Katarzyna Skorupska - Academia.edu (original) (raw)
Papers by Katarzyna Skorupska
Processes, relevant for light induced fuel generation water photoelectrolysis, CO2 reduction are ... more Processes, relevant for light induced fuel generation water photoelectrolysis, CO2 reduction are shortly reviewed. Stabilization strategies for development of efficient tandem cell structures that are based on non oxidic semiconductors are presented. The recently introduced nanoemitter concept that involves surface passivation by a nanoporous film is described and first results on light induced hydrogen generation with p Si 100 and p InP 100 2x4 thin films are given. Solar to hydrogen efficiencies reach 14 for homoepitaxial InP thin films covered with Rh nanoislands. In the pursuit to develop biologically inspired systems, successful enzyme immobilization at an electrochemically nanostructured Si surface that shows step bunching has been achieved as evidenced by tapping mode atomic force microscopy
Electrocatalysis, 2010
A new concept of fabrication, immobilization, and distribution of bimetallic PtRu nanoparticles l... more A new concept of fabrication, immobilization, and distribution of bimetallic PtRu nanoparticles leading to enhancement of the electrocatalytic oxidation of ethanol is proposed. The approach utilizes poly (diallyldimethylammonium chloride), PDDA, to functionalize multi-walled carbon nanotubes (MWCNTs) and to produce a novel support for synthesized PtRu nanoparticles as well as further modification of the catalytic surfaces with ultra-thin layers of phosphododecamolybdate (PMo 12 O 40 3− ). Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed.
ECS Transactions, 2013
ABSTRACT In the present work we explore the phosphododecamolybdate heteropolyblue-mediated synthe... more ABSTRACT In the present work we explore the phosphododecamolybdate heteropolyblue-mediated synthesis of gold nanoparticles, acting as a new generation electrocatalytic system exhibiting appreciable activity toward reduction of carbon oxide (IV) and reduction of oxygen (after combining with Co-porphyrin). We explore the ability of highly-concentrated Keggin-type phosphomolybdates to attach within the plain gold surfaces to achieve the highly shape-selective synthesis of approximately spherical or anisotropic Au nanostructures of controlled sizes. The tunable concentrations of reducing (and stabilizing) agent H3[H4P(MoV)4(Mo VI)8O40] allowed us to produce a wide range of nanostructured gold with specific sizes and shapes. The aim of this work was to study the applicability of phosphomolybdate-protected gold nanoparticles to create microporous matrix for reduction of carbon dioxide and the active support for the Co-porphyrin catalytic centers towards reduction of oxygen. Keggin-type structures-stabilizing gold nanoparticles were expected to provide electrons and mobile protons to the vicinity of Co-porphyrin, while gold nanoparticles were responsible for high electronic conductivity combined with electrocatalytic activity towards CO2 and H2O2 reduction. The hybrid catalyst based on Co-porphyrin and phosphomolybdate-protected gold nanoparticles led to synergistic effect that was evident from some positive shift of the oxygen reduction voltammetric potentials and significant increase of the voltammetric currents in all case.
Superlattices and Microstructures, 2004
The initial processes leading from an atomically flat Si surface to porous silicon formation are ... more The initial processes leading from an atomically flat Si surface to porous silicon formation are not well known and detailed surface analytical investigations on the dissolution steps are still lacking. By performing electrochemical experiments in dilute ammonium fluoride solutions at moderate pH values, we are able to investigate the process of dissolution from first pit formation to the formation of transitory mesa-type terraces on atomically flat n-Si(111) by atomic force microscopy. Mesa-type structures with flat extended terraces surrounded by strongly corrugated areas are observed after different conditioning procedures. The mesas exhibit terrace edges aligned with respect to preferred surface orientations, which results in pentagonal, hexagonal or higher composed structures. The findings can be interpreted in terms of the formation of sidewalls exhibiting only a limited number of crystal orientations: {111}, {110} and {113}. Because these faces can be electrochemically H terminated in a 1×1 manner, we suggest that their stability accounts for the variety of observed structures.
