Interfacial Electron Transfer Processes Research Articles

Deciphering the Role of p-Type ZnCo2O4 Semiconductor Nanoflakes for Selective Enhancement of Voltammetric Responses Toward Redox Species System: Interfacial Electron-Transfer Kinetics and Adsorption Capacity

In this study, we describe experimental efforts to decipher the role of ZnCo2O4 nanoflakes (ZCO-NFs) for selective enhancement of voltammetric responses of screen-printed electrode (SPE) toward redox species system. The ZCO-NFs sample was characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and UV–vis spectroscopy. The electrochemical characterization of bare SPE and modified SPE electrodes was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Mott−Schottky analysis. A series of redox systems including paracetamol (PA), dopamine (DA), chloramphenicol (CAP), furazolidone (FZD), p-nitrophenol (p-NP), carbaryl (CBR), ofloxacin (OXF), and erythromycin (ERY) were selected to investigate for (i) reversible redox process, (ii) irreversible electrochemical oxidation process, and (iii) irreversible electrochemical reduction process on both bare-SPE and ZCO-NFs/SPE electrodes. The obtained results showed that ZCO-NFs possess the selective enhancement of electrochemical response for redox systems with an increase of 24%–90% for PAR, DA, FZD, CAP, and CBR and a decrease of 13%–49% for p-NP, ERY, and OFX. The different electrochemical response of redox species at nanostructured semiconductor electrodes is attributed to the contribution of both the adsorption capacity of redox species and the interfacial electron transfer process between electrode and redox species. An insight into the interfacial electron transfer kinetics and its contribution to the enhancement of electrochemical response on p-type semiconductor electrode is helpful in designing high-performance sensing platforms based on spinel oxide nanostructures.

Exploring electron transfer: Bioinspired, biomimetics, and bioelectrochemical systems for sustainable energy and Value-Added compound synthesis

Electron transfer (ET) is a fundamental process that underlies various phenomena in physics, chemistry, and biology. Understanding ET mechanisms is crucial for developing sustainable energy solutions and synthesizing value-added compounds efficiently. In this context, the present review provides the fundamental aspects of ET involving bioinspired, biomimetics, and biological entities and its significance for sustainable energy and green electrosynthesis fields. Among the theoretical and experimental cornerstones, Marcus Theory, electronic conductance, computational modeling, biomolecular thermodynamics, electrochemical and kinetic theories, protein film voltammetry, and the emergence of in situ and operando techniques are explored. Theoretical modeling is vital for understanding and predicting ET processes. Additionally, the significance of experimental techniques for investigating the ET process in biological entities and interfaces is discussed. Protein film voltammetry is a valuable and consolidated technique for studying ET processes at the protein-electrode interface, whereas in situ and operando techniques for interrogating ET processes in real time provide insights into the dynamics and mechanisms of ET. The concept of quantum conductance in biological structures is addressed, evidencing a trend and power of single-entity analysis. Aspects of extracellular and interfacial ET processes are presented and discussed in the electrochemical energy conversion systems. A deep understanding of these processes can improve the design of efficient bioinspired catalysts. Therefore, this multidisciplinary work aims to fill the gaps between different scientific fields related to ET involving bioentities to develop innovative energy and value-added compound synthesis solutions.

Interfacial Bonding Induced Charge Transfer in Two-Dimensional Amorphous MoO3-x/Graphdiyne Oxide Non-Van der Waals Heterostructures for Dominant SERS Enhancement.

Two-dimensional semiconductor-based nanomaterials have shown to be an effective substrate for Surface-enhanced Raman Scattering (SERS) spectroscopy. However, the enhancement factor (EF) tends to be relatively weak compared to that of noble metals and does not allow for trace detection of molecules. In this work, we report the successful preparation of two-dimensional (2D) amorphous non-van der Waals heterostructures MoO3-x/GDYO nanomaterials using supercritical CO2. Due to the synergistic effect of the localized surface plasmon resonance (LSPR) effect and the charge transfer effect, it exhibits excellent SERS performance in the detection of methylene blue (MB) molecules, with a detection limit as low as 10-14 M while the enhancement factor (EF) can reach an impressive 2.55×1011. More importantly, the chemical bond bridging at the MoO3-x/GDYO heterostructures interface can accelerate the electron transfer between the interfaces, and the large number of defective surface structures on the heterostructures surface facilitates the chemisorption of MB molecules. And the charge recombination lifetime can be proved by a ~1.7-fold increase during their interfacial electron-transfer process for MoO3-x/GDYO@MB mixture, achieving highly sensitive SERS detection.

