Charge Transfer Rate Constant Research Articles

Electrochemical Behavior of Titanium Complexes in the KCl-KF Melt with Additions of Alkaline Earth Metal Cations

The charge transfer kinetics for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt was studied. The standard rate constants of charge transfer (ks ) for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt and the activation energy of charge transfer were calculated. Influence of strongly polarizing cations (Mg2+, Ca2+, Sr2+, and Ва2+) on the charge transfer kinetics was studied. It was determined the linear dependence of ks on the ionic potential of alkaline earth metal cations. The activation energies of charge transfer in case of strongly polarizing cations addition were found.

Mechanistic investigation of water oxidation on hematite photoanodes using intensity-modulated photocurrent spectroscopy

Exploring the nature of photogenerated intermediates during the photoelectrochemical (PEC) oxidation of water is a crucial step to enhance the performance of PEC devices. In this work, the PEC water oxidation on different hematite photoanodes, either bare or modified with cobalt-based oxygen evolution co-catalyst, has been investigated using intensity-modulated photocurrent spectroscopy (IMPS) . The phenomenological rate constants for charge transfer and recombination have been determined at different bias potentials. Their potential dependence trends have been analyzed using a mechanistic model that combines the IMPS theory and the bulk characteristic of the semiconductor. Based on this model, the nature of the formed intermediates during water oxidation is explored. It is found that water oxidation takes place through the coupling of two mobile surface intermediates and two adjacent metal sites are involved in the process. The rate constants for the trapping of the photogenerated holes and the coupling of the mobile surface intermediates have been determined. All investigated photoanodes exhibit comparable rate constants for the trapping as well as for the coupling steps. The surface modification does not significantly influence the trapping and coupling rate constants but remarkably reduces the rate constant of recombination. These results indicate that the efficiency of hematite photoanode is limited by its intrinsic properties and the surface modification has a restricted impact on the overall performance.

Electrochemical Behavior of the Ti(IV)/Ti(III) Redox Couple in the KCl–KF–K2TiF6 Melt in the Presence of Alkaline Earth Metal Cations

The standard rate constants of charge transfer for the Ti(IV)/Ti(III) redox couple in the KCl–KF(10 wt %)–K2TiF6 melt are determined by cyclic voltammetry. The activation energy of charge transfer is calculated. The influence of strongly polarizing cations Mg2+, Ca2+, Sr2+, and Ba2+ on the charge transfer kinetics in the Ti(IV)/Ti(III) redox couple when the cations are introduced into the initial melt is studied. A linear dependence of the rate constants of charge transfer on the ionic potentials of the alkaline earth metal cations is found.

Charge transfer rate constants for the carotenoid-porphyrin-C60 molecular triad dissolved in tetrahydrofuran: The spin-boson model vs the linearized semiclassical approximation.

Charge transfer rate constants were calculated for the carotenoid-porphyrin-C60 (CPC60) molecular triad dissolved in explicit tetrahydrofuran. The calculation was based on mapping the all-atom anharmonic Hamiltonian of this system onto the spin-boson Hamiltonian. The mapping was based on discretizing the spectral density from the time correlation function of the donor-acceptor potential energy gap, as obtained from all-atom molecular dynamics simulations. Different spin-boson Hamiltonians were constructed for each of the possible transitions between the three excited electronic states in two different triad conformations. The rate constants of three possible transitions were calculated via the quantum-mechanically exact Fermi's golden rule (FGR), as well as a progression of more approximate expressions that lead to the classical Marcus expression. The advantage of the spin-boson approach is that once the mapping is established, the quantum-mechanically exact FGR and the hierarchy of approximations are known in closed form. The classical Marcus charge transfer rate constants obtained with the spin-boson Hamiltonians were found to reproduce those obtained from all-atom simulations with the linearized semiclassical approximation, thereby confirming the equivalence of the two approaches for this system. Within the spin-boson Hamiltonian, we also found that the quantum-mechanically exact FGR rate constants were significantly enhanced compared to the classical Marcus theory rate constants for two out of three transitions in one of the two conformations under consideration. The results confirm that mapping to the spin-boson model can yield accurate predictions for charge transfer rate constants in a system as complex as CPC60 dissolved in tetrahydrofuran.

