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Kevin Sivula

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Publications associées (165)

Facile fabrication of tin-doped hematite photoelectrodes - effect of doping on magnetic properties and performance for light-induced water splitting

Michael Graetzel, Kevin Sivula

We present a new, easily scalable method for the deposition of nanocrystalline hematite photoelectrodes based on the spin-coating of a mixed solution containing tin(II) and iron(III) chlorides followed by thermal treatment. Our facile approach does not req ...

Royal Society of Chemistry2012

Correlating long-lived photogenerated hole populations with photocurrent densities in hematite water oxidation photoanodes

Michael Graetzel, Kevin Sivula

Photogenerated charge carrier dynamics are investigated as a function of applied bias in a variety of different hematite photoanodes for solar water oxidation. Transient absorption spectroscopy is used to probe the photogenerated holes, while transient pho ...

2012

Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory

Michael Graetzel, Kevin Sivula, Florian Le Formal, Jérémie Minh-Châu Brillet

An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hem ...

2012

Direct Observation of Two Electron Holes in a Hematite Photoanode during Photoelectrochemical Water Splitting

Michael Graetzel, Kevin Sivula, Artur Braun, Li Zhang, Jin Guo

Visible light active photoelectrodes for hydrogen generation by solar photoelectrochemical water splitting have been under scrutiny for many decades. In particular, the role of electron holes and charge transfer remains controversial. We have investigated ...

American Chemical Society2012

Iron Resonant Photoemission Spectroscopy on Anodized Hematite Points to Electron Hole Doping during Anodization

Michael Graetzel, Philippe Wyss, Kevin Sivula, Qianli Chen, Artur Braun, Li Zhang, Jin Guo

Anodization of a-Fe2O3 (hematite) electrodes in alkaline electrolyte under constant potential conditions the electrode surface in a way that an additional current wave occurs in the cyclic voltammogram. The energy position of this current wave is closely b ...

Wiley-Blackwell2012

LaTiO2N/In2O3 photoanodes with improved performance for solar water splitting

Michael Graetzel, Rosendo Sanjines, Nicolas Xanthopoulos, Kevin Sivula, Takashi Hisatomi

LaTiO2N photoanodes for solar water splitting were prepared by electrophoretic deposition and demonstrated the best photo-currents ever reported for this material. Further important enhancement of the performance was obtained by the use of a sputtered In2O ...

Royal Society of Chemistry2012

Enhancement in the Performance of Ultrathin Hematite Photoanode for Water Splitting by an Oxide Underlayer

Michael Graetzel, Kevin Sivula, Takashi Hisatomi, Morgan Mertens Stefik, Nripan Mathews

Wiley-Blackwell2012

Cathodic shift in onset potential of solar oxygen evolution on hematite by 13-group oxide overlayers

Michael Graetzel, Maurin Cornuz, Kevin Sivula, Florian Le Formal, Jérémie Minh-Châu Brillet, Nicolas Tétreault, Takashi Hisatomi

The onset potential of photoelectrochemical water oxidation on ultrathin hematite was improved by up to 200 mV by the chemical bath deposition of 13-group oxides as overlayers. It is proposed that the corundum-type overlayers released lattice strain of the ...

2011

Passivating surface states on water splitting hematite photoanodes with alumina overlayers

Michael Graetzel, Maurin Cornuz, Kevin Sivula, Florian Le Formal, Nicolas Tétreault, Thomas Moehl

Hematite is a promising material for inexpensive solar energy conversion via water splitting but has been limited by the large overpotential (0.5-0.6 V) that must be applied to afford high water oxidation photocurrent. This has conventionally been addresse ...

2011

Probing the photoelectrochemical properties of hematite (alpha-Fe2O3) electrodes using hydrogen peroxide as a hole scavenger

Michael Graetzel, Kevin Sivula, Scott Charles Warren

We study hematite (alpha-Fe2O3) photoelectrodes for water splitting by examining the fate of photogenerated holes. Using H2O2 as an efficient hole scavenger, we collect all holes that arrive at the electrode/electrolyte interface. This provides the ability ...

