J. Augustynski - Academia.edu (original) (raw)
Papers by J. Augustynski
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1979
Adsorption properties of futile modification of TiO2 (used in the powder form) have been previous... more Adsorption properties of futile modification of TiO2 (used in the powder form) have been previously investigated [1] by means of acid--base potentiometric titrations. Those measurements have allowed the following, decreasing, order of adsorbabilities of inorganic anions to be established: C1--~ C10~ -~ NOT > i-.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1982
The Journal of Physical Chemistry B, 1997
The effect of the roughening of the silver surface upon photoemission observed in the presence of... more The effect of the roughening of the silver surface upon photoemission observed in the presence of two different scavengers dissolved in an aqueous solution, CO 2 and NO 3 -ions, was re-examined. The quantum yield of the photocurrent exhibits a sharp maximum at 370-380 nm in the frequency range of surface plasmons on silver. These photoyields were strongly affected by the extent of the roughening of the Ag surface and reached an unusually large value of 0.05 electron per incident photon. Electrochemical oxidation/reduction roughening performed in the presence of Cl -, Br -, and ClO 4 -ions, similar to that employed in enhanced Raman scattering (SERS) experiments, affected the maximum of the photocurrent and in some cases also its onset potential. Photocurrents arising at potentials more negative than the potential of zero charge (pzc) of silver were principally influenced by changing morphology of the surface resulting from more or less deep roughening performed in different solutions. On the other hand, the photoelectrochemical behavior of silver at potentials positive with respect to the pzc was clearly affected by the specific adsorption of anions of the supporting electrolyte. It was, in particular, the Branion that caused in this potential region the strongest enhancement of the photocurrent, associated with the reduction of scavengers and led to an apparent positive shift of the onset potential. The role played by the specifically adsorbed anions is interpreted in terms of slowing down the reverse reactions of solvated electrons and of reaction intermediates (such as, for example, the NO 3 2anion) returning to the electrode.
Journal of the American Chemical Society, 1999
The reduction of cyanide to form methane, ammonia, and methylamine, which occurs in biological sy... more The reduction of cyanide to form methane, ammonia, and methylamine, which occurs in biological systems catalyzed by molybdenum nitrogenase, 1 the enzyme which catalyzes nitrogen reduction to ammonia, has never been reproduced until now in artificial systems. However, in an attempt to mimic the biological systems, Hughes et al. 2 succeeded in synthesizing Mo-containing complexes able to coordinate cyanide and to convert it electrochemically but only to the aminocarbyne ligand (ModCNH 2 ), a supposed intermediate in the HCN reduction by nitrogenase. In fact, despite a considerable amount of work devoted to catalytic activation of cyanide in nonbiological systems, no reports exist on its complete conversion to methane even at high temperatures and at elevated pressures. 3,4 Herein we report, for the first time, the electrochemical reduction of cyanide in aqueous solution occurring at nickel, copper, and silver electrodes. In particular, electrolyses of a NaCN solution of pH 6 (0.035 M NaCN, 1 M NaClO 4 , 0.2 M phosphate buffer) on a Ni cathode 5 led to the formation of large amounts of methylamine, ammonia, and methane consistent with reactions 1 and 2. 6 Note that the final products of cyanide reduction, CH 4 and NH 3 , are also reactants in an industrial synthesis of HCN. 7 The standard redox potential, E°, calculated with ∆G°values 8 for the gaseous reactants and products of reaction 1, is 0.238 V, while in the case of reaction 2, E o ) 0.331 V. These values are much more positive than the observed onset of HCN reduction that (as discussed below) appears to be closely related to the potential at which hydrogen is actually formed at the electrode surface. The highest faradaic efficiency, exceeding 70%, was observed for a Ni cathode polarized at -1.4 V vs AgCl/Ag/Cl -, i.e., ca. 1 V below E°for reaction 1, where the amount of CH 3 NH 2 formed was ca. 3.7 times larger than that of NH 3 . 9 HPLC analyses of the solutions collected at the end (normally after 1 h) of electrolyses in the cathodic compartment were performed following essentially the method described by Krause et al. 10 Hydrocarbons, including methane and minor amounts of ethylene and ethane, in the effluent gas from the cathodic compartment of the cell were monitored by gas chromatography 11 and, in addition, by GC-mass spectrometry ). The amount of the reduction products followed the increase of the cathodic current down to -1.4 V and then decreased in the potential region corresponding to the reduction of water. At -1.7 V, the faradaic efficiency dropped to ca. Mills, P.; Celio, H.; Belyanski, M.; Trenary, M. 252-253) report the reduction of cyanide on a platinum oxide catalyst, in dilute aqueous sulphuric acid, under atmospheric pressure of hydrogen, yielding methylamine. Small amounts of CH4 and NH3 were detected during thermal decomposition of K3Co(CN)5L (L ) CN -, NO2 -, N3 -, NO) complexes (Yuan, J.; Xin, X.; Dai, A. Thermochim. Acta 1988, 130, 77-85). On the other hand, CH3NH2 and NH3 were formed on boiling alkaline solutions of KCN or K4[Fe(CN)6] in the presence of Raney nickel (Tanabe, Y.; Miyantani, J. Bunseki Kagaku 1978, 27, 123-125).