Unveiling photoinduced electron transfer in cobalt(iii)-R-pyridine complexes anchored to anatase nanocrystals: photoluminescence and magnetic studies.

In this study, we synthesized mixed ligand complexes of the cis-[Co(tn)2(Rpy)Br]Br2 type using a novel mechanochemical approach. Characterization involved spectral measurements and single crystal X-ray diffraction analysis, confirming the structure of the cis-[Co(tn)2(4-Mepy)Br]Br2 complex. The single crystal refinement data revealed a monoclinic crystal system with a distorted octahedral geometry. The choice of the sixth ligand influenced the emission and magnetic properties, showing a ferromagnetic character in the Co(iii)-complex environment. We investigated efficient electron transfer to the cobalt(iii) center using TiO2 nanoparticles under UV-light irradiation. The adsorption characteristics of cis-[Co(tn)2(Rpy)Br]Br2 in aqueous 2-propanol varied, leading to surface compound formation. Under UV irradiation, the anatase surface exhibited remarkable adsorption capabilities, facilitating efficient electron transfer to the Co(iii) center and resulting in a high photoefficiency for Co(ii) formation. Our study has put forward a model for interfacial electron transfer (IET), taking into account the overlap between the TiO2 conduction band and the acceptor level of the Co center, as well as the electronic coupling between the donor level of the Ti center and the acceptor level of the Co center. This model sheds light on the accumulation of electrons for reducing the adhered complex ion. The IET process was corroborated by the conversion of 2-propanol into acetone, as verified by 1H NMR technique. Overall, our findings provide novel insights into the role of the Rpy moiety in modifying the structure of the TiO2-cobalt(iii)-Rpy compound and propose a mechanism for IET reactions, thus advancing the field.

Enhancing the Carrier Transport in Monolayer MoS2 through Interlayer Coupling with 2D Covalent Organic Frameworks.

The coupling of different 2D materials (2DMs) to form van der Waals heterostructures (vdWHs) is a powerful strategy for adjusting the electronic properties of 2D semiconductors, for applications in opto-electronics and quantum computing. 2D molybdenum disulfide (MoS2 ) represents an archetypical semiconducting, monolayer thick versatile platform for the generation of hybrid vdWH with tunable charge transport characteristics through its interfacing with molecules and assemblies thereof. However, the physisorption of (macro)molecules on 2D MoS2 yields hybrids possessing a limited thermal stability, thereby jeopardizing their technological applications. Herein, the rational design and optimized synthesis of 2D covalent organic frameworks (2D-COFs) for the generation of MoS2 /2D-COF vdWHs exhibiting strong interlayer coupling effects are reported. The high crystallinity of the 2D-COF films makes it possible to engineer an ultrastable periodic doping effect on MoS2 , boosting devices' field-effect mobility at room temperature. Such a performance increase can be attributed to the synergistic effect of the efficient interfacial electron transfer process and the pronounced suppression of MoS2 's lattice vibration. This proof-of-concept work validates an unprecedented approach for the efficient modulation of the electronic properties of 2D transition metal dichalcogenides toward high-performance (opto)electronics for CMOS digital circuits.

Electron Transfer Mechanism at the Interface of Multi-Heme Cytochromes and Metal Oxide.

Electroactive microbial cells have evolved unique extracellular electron transfer to conduct the reactions via redox outer-membrane (OM) proteins. However, the electron transfer mechanism at the interface of OM proteins and nanomaterial remains unclear. In this study, the mechanism for the electron transfer at biological/inorganic interface is investigated by integrating molecular modeling with electrochemical and spectroscopic measurements. For this purpose, a model system composed of OmcA, a typical OM protein, and the hexagonal tungsten trioxide (h-WO3 ) with good biocompatibility is selected. The interfacial electron transfer is dependent mainly on the special molecular configuration of OmcA and the microenvironment of the solvent exposed active center. Also, the apparent electron transfer rate can be tuned by site-directed mutagenesis at the axial ligand of the active center. Furthermore, the equilibrium state of the OmcA/h-WO3 systems suggests that their attachment is attributed to the limited number of residues. The electrochemical analysis of OmcA and its variants reveals that the wild type exhibits the fastest electron transfer rate, and the transient absorption spectroscopy further shows that the axial histidine plays an important role in the interfacial electron transfer process. This study provides a useful approach to promote the site-directed mutagenesis and nanomaterial design for bioelectrocatalytic applications.