Polariton-Mediated Electron Transfer via Cavity Quantum Electrodynamics.

We investigate the polariton-mediated electron transfer reaction in a model system with analytic rate constant theory and direct quantum dynamical simulations. We demonstrate that the photoinduced charge transfer reaction between a bright donor state and dark acceptor state can be significantly enhanced or suppressed by coupling the molecular system to the quantized radiation field inside an optical cavity. This is because the quantum light-matter interaction can influence the effective driving force and electronic couplings between the donor state, which is the hybrid light-matter excitation, and the molecular acceptor state. Under the resonance condition between the photonic and electronic excitations, the effective driving force can be tuned by changing the light-matter coupling strength; for an off-resonant condition, the same effect can be accomplished by changing the molecule-cavity detuning. We further demonstrate that using both the electronic coupling and light-matter coupling helps to extend the effective couplings across the entire system, even for the dark state that carries a zero transition dipole. Theoretically, we find that both the counter-rotating terms and the dipole self-energy in the quantum electrodynamics Hamiltonian are important for obtaining an accurate polariton eigenspectrum as well as the polariton-mediated charge transfer rate constant, especially in the ultrastrong coupling regime.

Electric field effects on organic photovoltaic heterojunction interfaces: The model case of pentacene/C60

The applied electric field on organic heterojunction interface can significantly affect organic photovoltaic (OPV) performance. Here, to explore electric field effects on OPV heterojunction interface, the pentacene/C60 complexes with face-on and edge-on configurations were constructed as model system, based upon quantum chemistry calculations that take into account of solid polarization effects and apply density functional with optimally tuned range separation parameters, we systematically studied the electric fields effects on the complexes’ geometries, electronic structures, excitation and spectral properties, as well as the rate constants of charge transfer (CT), exciton dissociation (ED) and charge recombination (CR) processes. The electric field can effectively modify interface electronic structures and energy level alignments, and the increasing of electric field that is perpendicular to interface can increase CT energetic loss, reduce the lowest CT excitation energy and the open-circuit voltage. The introducing electric field can modulate the kinetics of electron processes at heterojunction interface.

Physical Insights into Band Bending in Pristine and Co-Pi-Modified BiVO4 Photoanodes with Dramatically Enhanced Solar Water Splitting Efficiency.

Herein, a novel method is introduced to synthesize 3D hierarchically assembled BiVO4 nanosheet photoanodes. Despite the fact that the obtained photoanodes inherit the intrinsic properties of 2D and 3D structures, they generate low photocurrent under simulated solar light at 1.0 sun. Upon modification with the cobalt-phosphate (Co-Pi) cocatalyst, the photocurrent is dramatically enhanced from 0.41 to 3.32 mA cm-2 at 1.23 VRHE. Charge-transfer kinetic studies by intensity-modulated photocurrent spectroscopy indicated that the low photocurrent response is mainly due to the high density of surface states, which pin the Fermi level and suspend the band bending. The Co-Pi loading passivates these surface states, unpins the Fermi level, and thus resumes the band bending. It also greatly enhances the rate constant of charge transfer and the overall efficiency, evincing that Co-Pi exhibits a dual function (i.e., passivation and catalysis). The current results explicitly disclose the role of the Co-Pi cocatalyst in photoelectrochemical solar water splitting on BiVO4.