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998
Pyridine added to a solution containing scavengers of photoelectrons emitted from silver (N20, CO... more Pyridine added to a solution containing scavengers of photoelectrons emitted from silver (N20, COz) causes a strong decrease in the measured photocurrent or even its complete suppression for concentrations of pyridine exceeding 0.1 M. Such behaviour, which remains in apparent contradiction to the effect of deposited pyridine on photoemission from silver in vacuum, is due to the fact that pyridine itself acts as an acceptor of the emitted photoelectrons. As the anion radical formed undergoes reoxidation (back electron transfer) at the silver surface, this process leads to a decrease in the net photocurrent which is dependent on the concentration ratio of the two competing acceptors (i.e. pyridine and N20). The observation that pyridine (adsorbed on silver and in solution) sustains a reversible electron transfer, along with the previous observation that photoemission from a roughened Ag electrode into an aqueous solution extends to at least 650 nm, provides a possible interpretation of the surface-enhanced Raman spectroscopy effect for pyridine, which involves both electromagnetic and charge-transfer mechanisms.
Chemischer Informationsdienst, 1975
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1984
X-ray photoelectron spectroscopic measurements on the state of Ir and O species in electrochemica... more X-ray photoelectron spectroscopic measurements on the state of Ir and O species in electrochemically and thermally formed iridium oxide films are reported. The electrochemically formed films were grown to three thicknesses by means of potential cycling. The monolayer oxide film which exhibits electrochemical irreversibility in its formation and reduction already causes a change of electronic state of the Ir substrate surface atoms corresponding to formation of an Ir(OH)4 species. However, if any electrochemically reversible, thick film oxide, 100 × a monolayer is formed, it behaves like bulk IrO 2 powder with regard to 4f electron shell binding energies. The state of O (ls) is also different in this material from that in thinner oxide films, and contains clearly distinguishable ionic 0 2-rather than OH-, bound water, or adsorbed 02, although the latter type of species is also present. Appreciable SO 2-ion incorporation or irreversible adsorption can also be detected. No difference in the oxidation state of Ir can be detected on (i.e., over -
Chemischer Informationsdienst, 1973
The Journal of Physical Chemistry, 1993
Relatively thick (in the range of 50 pm) electrochemically grown polyaniline films, with and with... more Relatively thick (in the range of 50 pm) electrochemically grown polyaniline films, with and without incorporated platinum microparticles, have been characterized by means of ac impedance measurements. In particular, resistance changes for both kinds of films were followed in situ (in 1 M aqueous H2S04 solution) as a function of potential. Rather unexpectedly, the rate of redox conversion of such polyaniline films is found to increase significantly in the presence of less than 100 pg cm-2 of electrodeposited metal particles dispersed inside the polymer layer.
Journal of Materials Research, 2010
Journal of Molecular Catalysis, 1984
X-ray photoelectron spectroscopy (XPS), electron microscopy and cyclic voltammetry have been used... more X-ray photoelectron spectroscopy (XPS), electron microscopy and cyclic voltammetry have been used to characterize the behaviour of two differently prepared platinum catalysts supported on TiOz (anatase). One of these two kinds of catalysts, consisting of Pt deposits obtained by thermal hydrolytic decomposition of aqueous H*PtCl, onto Ti-supported TiOz films and subsequently reduced in argon at 550 "C, has been shown to exhibit a series of anomalous properties denoting the existence of strong metalsupport interaction (SMSI).