ECS Transactions, 2007
Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation ... more Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation of nanoporous oxides. Metal electrodeposition into these pores results in local Schottky junction formation. Metal nanoemitters are contacted with a transparent conductive oxide and aluminum contact fingers for preparation of the first device (Al/ZnO/Pt-SiO 2 /Si/GaIn/Ag). Present solar-toelectrical conversion efficiencies are small and various improvement possibilities are outlined.
ECS Transactions, 2014
ABSTRACT
ECS Transactions, 2009
ABSTRACT The formation of step bunching was observed by atomic force microscopy on n type Si 111 ... more ABSTRACT The formation of step bunching was observed by atomic force microscopy on n type Si 111 surfaces during the electrodeposition of noble metals under semiconductor depletion conditions. The surface chemical analysis performed by synchrotron radiation photoelectron spectroscopy SRPES indicates the formation of an ultra thin oxide film along with the topological transformation. Step bunching is interpreted in terms of site specific etching controlled by the reactivity of kink sites and step edges together with the surface accumulation of holes supplied by the reduction of Pt chloride complexes via the valence band
ECS Transactions, 2014
ABSTRACT The successful preparation of a nanohybrid electrode made from Ta3N5 nanoparticle powder... more ABSTRACT The successful preparation of a nanohybrid electrode made from Ta3N5 nanoparticle powders interlinked by Nafion is described. The basic photoelectrochemical properties as anode for water photolysis are investigated and gas evolution as well as corrosion reactions are determined by differential electrochemical mass spectroscopy (DEMS) and X-ray photoelectron spectroscopy (XPS). The sample shows oxygen evolution but also photocorrosion, oxidation of the Ta3N5 nanoparticles via the O ls line in XPS experiment. The photocorrosion reaction results in a core-shell structure consisting of a tantalum oxide shell and a tantalum nitride core as seen in XPS and x-ray diffraction.
Solid State Ionics, 2000
A series of alkaline thin-film solid electrolytes, based on poly(vinyl alcohol) (PVA), potassium ... more A series of alkaline thin-film solid electrolytes, based on poly(vinyl alcohol) (PVA), potassium hydroxide (KOH) and water (PVA–KOH–H2O) were prepared. Their conductivity was studied using complex impedance method. The most conducting foils were composed of ca. 40 wt.% of PVA, 25–30 wt.% of KOH, and 30–35 wt.% of water. Typical conductivity of such foils reached the level of nearly 10−3 Ω−1cm−1 at room temperature. Temperature dependence of the conductivity was found to be in agreement with the Arrhenius expression with the activation energy of the order of 28–22 kJmol−1, depending on the electrolytes composition. The electrochemical stability window at the metal/electrolyte interface is of 1.5 V for stainless steel and nickel, and of 1.7 and 2.75 V for platinum and gold, respectively. Such alkaline electrolytes are interesting from the point of view of their potential application in all-solid rechargeable alkaline batteries as well as in small electrochemical devices, such as chemical capacitors, electrochromic or photogalvanic devices.
physica status solidi (b), 2010
ABSTRACT Topographical and electronic and properties of step bunched Si(111), prepared by electro... more ABSTRACT Topographical and electronic and properties of step bunched Si(111), prepared by electrochemical processing in alkaline solution, are analyzed. Tapping mode atomic force microscopy (TM AFM) analysis shows that one bunched step consists of about 15 atomic steps (each 0.314 nm in height) and that the (111) oriented terraces have widths that range from 150 to 250 nm. Scanning tunneling microscopy (STM) experiments show a corrugation of the (111) terraces with an rms roughness of 0.5–0.8 nm, correlated with etch pits in alkaline solution. Low energy electron diffraction (LEED) data show a splitting of the (10) and (01) spot from which a minimum terrace width of 4.8 nm have been calculated in good agreement with the TM AFM data. Kelvin probe force microscopy (KPFM) experiments show a decrease of the contact potential difference (CPD) at and near the edges of steps indicating a more negatively charged surface area. Synchrotron radiation photoelectron spectroscopy (SRPES) on electrochemically and purely chemically prepared step bunched surfaces is compared. From the Si 2p core level shift, and, in particular, from the onset of the valence band emission, an accumulation layer-type shift is observed on the electrochemically prepared sample that is absent for chemical preparation. The move of the Fermi level toward the conduction band minimum of the electrochemically conditioned samples is interpreted by H incorporation and discussed by a doping model that involves the mechanism of hydrogen evolution.