Electroreduction of Holmium Chloride in the Equimolar NaCl–KCl Melt

Rare-earth metals and their alloys are widely used in various engineering fields due to their unique physical and chemical properties. To prepare rare-earth-containing coatings, data on the kinetics of electrode processes with the participation of the rare-earth metals in salt molten media should be available. These problems are poorly understood for rare-earth metals. In the present study, the kinetic parameters of the cathode reduction (transfer coefficient, heterogeneous charge transfer rate constants) of holmium ions in the equimolar NaCl–KCl melt are determined in a temperature range of 1073–1173 K in a holmium chloride concentration range of 1–10 wt % using chronopotentiometry and chronovoltammetry. The dependences of the kinetic parameters on the temperature and concentration of rare-earth metal chloride are determined. The following reduction mechanism of complex ion in the aforementioned melts is suggested: $${\text{HoCl}}_{6}^{{3 - }}$$ = $${\text{HoCl}}_{4}^{ - }$$ + 2Cl–, $${\text{HoCl}}_{4}^{ - }$$ + e → $${\text{HoCl}}_{4}^{{2 - }}.$$

Influence of light intensity on the steady-state kinetics in tungsten trioxide particulate photoanode studied by intensity-modulated photocurrent spectroscopy

Charge-carrier dynamics during photoelectrochemical (PEC) water splitting over WO3 particulate photoanode deposited on titanium sheet (Ti/WO3) was studied using intensity-modulated photocurrent spectroscopy (IMPS). The WO3 particulate film calcined at 650 °C showed high PEC performance for water oxidation to evolve O2. In linear sweep voltammetry, the photocurrent density proportionally increased with incident light intensity (I0). This means that the incident photon-to-current conversion efficiency (IPCE) of Ti/WO3 was not dependent on I0 in voltammetry. In contrast, there was no proportional relation between I0 and the photocurrent density in chronoamperometry at a constant potential, indicating that the IPCE at steady state decreased with an increase of I0. To elucidate the effect of light intensity on the steady-state IPCE, we investigated the IMPS response of Ti/WO3 photoanodes by applying a simple branching model with respect to the photogenerated holes (h+). It was found that the recombination rate constant (krec) rather than the charge transfer rate constant (kct) significantly depends on I0 at the steady-state condition. The pseudo-first-order krec increased with an increase of I0, suggesting that recombination is increased by the accumulation of photogenerated carriers during continuous PEC water oxidation. This is the reason for the decrease in the steady-state IPCE of Ti/WO3 under high-intensity light irradiation. The effects of applied potentials on the kinetic parameters (kct and krec) were also evaluated for Ti/WO3 under different I0.

Design Rules for Efficient Charge Transfer in Metal-Organic Framework Films: The Pore Size Effect.

In redox-active metal-organic frameworks (MOFs), charge transfer can occur by a redox hopping mechanism, i.e., electron hopping coupled with ion diffusion to balance electroneutrality. To elucidate the correlation between MOF structure and electron and ion diffusion, we prepared three ferrocene-doped MOF (Fc-MOF) films with different pore sizes (15-47 Å) immobilized on conductive substrates. By applying a theoretical model to the chronoamperometric responses of three Fc-MOFs, the electron and ion diffusion coefficients (De ≈ 10-12-10-7 cm2 s-1; Di ≈ 10-16-10-12 cm2 s-1) and electron- and ion-transfer rate constants (ke-hop ≈ 103-107 s-1; ki-hop ≈ 10-3-101 s-1) were quantified independently. Increasing MOF pore size led to an increase in ki-hop and a decrease in ke-hop. The overall charge-transfer rate constant, khop, increased when MOF pore size increased, confirming the ability to enhance charge-transfer rates through control of MOF pore size.