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989
Solar Hydrogen and Nanotechnology, 2006
We report here some progress on the development of materials for photoelectrochemical water split... more We report here some progress on the development of materials for photoelectrochemical water splitting with respect to solar hydrogen generation -a CO 2 neutral, clean energy technology ( ).
Energy Procedia, 2012
Silver nanoparticles deposited on FTO conductive glass substrate have been incorporated within n-... more Silver nanoparticles deposited on FTO conductive glass substrate have been incorporated within n-type WO 3 films formed by a sol-gel method. A large enhancement in water splitting photocurrents under AM1.5 visible light irradiation for the WO 3 photoanode with embedded Ag nanoparticles was observed. The ability of Ag nanoparticle arrays on FTO to generate localized surface plasmons under visible wavelengths in the presence of the WO 3 over-layer was confirmed by scanning near-field optical microscopy (SNOM) measurements.
Nature Photonics, 2012
Photoelectrochemical water-splitting devices, which use solar energy to convert water into hydrog... more Photoelectrochemical water-splitting devices, which use solar energy to convert water into hydrogen and oxygen, have been investigated for decades. Multijunction designs are most efficient, as they can absorb enough solar energy and provide sufficient free energy for water cleavage. However, a balance exists between device complexity, cost and efficiency. Water splitters fabricated using triple-junction amorphous silicon 1,2 or III-V 3 semiconductors have demonstrated reasonable efficiencies, but at high cost and high device complexity. Simpler approaches using oxide-based semiconductors in a dual-absorber tandem approach 4,5 have reported solar-to-hydrogen (STH) conversion efficiencies only up to 0. 3% (ref. 4). Here, we present a device based on an oxide photoanode and a dye-sensitized solar cell, which performs unassisted water splitting with an efficiency of up to 3.1% STH. The design relies on carefully selected redox mediators for the dye-sensitized solar cell 6,7 and surface passivation techniques 8 and catalysts 9 for the oxidebased photoanodes.
Journal of Solid State Electrochemistry, 2004
The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tu... more The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tungstic hexaethoxide precursors with the addition of an organic stabiliser via a sol-gel method is reported. These films have been structurally characterised and both the film morphology and crystalline composition of the films were found to be significantly dependent on the temperature at which the films were annealed and upon the choice of precursor. Films annealed at lower temperatures consisted of amorphous and hexagonal tungsten trioxide, whereas films annealed above 500°C comprised solely of monoclinic WO 3 . The electrochromic activity of the films was found to be equally dependent on method of preparation, and both the composition and the structure of the WO 3 films were shown to clearly influence the colouration efficiency of the films.
Journal of The Electrochemical Society, 1977
The preparation of novel semiconducting electrodes, based on polycrystalline titanium dioxide hav... more The preparation of novel semiconducting electrodes, based on polycrystalline titanium dioxide having exceptionally good current-voltage characteristics, is reported. These electrodes are formed by mixed oxide TiOâ-M/sub x/O/sub y/ deposits on metallic titanium substrates, M being a divalent or trivalent element. The mixed oxide coatings were prepared by spraying a solution containing, for example, chlorides of both metals (elements) entering the
Journal of Electroanalytical Chemistry, 2011
Spectroelectrochemical studies have been undertaken to explain changes in the capacitance of meso... more Spectroelectrochemical studies have been undertaken to explain changes in the capacitance of mesoporous semiconducting WO 3 films, deposited on FTO conductive glass substrates, and immersed in aqueous acidic solutions. The capacitance of the mesoporous WO 3 films, determined in EIS measurements, decreased over three orders of magnitude with an exponential decay while the electrode potential was increased from +0.3 to 1 V vs. RHE. The results show that within this potential range the capacitance is related to the specific properties of the mesoporous semiconductor|solution interphase. The process of the accumulation layer formation is accompanied by hydrogen intercalation at lower potentials. The comparison of Raman and SERS experiments, both performed under the potential control, points out that the hydrogen insertion takes place first only in the outermost sphere and then in the nanoparticle core and that these processes are clearly separated on the potential scale. From the practical point of view, these results suggest that the capacitance (or dc current) may be used for the real (active) surface determination.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1979
Adsorption properties of futile modification of TiO2 (used in the powder form) have been previous... more Adsorption properties of futile modification of TiO2 (used in the powder form) have been previously investigated [1] by means of acid--base potentiometric titrations. Those measurements have allowed the following, decreasing, order of adsorbabilities of inorganic anions to be established: C1--~ C10~ -~ NOT > i-.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1982
