Papers by Keyword: Solar Water Splitting

Abstract: Several earth-abundant transition-metal oxides (e.g. Fe₂O₃, CoO, and Cu₂O) possessing suitable band gaps for solar water splitting exist, but energy level alignment is often sub-optimal, i.e. the conduction and valence bands do not straddle the water oxidation and reduction potentials. Here, using a nanocrystalline-TiO₂-based photoelectrochemical cell as a model system, we investigate the effect of tuning the semiconductor energy levels by adding Li⁺ ions to the electrolyte. The effect of LiClO₄ addition on band edges, interfacial recombination resistance, electron diffusion length, and charge-separation efficiency were quantified by impedance spectroscopy and analysis of incident photon-to-current efficiency spectra. We find that the TiO₂ band edges are shifted toward positive potentials by the addition of Li⁺, and that this increases the apparent electron diffusion length without affecting the charge-separation efficiency, most likely due to a change in the driving force for O₂ reduction. These results should prove useful in the modeling and optimization of solar water splitting cells employing metal oxide photoelectrodes.

Abstract: Two Oxide Semiconductors, Namely, Bismuth Vanadate (BiVO4) and Silver Bismuth Tungstate (AgBiW2O8) Were Prepared by Solution Combustion Synthesis and their Attributes as Photocatalysts Were Comparatively Evaluated. A Key Conclusion of this Study Is that the Optical Characteristics Alone Provide only a Partial Glimpse into the Applicability of a Given Semiconductor for Solar Energy Conversion and Environmental Remediation. Thus while the Optical Bandgap of Bivo4 Is Lower than Agbiw2o8 (and Thus Is Able to Harness a Greater Portion of the Solar Spectrum), its Photocatalytic Activity for the Degradation of a Dye Is Inferior. this Finding Underlines the Fact that other Characteristics of the Semiconductor (band-Edge Alignment, Surface Quality Etc) Also Play as Critical a Role as the Optical Properties.

Abstract: Recent studies on the molecular mechanism of water photooxidation (or oxygen photoevolution) reaction on TiO2 and related metal oxides or oxynitrides are reviewed. It is shown that a lot of experimental and theoretical studies give definite support to our recently proposed new mechanism, called “nucleophilic attack of H2O” or “Lewis acid-base” mechanism. The new mechanism has the prominent features that it possesses energetic and kinetics different from the conventional electron-transfer mechanism and can explain water photooxidation reaction on visible-light responsive metal oxides or oxynitrides, contrary to the conventional one. The result indicates that the new mechanism is useful for searching for new efficient visible-light responsive materials for solar water splitting.