Catalyst-free fabrication of one-dimensional N-doped carbon coated TiO2 nanotube arrays by template carbonization of polydopamine for high performance electrochemical sensors

One-dimensional (1D) carbon nanomaterials have extensively explored to fabricate high performance electrochemical sensors for the merits such as high surface area and fast electron transfer kinetics. However, catalytic production of carbon nanomaterials often suffers from misinterpretations of electrochemical signals from the catalyst residue and complicated production steps. Herein, we reported a catalyst-free method to produce 1D N-doped carbon coated TiO2 nanotube arrays (N-doped C/TiO2 NTAs) by template carbonization of polydopamine nanofilm coated anodized TiO2 NTAs. The N-doped C/TiO2 NTAs possesses a uniform structure with an inner diameter for an individual nanotube of about 80 nm and a length of about 8 µm. The carbon coating is about 10 nm in thickness and is doped by nitrogen from the polydopamine precursor. The N-doped C/TiO2 NTAs electrode exhibits an extremely high electrochemical activity with the heterogeneous charge transfer rate constants k0 greater than 0.5 cm/s for Fe(CN)63−/4− redox couple. Simultaneous determination of ascorbic acid, dopamine and uric acid has been demonstrated with the linear ranges of 100–3000 μM, 5–50 μM and 0.1–150 μM, respectively and detection limits (S/N = 3) of 1.8 μM, 0.015 μM and 0.11 μM, respectively.

Analysis of Cathode Reactions of Lithium Ion Cells Using Dynamic Electrochemical Impedance

We used dynamic electrochemical impedance spectroscopy (DEIS), a method that superimposes an alternating current on a direct current during battery charging and discharging, to analyze a cathode half-cell of lithium ion batteries. Based on the analysis using instantaneous impedances derived from time-interpolation of DEIS, a comparison between the instantaneous impedances and stationary impedances that are generally measured at the equilibrium of a specific state of charge (SOC), when no direct current is flowing (SEIS), have revealed that the charge transfer resistances (Rct) obtained by DEIS during charge (extraction of lithium in a cathode) always have lower values than Rct by DEIS during discharge (insertion of lithium), while the results obtained from SEIS are almost the same during charging and discharging. Moreover, the variations of Rct vs SOC during charge depend on C-rate, whereas those during discharge are independent of the C-rate. These variations of Rct observed in charging and discharging during DEIS are attributed to the differences of rate constants for charge transfer. The underlying cause of the series of variations of Rct on DEIS can be explained using the equation of Frumkin-Butler-Volmer with Rct, which was derived previously from cyclic voltammetry as a well-known dynamic electrochemical method.

Understanding the enhanced photoelectrochemical water oxidation over Ti-doped α-Fe2O3 electrodes by electrochemical reduction pretreatment.

Water splitting using semiconductor photoelectrodes is a promising approach to solar hydrogen production. Previous studies have well-demonstrated that electrochemical reduction (ER) pretreatment of bare and Ti-doped α-Fe2O3 electrodes enhances water photooxidation efficiencies, however, the mechanism underlying this improvement remains poorly understood. In this study, this was quantitatively investigated by multiple photoelectrochemical techniques and transient absorption spectroscopy, using the doped electrodes as examples. The results reveal that the kinetics of photoholes after moving to the electrode surface can be well described by a model of surface-state mediated charge transfer and recombination. The reason for the photocurrent enhancement is attributed to a significantly increased charge transfer rate constant (kct) and a decreased surface recombination rate constant (ksr) by ER. The reason for the accelerated kct is that a new type of surface state, with a favorable energy position for water oxidation, is produced. The decreased ksr is due to the reduced electron density at the surface of the semiconductor, resulted predominately from the negatively shifted flat band potential. These findings provide new insights into the mechanism of water photooxidation and enlighten a simple way to develop more efficient electrodes.