The Journal of Physical Chemistry B, 1997
The effect of the roughening of the silver surface upon photoemission observed in the presence of... more The effect of the roughening of the silver surface upon photoemission observed in the presence of two different scavengers dissolved in an aqueous solution, CO 2 and NO 3 -ions, was re-examined. The quantum yield of the photocurrent exhibits a sharp maximum at 370-380 nm in the frequency range of surface plasmons on silver. These photoyields were strongly affected by the extent of the roughening of the Ag surface and reached an unusually large value of 0.05 electron per incident photon. Electrochemical oxidation/reduction roughening performed in the presence of Cl -, Br -, and ClO 4 -ions, similar to that employed in enhanced Raman scattering (SERS) experiments, affected the maximum of the photocurrent and in some cases also its onset potential. Photocurrents arising at potentials more negative than the potential of zero charge (pzc) of silver were principally influenced by changing morphology of the surface resulting from more or less deep roughening performed in different solutions. On the other hand, the photoelectrochemical behavior of silver at potentials positive with respect to the pzc was clearly affected by the specific adsorption of anions of the supporting electrolyte. It was, in particular, the Branion that caused in this potential region the strongest enhancement of the photocurrent, associated with the reduction of scavengers and led to an apparent positive shift of the onset potential. The role played by the specifically adsorbed anions is interpreted in terms of slowing down the reverse reactions of solvated electrons and of reaction intermediates (such as, for example, the NO 3 2anion) returning to the electrode.
Journal of the American Chemical Society, 1999
The reduction of cyanide to form methane, ammonia, and methylamine, which occurs in biological sy... more The reduction of cyanide to form methane, ammonia, and methylamine, which occurs in biological systems catalyzed by molybdenum nitrogenase, 1 the enzyme which catalyzes nitrogen reduction to ammonia, has never been reproduced until now in artificial systems. However, in an attempt to mimic the biological systems, Hughes et al. 2 succeeded in synthesizing Mo-containing complexes able to coordinate cyanide and to convert it electrochemically but only to the aminocarbyne ligand (ModCNH 2 ), a supposed intermediate in the HCN reduction by nitrogenase. In fact, despite a considerable amount of work devoted to catalytic activation of cyanide in nonbiological systems, no reports exist on its complete conversion to methane even at high temperatures and at elevated pressures. 3,4 Herein we report, for the first time, the electrochemical reduction of cyanide in aqueous solution occurring at nickel, copper, and silver electrodes. In particular, electrolyses of a NaCN solution of pH 6 (0.035 M NaCN, 1 M NaClO 4 , 0.2 M phosphate buffer) on a Ni cathode 5 led to the formation of large amounts of methylamine, ammonia, and methane consistent with reactions 1 and 2. 6 Note that the final products of cyanide reduction, CH 4 and NH 3 , are also reactants in an industrial synthesis of HCN. 7 The standard redox potential, E°, calculated with ∆G°values 8 for the gaseous reactants and products of reaction 1, is 0.238 V, while in the case of reaction 2, E o ) 0.331 V. These values are much more positive than the observed onset of HCN reduction that (as discussed below) appears to be closely related to the potential at which hydrogen is actually formed at the electrode surface. The highest faradaic efficiency, exceeding 70%, was observed for a Ni cathode polarized at -1.4 V vs AgCl/Ag/Cl -, i.e., ca. 1 V below E°for reaction 1, where the amount of CH 3 NH 2 formed was ca. 3.7 times larger than that of NH 3 . 9 HPLC analyses of the solutions collected at the end (normally after 1 h) of electrolyses in the cathodic compartment were performed following essentially the method described by Krause et al. 10 Hydrocarbons, including methane and minor amounts of ethylene and ethane, in the effluent gas from the cathodic compartment of the cell were monitored by gas chromatography 11 and, in addition, by GC-mass spectrometry ). The amount of the reduction products followed the increase of the cathodic current down to -1.4 V and then decreased in the potential region corresponding to the reduction of water. At -1.7 V, the faradaic efficiency dropped to ca. Mills, P.; Celio, H.; Belyanski, M.; Trenary, M. 252-253) report the reduction of cyanide on a platinum oxide catalyst, in dilute aqueous sulphuric acid, under atmospheric pressure of hydrogen, yielding methylamine. Small amounts of CH4 and NH3 were detected during thermal decomposition of K3Co(CN)5L (L ) CN -, NO2 -, N3 -, NO) complexes (Yuan, J.; Xin, X.; Dai, A. Thermochim. Acta 1988, 130, 77-85). On the other hand, CH3NH2 and NH3 were formed on boiling alkaline solutions of KCN or K4[Fe(CN)6] in the presence of Raney nickel (Tanabe, Y.; Miyantani, J. Bunseki Kagaku 1978, 27, 123-125).