Thin Solid Films, 2005
Investigations on how to replace the toxic KCN etching for the removal of Cu–S phases during the ... more Investigations on how to replace the toxic KCN etching for the removal of Cu–S phases during the preparation of CuInS2 (CIS) absorber layers by electrochemical procedures are presented. Starting from a simple anodic treatment in V2+/V3+ electrolyte, a more complex photoelectrochemical technique is developed which consists of different consecutive etching steps for the dissolution of the predominant CuS and for
The Journal of Physical Chemistry C, 2013
ABSTRACT Oxidation and dissolution phenomena of Si(111) in alkaline electrolyte are investigated ... more ABSTRACT Oxidation and dissolution phenomena of Si(111) in alkaline electrolyte are investigated by a combination of photoelectrochemistry, scanning probe microscopy (SPM), transmission electron microscopy (TEM) and in-system synchrotron radiation photoelectron spectroscopy (SRPES). The surface topography in the initial anodic potential regime shows the formation of mesoscale pores with widths in the range 300–500 nm and partial surface oxidation. The surface chemistry assessment by SRPES shows patchy silicon oxide growth, suboxides, and remnants of the former hydrogen terminated surface areas. The use of the obtained self-organized nanostructures for application in nanoemitter photocatalytic solar cells is discussed. The necessary requirements regarding the total surface area of electrocatalysts needed to sustain the current density due to light-induced excess minority carriers in conjunction with the exchange current density of the considered heterogeneous catalysts is discussed.
The Journal of Physical Chemistry C, 2014
Physica Scripta, 2009
Step-bunched Si surfaces with step heights of ~3 nm have been prepared as substrates for immobili... more Step-bunched Si surfaces with step heights of ~3 nm have been prepared as substrates for immobilization of the enzyme reverse transcriptase of the avian myeloblastosis virus. Tapping mode atomic force microscopy has been used for imaging. Calibration experiments using the carrier solution without the enzyme show the preservation of the surface without organic contamination. Upon enzyme deposition, two specific shapes
Journal of Solid State Electrochemistry, 2009
Photoelectrochemically prepared nanotopographies on semiconductors are used for realization of na... more Photoelectrochemically prepared nanotopographies on semiconductors are used for realization of nanoemitter solar devices that are active in the photovoltaic and the photoelectrocatalytic mode. The development of solar devices by a nonlinear electrochemical process and combined chemical/electrochemical metal deposition is described. Based on this low-temperature scalable approach, first efficiencies of 7.3% in the photovoltaic mode are reported for the photoelectrochemical solar cell n-Si/SiO 2 /Pt/I 3 − -I − . With p-Si/Pt nanocomposite structures, light-induced H 2 evolution is achieved. The surface chemistry and morphology is analyzed by photoelectron spectroscopy (PES), Fourier transform infrared spectroscopy, and high-resolution scanning electron microscopy. The operational principle of Pt-based nanoemitter solar devices that use silicon single crystal absorbers is analyzed by Mott-Schottky plots, chronoamperometric profiles, and PES. Related to simultaneous oxide formation during Pt deposition, evidence for the formation of a metal-oxide-semiconductor junction is obtained that explains the observed electronic behavior.
Journal of Materials Chemistry, 2012
An electrochemically functionalized surface of p-type silicon was used as a nanostructured materi... more An electrochemically functionalized surface of p-type silicon was used as a nanostructured material for immobilization and activation of a redox metalloprotein. A protocol resulting in the stable enzyme adsorption and utilization was applied to Trametes versicolor laccase (TvL), the ''blue'' coppercontaining oxidase enzyme, a model bio-electrocatalyst for oxygen reduction. The obtained system was tested as a photocatalytic electrode for oxygen sensing through its electroreduction at copper ionic active sites following illumination with visible light. Processes related to the photoexcitation and charge separation occur within the semiconductor (SC) material. Direct, rather than mediated by 2,2 0azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), electron transfers from the semiconductor to the enzyme were observed. The topography of the p-Si substrate was assessed by transmission electron microscopy (TEM) and tapping mode atomic force microscopy (TM AFM) methods. The electronic properties of the systems were tested using synchrotron radiation photoelectron spectroscopy (SRPES). The nature of the biomolecule immobilization was studied by TM AFM.