Understanding the influence of molecular arrangements on the charge transfer properties at donor-acceptor interface: A computational study of subPC/C70 solar cell

Boron subphthalocyanine chloride (subPC)/C70 organic solar cell has been studied theoretically and experimentally. However, the electron transfer and charge recombination at the interface between subPC and C70 is rarely studied. It is still an open question how molecular arrangements and orientations influence its charge transfer properties at the subPC/C70 interface. Therefore, in this work, by utilizing reliable density functional theory and time-dependent density functional theory, we have modelled six possible bi-molecular systems to simulate molecular arrangements at the interface, and calculated charge transfer and charge recombination rate constants between multiple excited states in gas phase. The results indicate that the exciton life time at the interface ranges from 70.9 fs to 7.81 ps. The outcomes also suggest the charge separation process occurs dominantly in the umbrella configurations in which C70 is in the concave of subPC, and almost is unlikely to happen in other configurations. The findings propose that it would be a promising way to improve the performance of subPC/C70 solar cell by increasing the ratio of umbrella configurations at the interface during fabricating processes.

Tuning of reduced graphene oxide thin film as an efficient electron conductive interlayer in a proven heterojunction photoanode for solar-driven photoelectrochemical water splitting

Although bismuth vanadate (BiVO4) has shown excellent photoelectrochemical (PEC) properties and is a good candidate of photoanode materials, the solar-driven PEC water splitting performance is still remained below its full potential due to the fast recombination and sluggish charge mobility of photogenerated charge carriers. Previously, we have communicated a proven Type II staggered vanadium pentoxide (V2O5)/BiVO4 heterojunction photoanode that could improve the photocurrent density. This study aimed to examine the effect of introducing an rGO thin film as an efficient electron conductive interlayer in a proven V2O5/BiVO4 heterojunction photoanode, and subsequently tuning the rGO film thickness in achieving the optimum PEC performance. The resultant ternary photoanode structure of V2O5/rGO/BiVO4 was characterised by using field emission-scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), UV–vis spectroscopy, X-ray diffractometer (XRD), Raman spectroscopy and photoluminescence (PL) measurements. Results showed that the interlayer rGO thin film arising from the sequential drop cast and electrochemical reduction of 320 μL ultrasonicated GO solution resulted in the optimal photocurrent density of 2.1 mA/cm2 at 1.5 V vs. Ag/AgCl. Furthermore, the chemical physics surrounding the photogenerated charge carrier transfer for heterojunction V2O5/BiVO4 was validated for the structure with and without the rGO interlayer. In particular, the electrochemical impedance spectroscopy (EIS) was used to measure multiple resistances at the FTO/semiconductor, semiconductor/semiconductor and semiconductor/electrolyte interfaces. Additionally, the charge transfer (Kt) and recombination (Kr) rate constants for the heterojunction V2O5/BiVO4 with the rGO interlayer were quantified using intensity modulated photocurrent spectroscopy (IMPS). Finally, the PEC H2 evolution rate from the ternary V2O5/rGO/BiVO4 photoanode was measured to be 32.7 μ mol/hr, which was about 3-fold higher than the bare V2O5/BiVO4 heterojunction photoanode.

Heteroatom-doped carbon nanofilm embedded in highly ordered TiO2 nanotube arrays by thermal nitriding with enhanced electrochemical activity

We presented a facile strategy to fabricate highly ordered one-dimensional nitrogen-doped carbon nanofilm embedded in TiO2 nanotube arrays (N–C/TiO2 NTAs) by catalyst-free carbonization on the template of anodized TiO2 NTAs and thermal nitriding. The N–C/TiO2 NTAs exhibit an ideal Nernst behavior towards [Fe(CN)6]3-/4- redox couple with the heterogeneous charge transfer rate constants greater than 0.5 cm/s, indicating an extremely high electrochemical activity. Simultaneous determination of ascorbic acid and uric acid has been demonstrated with the linear ranges of 100–3000 μM, and 1.0–150 μM, respectively and detection limits (S/N = 3) of 8.0 μM, and 0.10 μM, respectively.

Electrocatalytic oxidation and amperometric determination of hydrazine using a carbon paste electrode modified with β-nickel hydroxide nanoplatelets.