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998
Pyridine added to a solution containing scavengers of photoelectrons emitted from silver (N20, CO... more Pyridine added to a solution containing scavengers of photoelectrons emitted from silver (N20, COz) causes a strong decrease in the measured photocurrent or even its complete suppression for concentrations of pyridine exceeding 0.1 M. Such behaviour, which remains in apparent contradiction to the effect of deposited pyridine on photoemission from silver in vacuum, is due to the fact that pyridine itself acts as an acceptor of the emitted photoelectrons. As the anion radical formed undergoes reoxidation (back electron transfer) at the silver surface, this process leads to a decrease in the net photocurrent which is dependent on the concentration ratio of the two competing acceptors (i.e. pyridine and N20). The observation that pyridine (adsorbed on silver and in solution) sustains a reversible electron transfer, along with the previous observation that photoemission from a roughened Ag electrode into an aqueous solution extends to at least 650 nm, provides a possible interpretation of the surface-enhanced Raman spectroscopy effect for pyridine, which involves both electromagnetic and charge-transfer mechanisms.
Chemischer Informationsdienst, 1975
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1984
X-ray photoelectron spectroscopic measurements on the state of Ir and O species in electrochemica... more X-ray photoelectron spectroscopic measurements on the state of Ir and O species in electrochemically and thermally formed iridium oxide films are reported. The electrochemically formed films were grown to three thicknesses by means of potential cycling. The monolayer oxide film which exhibits electrochemical irreversibility in its formation and reduction already causes a change of electronic state of the Ir substrate surface atoms corresponding to formation of an Ir(OH)4 species. However, if any electrochemically reversible, thick film oxide, 100 × a monolayer is formed, it behaves like bulk IrO 2 powder with regard to 4f electron shell binding energies. The state of O (ls) is also different in this material from that in thinner oxide films, and contains clearly distinguishable ionic 0 2-rather than OH-, bound water, or adsorbed 02, although the latter type of species is also present. Appreciable SO 2-ion incorporation or irreversible adsorption can also be detected. No difference in the oxidation state of Ir can be detected on (i.e., over -
Chemischer Informationsdienst, 1973
The Journal of Physical Chemistry, 1993
Relatively thick (in the range of 50 pm) electrochemically grown polyaniline films, with and with... more Relatively thick (in the range of 50 pm) electrochemically grown polyaniline films, with and without incorporated platinum microparticles, have been characterized by means of ac impedance measurements. In particular, resistance changes for both kinds of films were followed in situ (in 1 M aqueous H2S04 solution) as a function of potential. Rather unexpectedly, the rate of redox conversion of such polyaniline films is found to increase significantly in the presence of less than 100 pg cm-2 of electrodeposited metal particles dispersed inside the polymer layer.
Journal of Materials Research, 2010
Journal of Molecular Catalysis, 1984
X-ray photoelectron spectroscopy (XPS), electron microscopy and cyclic voltammetry have been used... more X-ray photoelectron spectroscopy (XPS), electron microscopy and cyclic voltammetry have been used to characterize the behaviour of two differently prepared platinum catalysts supported on TiOz (anatase). One of these two kinds of catalysts, consisting of Pt deposits obtained by thermal hydrolytic decomposition of aqueous H*PtCl, onto Ti-supported TiOz films and subsequently reduced in argon at 550 "C, has been shown to exhibit a series of anomalous properties denoting the existence of strong metalsupport interaction (SMSI).
