@article{joshi_maggard_2012, title={CuNb3O8: A p-Type Semiconducting Metal Oxide Photoelectrode}, volume={3}, ISSN={["1948-7185"]}, DOI={10.1021/jz300477r}, abstractNote={A new p-type CuNb3O8 polycrystalline photoelectrode was investigated and was determined to have indirect and direct bandgap sizes of 1.26 and 1.47 eV, respectively. The p-type polycrystalline film could be prepared on fluorine-doped tin oxide glass and yielded a cathodic photocurrent under visible-light irradiation (λ > 420 nm) with incident photon-to-current efficiencies of up to ∼6-7% and concomitant hydrogen evolution. A Mott-Schottky analysis yielded a flat band potential of +0.35 V versus RHE (pH = 6.3) and a calculated p-type dopant concentration of ∼7.2 × 10(15) cm(-3). The conduction band energies are found to be negative enough for the reduction of water under visible light irradiation. A hole mobility of ∼145 cm(2)/V·s was obtained from J(I)-V(2) measurements using the Mott-Gurney relation, which is ∼50% higher than that typically found for p-type Cu2O. DFT-based electronic structure calculations were used to probe the atomic and structural origins of the band gap transitions and carrier mobility. Thus, a new p-type semiconductor is discovered for potential applications in solar energy conversion.}, number={11}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Joshi, Upendra A. and Maggard, Paul A.}, year={2012}, month={Jun}, pages={1577–1581} }
 @article{fuoco_joshi_maggard_2012, title={Preparation and Photoelectrochemical Properties of p-type Cu5Ta11O30 and Cu3Ta7O19 Semiconducting Polycrystalline Films}, volume={116}, ISSN={["1932-7447"]}, DOI={10.1021/jp300267v}, abstractNote={New p-type polycrystalline films of semiconducting Cu5Ta11O30 and Cu3Ta7O19 were prepared on fluorine-doped tin oxide (FTO) glass starting from their CuCl-flux synthesis as highly faceted micrometer-sized particles. The particles were annealed on FTO at 400–500 °C, followed by a mild oxidation in air at between 250 and 550 °C. In an aqueous 0.5 M Na2SO4 electrolyte solution (pH = 6.3), the films exhibit strong cathodic photocurrents under irradiation by visible and/or ultraviolet light, which increased with higher annealing and oxidation temperatures owing to increased p-type carrier concentration and better electrical contact between particles. Thermogravimetric analyses show that the oxidation treatments result in an oxygen uptake at concentrations of ∼3 × 1020 cm–3 at 250 °C, to ∼4 × 1021 cm–3 at 550 °C, with the higher temperatures leading to the decomposition of the film. The Cu5Ta11O30 and Cu3Ta7O19 bulk powders exhibit band-gap sizes of ∼2.59 and ∼2.47 eV, respectively, and show an onset of their c...}, number={19}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Fuoco, Lindsay and Joshi, Upendra A. and Maggard, Paul A.}, year={2012}, month={May}, pages={10490–10497} }
 @article{joshi_palasyuk_maggard_2011, title={Photoelectrochemical Investigation and Electronic Structure of a p-Type CuNbO3 Photocathode}, volume={115}, ISSN={["1932-7447"]}, DOI={10.1021/jp204631a}, abstractNote={A new p-type CuNbO3 photoelectrode was prepared on fluorine-doped tin oxide (FTO) glass and characterized by X-ray diffraction (XRD), UV–vis spectroscopy, and photoelectrochemical techniques. Solid-state syntheses yielded a red-colored CuNbO3 phase (space group: C2/m (No. 12), Z = 8, a = 9.525(1) A, b = 8.459(2) A, c = 6.793(1) A, β = 90.9(2)°) with a measured optical bandgap size of ∼2.0 eV. Phase-pure samples could be deposited and annealed on FTO slides at 400 °C under vacuum. Photoelectrochemical measurements showed the onset of a photocathodic current driven under visible-light irradiation and reaching incident-photon-to-current efficiencies exceeding ∼5%. The p-type CuNbO3 film also exhibits a stable photocurrent and notable resistance to photocorrosion, as shown by X-ray diffraction. Electronic structure calculations based on density functional theory reveal the visible-light absorption originates from a nearly direct bandgap transition owing primarily to copper-to-niobium (d10-to-d0) excitations. ...}, number={27}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Joshi, Upendra A. and Palasyuk, Andriy M. and Maggard, Paul A.}, year={2011}, month={Jul}, pages={13534–13539} }
 @article{joshi_palasyuk_arney_maggard_2010, title={Semiconducting Oxides to Facilitate the Conversion of Solar Energy to Chemical Fuels}, volume={1}, ISSN={["1948-7185"]}, DOI={10.1021/jz100961d}, abstractNote={The rising significance of producing useful chemical fuels from sunlight has motivated an upsurge of photochemical research, as shown by the growing diversity of chromophores, redox catalysts, and reactivity studies. However, their synergistic integration within artificial photosynthetic systems requires shareable platforms. Early transition-metal oxides have exhibited effective chromophoric/electronic properties across many systems, which has enabled outstanding photocatalytic water splitting efficiencies, but only under ultraviolet irradiation. Semiconducting modifications of these oxides have been investigated that both extend their absorption deep into the visible region and also closely bracket the redox potentials for water splitting and carbon dioxide reduction. Their coupling to surface-anchored molecular catalysts in order to lower kinetic barriers and provide product selectivity is anticipated to lead to studies involving the dynamic interplay of photons, charge carriers, and catalyst turnover.}, number={18}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Joshi, Upendra A. and Palasyuk, Andriy and Arney, David and Maggard, Paul A.}, year={2010}, month={Sep}, pages={2719–2726} }