title: An Efficient CuxO Photocathode for Hydrogen Production at Neutral pH: New Insights from Combined Spectroscopy and Electrochemistry.
abstract: Light-driven water splitting is one of the most promising approaches for using solar energy in light of more sustainable development. In this paper, a highly efficient p-type copper(II) oxide photocathode is studied. The material, prepared by thermal treatment of CuI nanoparticles, is initially partially reduced upon working conditions and soon reaches a stable form. Upon visible-light illumination, the material yields a photocurrent of 1.3 mA cm(-2) at a potential of 0.2 V vs a reversible hydrogen electrode at mild pH under illumination by AM 1.5 G and retains 30% of its photoactivity after 6 h. This represents an unprecedented result for a nonprotected Cu oxide photocathode at neutral pH. The photocurrent efficiency as a function of the applied potential was determined using scanning electrochemical microscopy. The material was characterized in terms of photoelectrochemical features; X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, fixed-energy X-ray absorption voltammetry, and extended X-ray absorption fine structure analyses were carried out on pristine and used samples, which were used to explain the photoelectrochemical behavior. The optical features of the oxide are evidenced by direct reflectance spectroscopy and fluorescence spectroscopy, and Mott-Schottky analysis at different pH values explains the exceptional activity at neutral pH.
authors.affiliation: Department of Chemistry, University of Milan , Via Golgi 19, 20133 Milan, Italy.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Baran
authors.affiliation: Department of Chemistry, Jagiellonian University , Ingardena 3, 30-060 Krakow, Poland.|SajTom Light Future , 43-354 Czaniec, Poland.
authors.forename: Szymon
authors.initials: S
authors.lastname: Wojtyła
authors.affiliation: CIMAINA, Department of Physics, University of Milan , Via Giovanni Celoria 16, 20133 Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Lenardi
authors.affiliation: Department of Chemistry, University of Milan , Via Golgi 19, 20133 Milan, Italy.|INSTM, National Inter-University Consortium for Materials Science and Technology , Via San Giusti 9, 50121 Florence, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Vertova
authors.affiliation: INSTM, National Inter-University Consortium for Materials Science and Technology , Via San Giusti 9, 50121 Florence, Italy.|Department of Chemistry, University of Pavia , Viale Taramelli 13, 27100, Pavia, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Ghigna
authors.affiliation: Department of Chemistry, University of Pavia , Viale Taramelli 13, 27100, Pavia, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Achilli
authors.affiliation: Department of Chemistry, University of Pavia , Viale Taramelli 13, 27100, Pavia, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Fracchia
authors.affiliation: Department of Chemistry, University of Milan , Via Golgi 19, 20133 Milan, Italy.|INSTM, National Inter-University Consortium for Materials Science and Technology , Via San Giusti 9, 50121 Florence, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rondinini
authors.affiliation: Department of Chemistry, University of Milan , Via Golgi 19, 20133 Milan, Italy.|INSTM, National Inter-University Consortium for Materials Science and Technology , Via San Giusti 9, 50121 Florence, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Minguzzi
keywords: EXAFS; XANES; XPS; copper oxide; hydrogen evolution reaction; photocathode; photoelectrochemical water splitting; scanning electrochemical microscopy