Visible-Light-Active NiV2O6 Films for Photoelectrochemical Water Oxidation

NiV2O6 films were successfully fabricated and characterized as photoanodes for photoelectrochemical (PEC) water oxidation. The films were synthesized by vacuum codeposition of Ni and V followed by annealing in air. The resulting triclinic NiV2O6 films were n-type semiconductors with optical transitions at similar to 2.1 eV (indirect) and 2.4 eV (direct). Photo-electrochemical testing in 1 M KOH showed a photoelectrochemical band gap of similar to 2.4 eV and that similar to 45% of the photocurrent came from light with lambda > 420 nm. NiV2O6 electrodes showed quite stable photo current under bias in basic electrolyte, indicative of chemical stability against photocorrosion despite its relatively small band gap. The flat band potential of NiV2O6 was similar to 0.6 V vs RHE, thus allowing photogenerated holes to oxidize water thermodynamically, and confirmed by oxygen evolution measurements (Faradaic efficiency similar to 80%). Suitable oxygen evolution catalysts and n-type doping are suggested to improve the PEC performance of this material further. Regarding the search for inexpensive photoanodes capable of harvesting photons in the visible region of the solar spectrum, the availability of Ni and V makes NiV2O6 a promising anode material for photoelectrochemical use.