Journal of The Electrochemical Society, 2009
ABSTRACT Ir nanoislands were electrodeposited from chloride solutions on n type Si 111 surfaces. ... more ABSTRACT Ir nanoislands were electrodeposited from chloride solutions on n type Si 111 surfaces. The conditioned surface was investigated by electrochemical capacitance measurements, ex situ atomic force microscopy, high resolution transmission electron microscopy, and in system synchrotron radiation photoelectron spectroscopy SRPES . The growth of metal particles was accompanied by the formation of an ultrathin oxide layer, conforming to nanodimensioned metal oxide semiconductor MOS junctions. SRPES Si core level spectra obtained with surface sensitive excitation energies show the presence of a SiO2 signal with 30 40 of the oxide signal contribution arising from intermediate oxidation states Si , Si2 , and Si3 . The valence band spectrum reveals that the Fermi level of silicon is pinned at the gap states of the Si SiO2 interface at 0.6 eV above the valence band, driving the semiconductor under depletion. The presence of metal particles induces a lateral modulation of the interfacial electric field by the formation of nanoscaled MOS junctions with a Schottky barrier of 0.84 eV, as assumed by extrapolating the behavior of full covered solid state MOS junctions
Journal of Electroanalytical Chemistry, 2011
The development of hybrid biological – inorganic semiconductor structures towards biophotoelectro... more The development of hybrid biological – inorganic semiconductor structures towards biophotoelectrocatalytically active systems is described. The aspect of immobilization is analyzed using the heterodimer reverse transcriptase of the avian myeloblastosis virus (RT AMV), deposited onto step-bunched Si(111) and the defect-rich layered semiconductor MoTe2. Surface site specific adsorption is observed in high-resolution tapping mode atomic force microscopy (TM-AFM) measurements of AMV
Processes, relevant for light induced fuel generation water photoelectrolysis, CO2 reduction are ... more Processes, relevant for light induced fuel generation water photoelectrolysis, CO2 reduction are shortly reviewed. Stabilization strategies for development of efficient tandem cell structures that are based on non oxidic semiconductors are presented. The recently introduced nanoemitter concept that involves surface passivation by a nanoporous film is described and first results on light induced hydrogen generation with p Si 100 and p InP 100 2x4 thin films are given. Solar to hydrogen efficiencies reach 14 for homoepitaxial InP thin films covered with Rh nanoislands. In the pursuit to develop biologically inspired systems, successful enzyme immobilization at an electrochemically nanostructured Si surface that shows step bunching has been achieved as evidenced by tapping mode atomic force microscopy
Electrocatalysis, 2010
A new concept of fabrication, immobilization, and distribution of bimetallic PtRu nanoparticles l... more A new concept of fabrication, immobilization, and distribution of bimetallic PtRu nanoparticles leading to enhancement of the electrocatalytic oxidation of ethanol is proposed. The approach utilizes poly (diallyldimethylammonium chloride), PDDA, to functionalize multi-walled carbon nanotubes (MWCNTs) and to produce a novel support for synthesized PtRu nanoparticles as well as further modification of the catalytic surfaces with ultra-thin layers of phosphododecamolybdate (PMo 12 O 40 3− ). Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed.
