposition onto free-standing SnO₂-based ceramics. The photoanodes formed onto Sb₂O₅-SnO₂, CuO-Sb₂O₅-SnO₂, and on MoO₃-Sb₂O₅-SnO₂ substrates in aqueous 1 M NaOH under 1 sun irradiation exhibit photocurrent densities of 0.44 mA/cm², 0.56 mA/cm², and 0.39 mA/cm² at 1.23 V vs. RHE, respectively. The porosity of ceramics results in the 3D growth of a thin hematite coating on ceramic grains in the substrate to a depth of ca. 3 μm. The obtained photoelectrodes are discussed based on the data of photoelectrochemical measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Routes to improved performance are discussed.