A5038188246- Advanced Photocatalysis Techniques
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- TiO2 Photocatalysis and Solar Cells
- Iron oxide chemistry and applications
- Copper-based nanomaterials and applications
- Electrochemical Analysis and Applications
- Electrocatalysts for Energy Conversion
- Ammonia Synthesis and Nitrogen Reduction
- Organometallic Compounds Synthesis and Characterization
- Electronic and Structural Properties of Oxides
- Quantum Dots Synthesis And Properties
- Crystallography and molecular interactions
- Advanced Nanomaterials in Catalysis
- Corporate Governance and Management
- Organometallic Complex Synthesis and Catalysis
- Synthesis and characterization of novel inorganic/organometallic compounds
- Analytical Chemistry and Sensors
- Mine drainage and remediation techniques
- Perovskite Materials and Applications
- Catalytic Processes in Materials Science
- Porphyrin and Phthalocyanine Chemistry
- Conducting polymers and applications
- Gas Sensing Nanomaterials and Sensors
- Electrochemical sensors and biosensors
Michigan State University
2016-2025
Michigan United
2020-2022
University of Münster
2013-2014
Technische Universität Braunschweig
1990-2008
Northwestern University
2008
Northwest University
2008
California Institute of Technology
2005-2006
University of Massachusetts Amherst
2005
Hematite (α-Fe2O3) constitutes one of the most promising semiconductor materials for conversion sunlight into chemical fuels by water splitting. Its inherent drawbacks related to long penetration depth light and poor charge carrier conductivity are being progressively overcome employing nanostructuring strategies improved catalysts. However, physical–chemical mechanisms responsible photoelectrochemical performance this material (J(V) response) still poorly understood. In present study we...
The most efficient dye-sensitized solar cells (DSSCs) have had essentially the same configuration (nanoparticle TiO2 sensitized with [Ru(4,4′-dicarboxy-2,2′-bipyridine)2(NCS)2] in contact I3−/I−) for last 17 years. In this article we outline strategies improving each of three major photo-relevant components a DSSC, review literature reports consistent these and suggest future directions. Finally explore potential generation DSSCs advancing energy-conversion performance.
Uniform thin films of hematite (α-Fe(2)O(3)) deposited by atomic layer deposition (ALD) coated with varying amounts the cobalt phosphate catalyst, "Co-Pi," were investigated steady-state and transient photoelectrochemical measurements impedance spectroscopy. Systematic studies as a function Co-Pi thickness performed in order to clarify mechanism which enhances water-splitting performance electrodes. It was found that under illumination, catalyst can efficiently collect store photogenerated...
Atomic layer deposition (ALD) was utilized to deposit uniform thin films of hematite (α-Fe2O3) on transparent conductive substrates for photocatalytic water oxidation studies. Comparison the a fast redox shuttle allowed new insight in determining rate limiting processes at electrodes. It found that an additional overpotential is needed initiate compared shuttle. A combination electrochemical impedance spectroscopy, photoelectrochemical and measurements were employed determine cause...
Hematite photoanodes were coated with an ultrathin cobalt oxide layer by atomic deposition (ALD). The optimal coating-1 ALD cycle, which amounts to <1 monolayer of Co(OH)2/Co3O4-resulted in significantly enhanced photoelectrochemical water oxidation performance. A stable, 100-200 mV cathodic shift the photocurrent onset potential was observed that is correlated order magnitude reduction resistance charge transfer at Fe2O3/H2O interface. Furthermore, optical transparency Co(OH)2/Co3O4 coating...
Hematite (α-Fe2O3) thin film electrodes prepared by atomic layer deposition (ALD) were employed to photocatalytically oxidize water under 1 sun illumination. It was shown that annealing at 800 °C substantially improves the oxidation efficiency of ultrathin hematite electrodes. The effect high temperature treatment is remove one two surface states identified, which reduces recombination and Fermi level pinning. Further modification with Co-Pi catalyst resulted in unprecedented photocurrent...
Uniform thin films of hematite and Ti-doped (α-Fe2O3) were deposited on transparent conductive substrates using atomic layer deposition (ALD). ALD's epitaxial growth mechanism allowed the control morphology thickness as well concentration distribution Ti atoms. The photoelectrochemical performances undoped electrodes examined compared under water oxidation conditions. incorporation atoms into was found to dramatically enhance performance, with much greater enhancement for thinnest films. An...