ECS Transactions, 2013
ABSTRACT In the present work we explore the phosphododecamolybdate heteropolyblue-mediated synthe... more ABSTRACT In the present work we explore the phosphododecamolybdate heteropolyblue-mediated synthesis of gold nanoparticles, acting as a new generation electrocatalytic system exhibiting appreciable activity toward reduction of carbon oxide (IV) and reduction of oxygen (after combining with Co-porphyrin). We explore the ability of highly-concentrated Keggin-type phosphomolybdates to attach within the plain gold surfaces to achieve the highly shape-selective synthesis of approximately spherical or anisotropic Au nanostructures of controlled sizes. The tunable concentrations of reducing (and stabilizing) agent H3[H4P(MoV)4(Mo VI)8O40] allowed us to produce a wide range of nanostructured gold with specific sizes and shapes. The aim of this work was to study the applicability of phosphomolybdate-protected gold nanoparticles to create microporous matrix for reduction of carbon dioxide and the active support for the Co-porphyrin catalytic centers towards reduction of oxygen. Keggin-type structures-stabilizing gold nanoparticles were expected to provide electrons and mobile protons to the vicinity of Co-porphyrin, while gold nanoparticles were responsible for high electronic conductivity combined with electrocatalytic activity towards CO2 and H2O2 reduction. The hybrid catalyst based on Co-porphyrin and phosphomolybdate-protected gold nanoparticles led to synergistic effect that was evident from some positive shift of the oxygen reduction voltammetric potentials and significant increase of the voltammetric currents in all case.
Superlattices and Microstructures, 2004
The initial processes leading from an atomically flat Si surface to porous silicon formation are ... more The initial processes leading from an atomically flat Si surface to porous silicon formation are not well known and detailed surface analytical investigations on the dissolution steps are still lacking. By performing electrochemical experiments in dilute ammonium fluoride solutions at moderate pH values, we are able to investigate the process of dissolution from first pit formation to the formation of transitory mesa-type terraces on atomically flat n-Si(111) by atomic force microscopy. Mesa-type structures with flat extended terraces surrounded by strongly corrugated areas are observed after different conditioning procedures. The mesas exhibit terrace edges aligned with respect to preferred surface orientations, which results in pentagonal, hexagonal or higher composed structures. The findings can be interpreted in terms of the formation of sidewalls exhibiting only a limited number of crystal orientations: {111}, {110} and {113}. Because these faces can be electrochemically H terminated in a 1×1 manner, we suggest that their stability accounts for the variety of observed structures.
ECS Transactions, 2007
Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation ... more Oscillatory behaviour of silicon electrodes in fluoride containing solution results in formation of nanoporous oxides. Metal electrodeposition into these pores results in local Schottky junction formation. Metal nanoemitters are contacted with a transparent conductive oxide and aluminum contact fingers for preparation of the first device (Al/ZnO/Pt-SiO 2 /Si/GaIn/Ag). Present solar-toelectrical conversion efficiencies are small and various improvement possibilities are outlined.
ECS Transactions, 2014
ABSTRACT
ECS Transactions, 2009
ABSTRACT The formation of step bunching was observed by atomic force microscopy on n type Si 111 ... more ABSTRACT The formation of step bunching was observed by atomic force microscopy on n type Si 111 surfaces during the electrodeposition of noble metals under semiconductor depletion conditions. The surface chemical analysis performed by synchrotron radiation photoelectron spectroscopy SRPES indicates the formation of an ultra thin oxide film along with the topological transformation. Step bunching is interpreted in terms of site specific etching controlled by the reactivity of kink sites and step edges together with the surface accumulation of holes supplied by the reduction of Pt chloride complexes via the valence band
ECS Transactions, 2014
ABSTRACT The successful preparation of a nanohybrid electrode made from Ta3N5 nanoparticle powder... more ABSTRACT The successful preparation of a nanohybrid electrode made from Ta3N5 nanoparticle powders interlinked by Nafion is described. The basic photoelectrochemical properties as anode for water photolysis are investigated and gas evolution as well as corrosion reactions are determined by differential electrochemical mass spectroscopy (DEMS) and X-ray photoelectron spectroscopy (XPS). The sample shows oxygen evolution but also photocorrosion, oxidation of the Ta3N5 nanoparticles via the O ls line in XPS experiment. The photocorrosion reaction results in a core-shell structure consisting of a tantalum oxide shell and a tantalum nitride core as seen in XPS and x-ray diffraction.