β-Nickel hydroxide nanoplatelets (NPs) were synthesized and used as a modifier on a carbon paste electrode (CPE) for the detection of hydrazine. Synthesis is based on a one-step hydrothermal method using L-arginine that acts as an agent to adjust the pH value and to shape the NPs. They were characterized by field emission scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The composition of the modified electrode was optimized by changing the amount of NPs. Best results were achieved using a 10:70:20 weight ratio for nanoparticles, graphite and mineral oil (the binder). The electrochemical properties of the modified CPE were studied by cyclic voltammetry. The surface coverage of the NPs, the electron transfer coefficient and the charge transfer rate constant were calculated. The diffusion coefficient of hydrazine is 1.56 × 10-5cm2s-1. An amperometric method was worked out that has the following figures of merit: (a) A working applied potential of 500mV (vs. Ag/AgCl reference electrode), (b) a linear range that extends from 1 to 1300μmolL-1, (c) a 0.28μmolL-1 detection limit, (d) a relative standard deviation of 1.3% (for n = 3 at a level of 5μmolL-1), and (d) a sensitivity of 1.33μAμmol-1Lcm-2. The performance of the sensor is compared to other nickel-based sensors for hydrazine. The sensor was successfully used to quantify hydrazine in spiked tap water samples, and the recoveries were 97 ± 2.3% (n = 3). Graphical abstract Schematic presentation of hydrazine electrocatalytic oxidation on NP.CPE*. *NP-CPE (β-nickel hydroxide nanoplatelet modified carbon paste electrode).

Enhancing a Novel Robust Multicomposite Materials Platform for Glucose Biosensors

AbstractAn effective, stable enzymatic glucose biosensor was fabricated on a glassy carbon electrode (GCE) surface using simple multicomposite materials (MCM): a solution of prepared poly(diallyldimethylammonium chloride)‐capped gold nanoparticles‐nickel ferrite particles‐carbon nanotubes‐chitosan (PDDA‐AuNPs‐NiFe2O4‐CNTs‐CHIT), electropolymerization of poly(o‐phenylenediamine) (PoPD) and immobilization of glucose oxidase (GOx). Biocompatibility and synergy of the MCM enhanced the immobilization and the reaction of GOx and as well as the electron transfer from an oxidation reaction of hydrogen peroxide in the system. The NiFe2O4 was synthesized by co‐precipitation and calcined at 700 °C. Characterization was carried out by field emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) which presented both tetrahedral and octahedral metal stretching with a cubic NiFe2O4 crystal phase. The GOx/PoPD/MCM/GCE yielded a 0.77 s−1 charge transfer rate constant (Ks), a 2.28×10−6 cm2 s−1 diffusion coefficient value (D), a 0.21 mm2 electroactive surface area (Ae) and a 1.93×10−8 mol cm−2 surface concentration ( ) as determined by cyclic voltammetry. The modified electrode showed a durable operation time (n=97, more than 50 % I), repeatability (%RSD=0.38, n=10), reproducibility (%RSD=1.60, n=10), high sensitivity (853.07 μA mM−1 cm−2), selectivity without effects of electroactive species (aspirin, uric acid, caffeine, cholesterol, ascorbic acid and dopamine) and two linear ranges from 0.5 to 10 μM (R2=0.998) and 10 to 15,000 μM (R2=0.991) with a low detection limit (0.35 μM, S/N=3). Its Michaelis‐Menten constant (Km) was calculated as 93.51 μM with 46.30 μA maximum current (Imax). This proposed simple method was successfully applied for glucose determination in human blood samples.