2011

Enhanced light harvesting in mesoporous TiO2/P3HT hybrid solar cells using a porphyrin dye

Michael Graetzel, Shaik Mohammed Zakeeruddin, Soo-Jin Moon, Kevin Sivula

We report panchromatic light harvesting in hybrid TiO2/P3HT photovoltaic devices using a porphyrin dye that complements the light absorption of P3HT. The high short circuit photocurrent (12.1 mA cm(-2)) obtained is found to be due, in part, to Forster reso ...

Royal Society of Chemistry2011

Dynamics of photogenerated holes in nanocrystalline alpha-Fe2O3 electrodes for water oxidation probed by transient absorption spectroscopy

Michael Graetzel, Kevin Sivula

Transient absorption spectroscopy on the mu s-s time scale is used to monitor the yield and decay dynamics of photogenerated holes in nanocrystalline hematite photoanodes. In the absence of a positive applied bias, these holes are observed to undergo rapid ...

Royal Society of Chemistry2011

Evolution of an Oxygen Near-Edge X-ray Absorption Fine Structure Transition in the Upper Hubbard Band in alpha-Fe2O3 upon Electrochemical Oxidation

Michael Graetzel, Kevin Sivula, Artur Braun

Electrochemical oxidation of hematite (alpha-Fe2O3) nanoparticulate films at 600 mV vs Ag+/AgCl in KOH electrolyte forms a species at the hematite surface which causes a new transition in the upper Hubbard band between the Fe(3d)-O(2p) state region and the ...

American Chemical Society2011

Photo-assisted electrodeposition of cobalt-phosphate (Co-Pi) catalyst on hematite photoanodes for solar water oxidation

Michael Graetzel, Maurin Cornuz, Kevin Sivula

A photo-assisted electrodeposition approach was used to deposit a cobalt-phosphate water oxidation catalyst ("Co-Pi") onto recently improved dendritic mesostructures of alpha-Fe2O3. A comparison between this approach, electrodeposition of Co-Pi, and Co2+ w ...

2011

Activation Energies for the Rate-Limiting Step in Water Photooxidation by Nanostructured alpha-Fe2O3 and TiO2

Michael Graetzel, Kevin Sivula

Competition between charge recombination and the forward reactions required for water splitting limits the efficiency of metal-oxide photocatalysts. A key requirement for the photochemical oxidation of water on both nanostructured alpha-Fe2O3 and TiO2 is t ...

2011

Highly active oxide photocathode for photoelectrochemical water reduction

Michael Graetzel, Vincent Laporte, Kevin Sivula, Adriana Paracchino

A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection a ...

Nature Publishing Group2011

Light-Induced Water Splitting with Hematite: Improved Nanostructure and Iridium Oxide Catalysis

Michael Graetzel, Maurin Cornuz, Kevin Sivula, Stanley David Tilley

Revved-up rust! Light-induced water splitting over iron oxide (hematite) has been achieved by using a particle-assisted deposition technique and IrO2-based surface catalysis. Photocurrents in excess of 3 mA cm-2 were obtained at +1.23 V versus the reversib ...

Wiley-VCH Verlag GmbH2010

Decoupling Feature Size and Functionality in Solution-Processed, Porous Hematite Electrodes for Solar Water Splitting

Michael Graetzel, Kevin Sivula, Jérémie Minh-Châu Brillet

We introduce a simple solution-based strategy to decouple morphological and functional effects of annealing nanostructured, porous electrodes by encapsulation with a SiO2 confinement scaffold before high temperature treatment We demonstrate the effectivene ...

American Chemical Society2010

Examining architectures of photoanode-photovoltaic tandem cells for solar water splitting

Michael Graetzel, Maurin Cornuz, Jun Ho Yum, Kevin Sivula, Florian Le Formal, Jérémie Minh-Châu Brillet

Given the limitations of the materials available for photoelectrochemical water splitting, a multiphoton (tandem) approach is required to convert solar energy into hydrogen efficiently and durably. Here we investigate a promising system consisting of a hem ...

Cambridge University Press2010

Preferential Orientation in Hematite Films for Solar Hydrogen Production via Water Splitting

Michael Graetzel, Maurin Cornuz, Kevin Sivula

The state-of-the-art performance, obtained through the reduction of precursor gas residence time in hematite photoanodes produced by APCVD, is explained in this report by an enhanced preferential orientation of the highly conductive crystal planes perpendi ...

2010

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