Solid State Ionics, 2000
A series of alkaline thin-film solid electrolytes, based on poly(vinyl alcohol) (PVA), potassium ... more A series of alkaline thin-film solid electrolytes, based on poly(vinyl alcohol) (PVA), potassium hydroxide (KOH) and water (PVA–KOH–H2O) were prepared. Their conductivity was studied using complex impedance method. The most conducting foils were composed of ca. 40 wt.% of PVA, 25–30 wt.% of KOH, and 30–35 wt.% of water. Typical conductivity of such foils reached the level of nearly 10−3 Ω−1cm−1 at room temperature. Temperature dependence of the conductivity was found to be in agreement with the Arrhenius expression with the activation energy of the order of 28–22 kJmol−1, depending on the electrolytes composition. The electrochemical stability window at the metal/electrolyte interface is of 1.5 V for stainless steel and nickel, and of 1.7 and 2.75 V for platinum and gold, respectively. Such alkaline electrolytes are interesting from the point of view of their potential application in all-solid rechargeable alkaline batteries as well as in small electrochemical devices, such as chemical capacitors, electrochromic or photogalvanic devices.
physica status solidi (b), 2010
ABSTRACT Topographical and electronic and properties of step bunched Si(111), prepared by electro... more ABSTRACT Topographical and electronic and properties of step bunched Si(111), prepared by electrochemical processing in alkaline solution, are analyzed. Tapping mode atomic force microscopy (TM AFM) analysis shows that one bunched step consists of about 15 atomic steps (each 0.314 nm in height) and that the (111) oriented terraces have widths that range from 150 to 250 nm. Scanning tunneling microscopy (STM) experiments show a corrugation of the (111) terraces with an rms roughness of 0.5–0.8 nm, correlated with etch pits in alkaline solution. Low energy electron diffraction (LEED) data show a splitting of the (10) and (01) spot from which a minimum terrace width of 4.8 nm have been calculated in good agreement with the TM AFM data. Kelvin probe force microscopy (KPFM) experiments show a decrease of the contact potential difference (CPD) at and near the edges of steps indicating a more negatively charged surface area. Synchrotron radiation photoelectron spectroscopy (SRPES) on electrochemically and purely chemically prepared step bunched surfaces is compared. From the Si 2p core level shift, and, in particular, from the onset of the valence band emission, an accumulation layer-type shift is observed on the electrochemically prepared sample that is absent for chemical preparation. The move of the Fermi level toward the conduction band minimum of the electrochemically conditioned samples is interpreted by H incorporation and discussed by a doping model that involves the mechanism of hydrogen evolution.
Thin Solid Films, 2005
Investigations on how to replace the toxic KCN etching for the removal of Cu–S phases during the ... more Investigations on how to replace the toxic KCN etching for the removal of Cu–S phases during the preparation of CuInS2 (CIS) absorber layers by electrochemical procedures are presented. Starting from a simple anodic treatment in V2+/V3+ electrolyte, a more complex photoelectrochemical technique is developed which consists of different consecutive etching steps for the dissolution of the predominant CuS and for
The Journal of Physical Chemistry C, 2013
ABSTRACT Oxidation and dissolution phenomena of Si(111) in alkaline electrolyte are investigated ... more ABSTRACT Oxidation and dissolution phenomena of Si(111) in alkaline electrolyte are investigated by a combination of photoelectrochemistry, scanning probe microscopy (SPM), transmission electron microscopy (TEM) and in-system synchrotron radiation photoelectron spectroscopy (SRPES). The surface topography in the initial anodic potential regime shows the formation of mesoscale pores with widths in the range 300–500 nm and partial surface oxidation. The surface chemistry assessment by SRPES shows patchy silicon oxide growth, suboxides, and remnants of the former hydrogen terminated surface areas. The use of the obtained self-organized nanostructures for application in nanoemitter photocatalytic solar cells is discussed. The necessary requirements regarding the total surface area of electrocatalysts needed to sustain the current density due to light-induced excess minority carriers in conjunction with the exchange current density of the considered heterogeneous catalysts is discussed.