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989
Solar Hydrogen and Nanotechnology, 2006
We report here some progress on the development of materials for photoelectrochemical water split... more We report here some progress on the development of materials for photoelectrochemical water splitting with respect to solar hydrogen generation -a CO 2 neutral, clean energy technology ( ).
Energy Procedia, 2012
Silver nanoparticles deposited on FTO conductive glass substrate have been incorporated within n-... more Silver nanoparticles deposited on FTO conductive glass substrate have been incorporated within n-type WO 3 films formed by a sol-gel method. A large enhancement in water splitting photocurrents under AM1.5 visible light irradiation for the WO 3 photoanode with embedded Ag nanoparticles was observed. The ability of Ag nanoparticle arrays on FTO to generate localized surface plasmons under visible wavelengths in the presence of the WO 3 over-layer was confirmed by scanning near-field optical microscopy (SNOM) measurements.
Nature Photonics, 2012
Photoelectrochemical water-splitting devices, which use solar energy to convert water into hydrog... more Photoelectrochemical water-splitting devices, which use solar energy to convert water into hydrogen and oxygen, have been investigated for decades. Multijunction designs are most efficient, as they can absorb enough solar energy and provide sufficient free energy for water cleavage. However, a balance exists between device complexity, cost and efficiency. Water splitters fabricated using triple-junction amorphous silicon 1,2 or III-V 3 semiconductors have demonstrated reasonable efficiencies, but at high cost and high device complexity. Simpler approaches using oxide-based semiconductors in a dual-absorber tandem approach 4,5 have reported solar-to-hydrogen (STH) conversion efficiencies only up to 0. 3% (ref. 4). Here, we present a device based on an oxide photoanode and a dye-sensitized solar cell, which performs unassisted water splitting with an efficiency of up to 3.1% STH. The design relies on carefully selected redox mediators for the dye-sensitized solar cell 6,7 and surface passivation techniques 8 and catalysts 9 for the oxidebased photoanodes.
Journal of Solid State Electrochemistry, 2004
The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tu... more The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tungstic hexaethoxide precursors with the addition of an organic stabiliser via a sol-gel method is reported. These films have been structurally characterised and both the film morphology and crystalline composition of the films were found to be significantly dependent on the temperature at which the films were annealed and upon the choice of precursor. Films annealed at lower temperatures consisted of amorphous and hexagonal tungsten trioxide, whereas films annealed above 500°C comprised solely of monoclinic WO 3 . The electrochromic activity of the films was found to be equally dependent on method of preparation, and both the composition and the structure of the WO 3 films were shown to clearly influence the colouration efficiency of the films.
Journal of The Electrochemical Society, 1977
The preparation of novel semiconducting electrodes, based on polycrystalline titanium dioxide hav... more The preparation of novel semiconducting electrodes, based on polycrystalline titanium dioxide having exceptionally good current-voltage characteristics, is reported. These electrodes are formed by mixed oxide TiOâ-M/sub x/O/sub y/ deposits on metallic titanium substrates, M being a divalent or trivalent element. The mixed oxide coatings were prepared by spraying a solution containing, for example, chlorides of both metals (elements) entering the
Journal of Electroanalytical Chemistry, 2011
Spectroelectrochemical studies have been undertaken to explain changes in the capacitance of meso... more Spectroelectrochemical studies have been undertaken to explain changes in the capacitance of mesoporous semiconducting WO 3 films, deposited on FTO conductive glass substrates, and immersed in aqueous acidic solutions. The capacitance of the mesoporous WO 3 films, determined in EIS measurements, decreased over three orders of magnitude with an exponential decay while the electrode potential was increased from +0.3 to 1 V vs. RHE. The results show that within this potential range the capacitance is related to the specific properties of the mesoporous semiconductor|solution interphase. The process of the accumulation layer formation is accompanied by hydrogen intercalation at lower potentials. The comparison of Raman and SERS experiments, both performed under the potential control, points out that the hydrogen insertion takes place first only in the outermost sphere and then in the nanoparticle core and that these processes are clearly separated on the potential scale. From the practical point of view, these results suggest that the capacitance (or dc current) may be used for the real (active) surface determination.