Modification of Hematite Electronic Properties with Trimethyl Aluminum to Enhance the Efficiency of Photoelectrodes.

The electronic properties of hematite were investigated by means of synchrotron radiation photoemission (SR-PES) and X-ray absorption spectroscopy (XAS). Hematite samples were exposed to trimethyl aluminum (TMA) pulses, a widely used Al-precursor for the atomic layer deposition (ALD) of Al2O3. SR-PES and XAS showed that the electronic properties of hematite were modified by the interaction with TMA. In particular, the hybridization of O 2p states with Fe 3d and Fe 4s4p changed upon TMA pulses due to electron inclusion as polarons. The change of hybridization correlates with an enhancement of the photocurrent density due to water oxidation for the hematite electrodes. Such an enhancement has been associated with an improvement in charge carrier transport. Our findings open new perspectives for the understanding and utilization of electrode modifications by very thin ALD films and show that the interactions between metal precursors and substrates seem to be important factors in defining their electronic and photoelectrocatalytic properties.

[1]  R. Liu,et al.  Improving hematite-based photoelectrochemical water splitting with ultrathin TiO2 by atomic layer deposition. , 2014, ACS applied materials & interfaces.

[2]  Omid Zandi,et al.  Enhanced Water Splitting Efficiency Through Selective Surface State Removal. , 2014, The journal of physical chemistry letters.

[3]  F. D. Groot,et al.  The iron L edges: Fe 2p X-ray absorption and electron energy loss spectroscopy , 2013 .

[4]  R. Toth,et al.  Formation of an electron hole doped film in the α-Fe2O3 photoanode upon electrochemical oxidation. , 2013, Physical chemistry chemical physics : PCCP.

[5]  T. Dittrich,et al.  Surface aspects of sol-gel derived hematite films for the photoelectrochemical oxidation of water. , 2013, Physical chemistry chemical physics : PCCP.

[6]  Michael Grätzel,et al.  The Transient Photocurrent and Photovoltage Behavior of a Hematite Photoanode under Working Conditions and the Influence of Surface Treatments , 2012 .

[7]  Coleman X. Kronawitter,et al.  On the Interfacial Electronic Structure Origin of Efficiency Enhancement in Hematite Photoanodes , 2012 .

[8]  J. Bachmann,et al.  Systematic catalytic current enhancement for the oxidation of water at nanostructured iron(III) oxide electrodes , 2012 .

[9]  S. Lany,et al.  Semiconducting transition-metal oxides based on d 5 cations: Theory for MnO and Fe 2 O 3 , 2012 .

[10]  Shaohua Shen,et al.  Surface tuning for promoted charge transfer in hematite nanorod arrays as water-splitting photoanodes , 2012, Nano Research.

[11]  Yichuan Ling,et al.  The influence of oxygen content on the thermal activation of hematite nanowires. , 2012, Angewandte Chemie.

[12]  Juan Bisquert,et al.  Water oxidation at hematite photoelectrodes: the role of surface states. , 2012, Journal of the American Chemical Society.

[13]  S. D. Elliott,et al.  First-Principles Modeling of the “Clean-Up” of Native Oxides during Atomic Layer Deposition onto III–V Substrates , 2012 .

[14]  E. Carter,et al.  Testing variations of the GW approximation on strongly correlated transition metal oxides: hematite (α-Fe2O3) as a benchmark. , 2011, Physical chemistry chemical physics : PCCP.

[15]  S. Bent,et al.  Electron enrichment in 3d transition metal oxide hetero-nanostructures. , 2011, Nano letters.

[16]  C. Adelmann,et al.  Surface chemistry and Fermi level movement during the self-cleaning of GaAs by trimethyl-aluminum , 2011 .

[17]  K. Kukli,et al.  Substrate Reactivity Effects in the Atomic Layer Deposition of Aluminum Oxide from Trimethylaluminum on Ruthenium , 2011 .

[18]  Michael Grätzel,et al.  Solar water splitting: progress using hematite (α-Fe(2) O(3) ) photoelectrodes. , 2011, ChemSusChem.

[19]  E. Carter,et al.  Electron transport in pure and doped hematite. , 2011, Nano letters.

[20]  Michael Grätzel,et al.  Passivating surface states on water splitting hematite photoanodes with alumina overlayers , 2011 .

[21]  Thomas W. Hamann,et al.  Photoelectrochemical investigation of ultrathin film iron oxide solar cells prepared by atomic layer deposition. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[22]  P. Stair,et al.  Adsorption, Desorption, and Reaction of Methyl Radicals on Surface Terminations of α-Fe2O3† , 2010 .

[23]  Anke Weidenkaff,et al.  Photoelectrochemical water splitting with mesoporous hematite prepared by a solution-based colloidal approach. , 2010, Journal of the American Chemical Society.

[24]  Aron Walsh,et al.  Electrodeposited Aluminum-Doped α-Fe2O3 Photoelectrodes: Experiment and Theory , 2010 .

[25]  Michael Grätzel,et al.  Influence of Feature Size, Film Thickness, and Silicon Doping on the Performance of Nanostructured Hematite Photoanodes for Solar Water Splitting , 2009 .

[26]  M. Dupuis,et al.  Electron transfer in environmental systems: a frontier for theoretical chemistry , 2006 .

[27]  K. Cheng,et al.  Quantum size effect on surface photovoltage spectra: alpha-Fe(2)O(3) nanocrystals on the surface of monodispersed silica microsphere. , 2006, The journal of physical chemistry. B.

[28]  Jun Chen,et al.  α‐Fe2O3 Nanotubes in Gas Sensor and Lithium‐Ion Battery Applications , 2005 .

[29]  M. Leskelä,et al.  In Situ Mass Spectrometry Study on Surface Reactions in Atomic Layer Deposition of Al2O3 Thin Films from Trimethylaluminum and Water , 2000 .

[30]  G. Sawatzky,et al.  In situ XPS analysis of various iron oxide films grown by NO2-assisted molecular-beam epitaxy , 1999 .

[31]  Pollak,et al.  X-ray-absorption spectroscopy at the Fe L2,3 threshold in iron oxides. , 1995, Physical review. B, Condensed matter.

[32]  G. Sawatzky,et al.  Oxygen 1s x-ray-absorption edges of transition-metal oxides. , 1989, Physical review. B, Condensed matter.

[33]  Saeki,et al.  Photoemission satellites and electronic structure of Fe2O3. , 1986, Physical review. B, Condensed matter.

[34]  Frank M. F. de Groot,et al.  Multiplet effects in X-ray spectroscopy , 2005 .

[35]  J. Woicik,et al.  Site-specific valence-band photoemission study of α − Fe 2 O 3 , 2002 .