The Journal of Physical Chemistry C, 2014
Physica Scripta, 2009
Step-bunched Si surfaces with step heights of ~3 nm have been prepared as substrates for immobili... more Step-bunched Si surfaces with step heights of ~3 nm have been prepared as substrates for immobilization of the enzyme reverse transcriptase of the avian myeloblastosis virus. Tapping mode atomic force microscopy has been used for imaging. Calibration experiments using the carrier solution without the enzyme show the preservation of the surface without organic contamination. Upon enzyme deposition, two specific shapes
Journal of Solid State Electrochemistry, 2009
Photoelectrochemically prepared nanotopographies on semiconductors are used for realization of na... more Photoelectrochemically prepared nanotopographies on semiconductors are used for realization of nanoemitter solar devices that are active in the photovoltaic and the photoelectrocatalytic mode. The development of solar devices by a nonlinear electrochemical process and combined chemical/electrochemical metal deposition is described. Based on this low-temperature scalable approach, first efficiencies of 7.3% in the photovoltaic mode are reported for the photoelectrochemical solar cell n-Si/SiO 2 /Pt/I 3 − -I − . With p-Si/Pt nanocomposite structures, light-induced H 2 evolution is achieved. The surface chemistry and morphology is analyzed by photoelectron spectroscopy (PES), Fourier transform infrared spectroscopy, and high-resolution scanning electron microscopy. The operational principle of Pt-based nanoemitter solar devices that use silicon single crystal absorbers is analyzed by Mott-Schottky plots, chronoamperometric profiles, and PES. Related to simultaneous oxide formation during Pt deposition, evidence for the formation of a metal-oxide-semiconductor junction is obtained that explains the observed electronic behavior.
Journal of Materials Chemistry, 2012
An electrochemically functionalized surface of p-type silicon was used as a nanostructured materi... more An electrochemically functionalized surface of p-type silicon was used as a nanostructured material for immobilization and activation of a redox metalloprotein. A protocol resulting in the stable enzyme adsorption and utilization was applied to Trametes versicolor laccase (TvL), the ''blue'' coppercontaining oxidase enzyme, a model bio-electrocatalyst for oxygen reduction. The obtained system was tested as a photocatalytic electrode for oxygen sensing through its electroreduction at copper ionic active sites following illumination with visible light. Processes related to the photoexcitation and charge separation occur within the semiconductor (SC) material. Direct, rather than mediated by 2,2 0azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), electron transfers from the semiconductor to the enzyme were observed. The topography of the p-Si substrate was assessed by transmission electron microscopy (TEM) and tapping mode atomic force microscopy (TM AFM) methods. The electronic properties of the systems were tested using synchrotron radiation photoelectron spectroscopy (SRPES). The nature of the biomolecule immobilization was studied by TM AFM.
Journal of The Electrochemical Society, 2009
ABSTRACT Ir nanoislands were electrodeposited from chloride solutions on n type Si 111 surfaces. ... more ABSTRACT Ir nanoislands were electrodeposited from chloride solutions on n type Si 111 surfaces. The conditioned surface was investigated by electrochemical capacitance measurements, ex situ atomic force microscopy, high resolution transmission electron microscopy, and in system synchrotron radiation photoelectron spectroscopy SRPES . The growth of metal particles was accompanied by the formation of an ultrathin oxide layer, conforming to nanodimensioned metal oxide semiconductor MOS junctions. SRPES Si core level spectra obtained with surface sensitive excitation energies show the presence of a SiO2 signal with 30 40 of the oxide signal contribution arising from intermediate oxidation states Si , Si2 , and Si3 . The valence band spectrum reveals that the Fermi level of silicon is pinned at the gap states of the Si SiO2 interface at 0.6 eV above the valence band, driving the semiconductor under depletion. The presence of metal particles induces a lateral modulation of the interfacial electric field by the formation of nanoscaled MOS junctions with a Schottky barrier of 0.84 eV, as assumed by extrapolating the behavior of full covered solid state MOS junctions
Journal of Electroanalytical Chemistry, 2011
The development of hybrid biological – inorganic semiconductor structures towards biophotoelectro... more The development of hybrid biological – inorganic semiconductor structures towards biophotoelectrocatalytically active systems is described. The aspect of immobilization is analyzed using the heterodimer reverse transcriptase of the avian myeloblastosis virus (RT AMV), deposited onto step-bunched Si(111) and the defect-rich layered semiconductor MoTe2. Surface site specific adsorption is observed in high-resolution tapping mode atomic force microscopy (TM-AFM) measurements of AMV