(Invited) Photoelectrochemistry of Semiconducting Oxide Materials for Solar Water Splitting

There is a large family of binary, ternary, quaternary, etc. metal oxides that exhibit semiconducting properties, which makes them possible candidates to be applied in solar water splitting. With the recent advances in the controlled and economical synthesis of a large variety of metal oxides and their physical properties, new efforts in the photoelectrochemical characterization of such materials has become an important focus of research in the solar water splitting community.1,2 Although photoelectrochemical water splitting is an attractive method to convert solar energy to storable chemical energy in the form of hydrogen, the materials requirements to achieve this efficiently are very challenging. The semiconducting material needs to absorb sunlight efficiently, must to be capable of reducing and/or oxidizing water, and has to be stable under illumination under current flow in an aqueous electrolyte solution. In particular, for small bandgap semiconductors, stability is often an issue. In addition, the water reduction and oxidation reactions need to occur fast, in order to effectively compete with recombination or surface degradation processes. The kinetic rate constants for charge transfer and surface recombination therefore are important parameters, but these are difficult to obtain from steady-state measurements. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful option to study the carrier dynamics in a photoelectrochemical cell. The frequency-dependent photocurrent admittance corresponds to the frequency-dependent external quantum efficiency, and time constants for charge transfer and surface recombination can be determined using a simple model, depending on the complexity of the system under study.3 We have used IMPS on a variety of systems including WO3, p-CuBi2O4 and WO3-BiVO4 heterojunctions, in order to elucidate the rate determining steps in the charge carrier dynamics. For CuBi2O4 photocathodes, an unfavorable balance between the rate constants for charge transfer and surface recombination is found to limit the conversion efficiency.4 On the other hand, IMPS analysis of screen-printed WO3 photoanodes shows that the recombination rate constant is significantly smaller than the charge transfer rate constant; however, the film thickness plays an important role in collection efficiency.5 Recent results on WO3-BiVO4 heterojunctions, CuWO4, and electrocatalyzed Sn-doped Fe2O3 photoanodes are also discussed. References “Solar Hydrogen Generation: Toward a Renewable Energy Future”. K. Rajeshwar, R. McConnell and S. Licht, Editors, Kluwer Academic, New York (2008).“Solution combustion synthesis of oxide semiconductors for solar energy conversion and environmental remediation”. K. Rajeshwar and N. R. de Tacconi, Chem. Soc. Rev. 38(7) 1984-1998 (2009).“Photoelectrochemical Water Splitting at Semiconductor Electrodes: Fundamental Problems and New Perspectives”. L. M. Peter and K. G. Upul Wijayantha, ChemPhysChem, 15, 1983–1995 (2014).“Charge Transfer and Recombination Dynamics at Inkjet-Printed CuBi2O4 Electrodes for Photoelectrochemical Water Splitting”. Ingrid Rodríguez-Gutiérrez, Rodrigo García-Rodríguez, Manuel Rodríguez-Pérez, AlbertoVega-Poot, Geonel Rodríguez Gattorno, Bruce A. Parkinson, and Gerko Oskam. J. Phys. Chem. C, 122, 27169−27179 (2018).“Charge Transfer and Recombination Kinetics at WO3 for Photoelectrochemical Water Oxidation”. Manuel Rodríguez-Pérez, Ingrid Rodríguez-Gutiérrez, Alberto Vega-Poot, Rodrigo García-Rodríguez, Geonel Rodríguez-Gattorno, Gerko Oskam. Electrochim. Acta, 258, 900-908 (2017).

(Invited) Analysis of Charge Transfer Reactions with Semiconductor Ultramicroelectrodes

This presentation will detail our latest advancements utilizing semiconductor ultramicroelectrodes (SUMEs) as platforms to study semiconductor/liquid interfaces. Specifically, we will show the accurate, quantitative measurement of heterogeneous charge transfer rate constants with n-Si, n-GaP, and n-GaN SUMEs immersed in non-aqueous electrolytes. The intent is to develop methodologies that test the extent that classical Marcus theory describes charge transfer at semiconductor/liquid interfaces. The presented data will show that SUMEs offer the unique possibility of making measurements either in depletion or in accumulation conditions. Additional data will be presented that highlighted the response characteristics of SUME arrays under illumination, highlighting an alternative design motif for PEC photoelectrodes.