Abstract Artificial photosynthesis via solar water splitting provides a promising approach to storing energy in the form of hydrogen on global scale. However, an efficient and cost-effective production system that can compete with traditional methods using fossil fuels is yet be developed. A photoelectrochemical (PEC) tandem cell consisting p-type photocathode n-type photoanode, photovoltage provided by two photoelectrodes, attractive route achieve highly unassisted at low cost. In this...
Modern dye-sensitized solar cell (DSSC) technology was built upon nanoparticle wide bandgap semiconductor photoanodes. While versatile and robust, the sintered architecture exhibits exceedingly slow electron transport that ultimately restricts diversity of feasible redox mediators. The small collection suitable mediators limits both our understanding an intriguing heterogeneous system performance these promising devices. Recently, a number pseudo-1D photoanodes exhibit accelerated charge...
In this Perspective article we describe how the processes involving redox shuttle—dye regeneration, recombination, and diffusion—affect photovoltaic performance of dye-sensitized solar cells, DSSCs. Key literature on mechanistically complicated, but ubiquitously employed, triiodide/iodide electrolyte is reviewed. Literature examples recent results from our laboratory in utilizing one-electron outersphere shuttles place are then presented.
A series of one-electron outersphere cobalt bipyridyl redox couples were used as shuttles in dye-sensitized solar cells (DSSCs). Atomic layer deposition was to deposit an ultrathin coating alumina on nanoparticle-based TiO2 DSSC photoanodes, which results significantly improved quantum yields for all the DSSCs containing systems. However, a significant discrepancy performance remains between different shuttles. Variation driving force regeneration by ∼500 mV, employing...
Uniform planar films of hematite (α-Fe2O3), deposited by atomic layer deposition, were examined using in situ spectroelectrochemistry during photoinduced water oxidation. A change the absorption spectrum electrodes oxidation was measured under illumination and applied potentials. The correlated to a charge cyclic voltammetry with capacitance impedance spectroscopy. Modification surface alumina reduced feature associated capacitance, suggesting that these features are surface. Comparing...
Atomic layer deposition was used to grow conformal thin films of hematite with controlled thickness on transparent conductive oxide substrates. The were incorporated as photoelectrodes in regenerative photoelectrochemical cells employing an aqueous [Fe(CN)(6)](3-/4-) electrolyte. Steady state current density versus applied potential measurements under monochromatic and simulated solar illumination probe the properties electrodes a function film thickness. Combining results careful optical...
Atomic layer deposition (ALD) has been used to create conformal TiO2 blocking layers on fluorine-doped tin-oxide substrates in dye-sensitized solar cells (DSSCs), effectively eliminating shunting. ALD also deposit, controlled fashion, ultrathin coatings of alumina nanoparticle-based DSSC photoanodes. These modified electrodes enable ferrocenium/ferrocene, an outer-sphere redox couple, be as a shuttle. The photovoltaic performance and interfacial charge-transfer dynamics were investigated...
This article focuses on the promise, problems and progress of utilizing hematite for photocatalyzed water oxidation. Issues which require further research are also presented.
This review describes the potential of hematite as a photoanode material for photoelectrochemical (PEC) water splitting. The current understanding key loss-mechanisms are introduced and correlated to performance enhancement strategies. significant voltage loss associated with overcoming competitive oxidation surface state recombination has recently been surmounted through combination high temperature annealing modification catalysts. Substantial efforts have made at nanostructuring...
Atomic layer deposition is employed to conformally coat low density, high surface area aerogel films with ZnO. The ZnO/aerogel membranes are incorporated as photoanodes in dye-sensitized solar cells, which exhibit excellent power efficiencies of up 2.4% under 100 mW cm−2 light intensity. Supporting information for this article available on the WWW http://www.wiley-vch.de/contents/jc_2089/2008/adma200702781_s.pdf or from author. Please note: publisher not responsible content functionality any...
This article focuses on the promise and progress of replacing ubiquitous triiodide/iodide electrolyte with cobalt poly-pyridine complex redox shuttles in dye-sensitized solar cells, DSSCs. Issues which require further research will also be presented.
Hematite's favorable 2.1 eV band gap, valence position, stability, abundance, and light absorption properties make it a promising semiconductor material for solar-driven water oxidation. While mechanism oxidation at the surface of hematite has not yet been experimentally established, is widely agreed upon that surface-state mediated charge recombination electrode–electrolyte interface competes with This kinetic competition ultimately limits splitting efficiency. The identity role these...
A thorough literature review and the investigation by soft X-ray absorption spectroscopy at synchrotron facilities of Ti-Hematite photoelectrodes are provided.
The mechanism of splitting liquid ammonia is investigated to enable its use for renewable hydrogen storage.