This study addresses a perennial problem in the synthesis of copper vanadates, namely, that of phase purity. A time-efficient solution combustion synthesis (SCS) was employed for obtaining α-CuV2O6 in a polycrystalline powder form in a matter of minutes. Admixture of the final product with α-Cu2V2O7 or V2O5 was avoided by a combination of careful pH control of the SCS precursor mixture and by a postsynthesis NaOH wash. The phase purity of the resultant product was demonstrated by Rietveld refinement of the X-ray diffraction data, energy-dispersive X-ray analyses, and laser Raman spectroscopy. Photoelectrochemical (PEC) measurements showed the material to be an n-type semiconductor. Possible applicability of α-CuV2O6 in PEC devices designed for solar water splitting hinges on a comprehensive study of its structural, optical, magnetic, and optoelectronic attributes; this was done by a combination of theory and experiment. Intensity-modulated photocurrent spectroscopy on thin film samples permitted an assessment of the balance between charge transfer and surface recombination, underlining that the charge separation efficiency determined the photocurrent magnitude. Finally, experiments on the PEC stability of this material on prolonged (∼4 h) irradiation revealed self-healing behavior induced by incipient photocorrosion product layer formation on the oxide semiconductor surface.

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One of the principal challenges for solar-driven hydrogen production via water splitting is to improve the solar-to-hydrogen conversion efficiency. We have employed combinatorial chemistry using a materials inkjet printer, and selected CuBi 2 O 4 as a promising p-type material. The steady-state photocurrent corresponding to water reduction for a 280 nm film at 0.2 V (RHE) was about 0.12 mA cm −2 , significantly lower than that attainable for a 2 eV band gap semiconductor. We have applied intensity-modulated photocurrent spectroscopy (IMPS) to distinguish between the photoelectrochemical processes involved and to determine the associated time constants, in order to gain insight into the loss processes responsible for the low efficiency. The charge separation efficiency reaches up to 0.66 at sufficiently negative potential, however, the recombination rate constant is larger than that corresponding to electron transfer to the solution. This results in a relative charge transfer efficiency of 0.2−0.4, explaining the low photocurrent. At low light intensity, the relative charge transfer efficiency increases up to 0.8, indicating the promise of the material. Interestingly, at sufficiently positive applied potential, the IMPS spectrum of the CuBi 2 O 4 photoelectrode switches sign, indicating a net modulated positive photocurrent. However, the rate constant for hole transfer to the solution is small resulting in a negligible steady-state anodic photocurrent. Strategies to improve the efficiency are discussed.