Boron doped diamond electrode for efficient persulfate generation: The modulation of boron doping level on interfacial electron transfer

The inefficient Faradaic efficiency of electro-synthesis of sodium persulfate (Na2S2O8) hinders its industrial application. In this work, modulated high-performance boron-doped-diamond (BDD) electrodes were used to Na2S2O8 electro-synthesis. The effect of boron doping level of BDD electrode on Na2S2O8 generation was studied for the first time. Based on electro-synthesis results, BDD (0.05% B) electrode produced more Na2S2O8 (41.85 mM at 120 min) with the Faradaic efficiency of 90% that is the highest value reported in the literatures. Na2S2O8 was generated by ·OH mediated indirect oxidation, and the BDD (0.05% B) electrode produced more ·OH. Furthermore, the less C-O functional groups on the BDD (0.05% B) electrode surface inhibited the interfacial electron transfer of H2O to O2, and therefore promoted ·OH formation. These findings highlight the relationship between boron doping level, surface functional groups, interfacial electron transfer process and Na2S2O8 generation, providing a theoretical guidance for efficient Na2S2O8 electro-synthesis.

Ligand enhanced bio-oxidation of structural Fe(II) in illite coupled with nitrate reduction

Coupled reaction of Fe(II) oxidation and nitrate reduction plays an important role in biogeochemical cycling of Fe and N, but biologically redox-inert clay minerals are seldom considered in this process. Herein, we report significant effects of ethylenediaminetetraacetic acid (EDTA) and oxalate on microbial oxidation of structural Fe(II) in illite and montmorillonite when coupled with reduction of nitrate in the presence of Pseudogulbenkiania sp. strain 2002. Without ligand, the extent of structural Fe(II) oxidation in illite was low and delayed. Because intracellular organic matter served as a more bioavailable electron donor, the molar ratio of Fe(II) oxidation relative to nitrate reduction (<0.04) was much lower than the expected stoichiometric ratio (=5). However, ligand amendment markedly shortened the lag time, enhanced Fe(II) oxidation, and resulted in a higher ratio of Fe(II) oxidation relative to nitrate reduction (=0.15). EDTA showed a greater enhancement effect than oxalate, due to its higher complexation ability. The likely reason was the formation of Fe(II)-ligand complex through ligand-induced partial dissolution of illite, which was oxidized more easily than structural Fe(II) in illite. The resulting Fe(III)-ligand complex was re-reduced by structural Fe(II) in illite via an interfacial electron transfer process. Therefore, Fe(III)-ligand/Fe(II)-ligand complexes effectively served as electron shuttle between illite and cells to enhance Fe(II) oxidation in illite. The ligand-promoting effect was less significant for montmorillonite, likely because its structural Fe(II) was already more bioavailable than that in illite. Our results reveal the significant role of natural ligands in expanding the electron pool available to support microbial oxidation of solid-state Fe(II) in soils and sediments and have important implications for coupled Fe and N cycles and other biogeochemical processes in the environment.

Tunable Photoinduced Charge Transfer at the Interface between Benzoselenadiazole-Based MOF Linkers and Thermally Activated Delayed Fluorescence Chromophore.

Structural modifications to molecular systems that lead to the control of photon emission processes at the interfaces between photoactive materials play a key role in the development of fluorescence sensors, X-ray imaging scintillators, and organic light-emitting diodes (OLEDs). In this work, two donor-acceptor systems were used to explore and reveal the effects of slight changes in chemical structure on interfacial excited-state transfer processes. A thermally activated delayed fluorescence (TADF) molecule was chosen as the molecular acceptor. Meanwhile, two benzoselenadiazole-core MOF linker precursors, Ac-SDZ and SDZ, with the presence and absence of a C≡C bridge, respectively, were carefully chosen as energy and/or electron-donor moieties. We found that the SDZ -TADF donor-acceptor system exhibited efficient energy transfer, as evidenced by steady-state and time-resolved laser spectroscopy. Furthermore, our results demonstrated that the Ac-SDZ-TADF system exhibited both interfacial energy and electron transfer processes. Femtosecond-mid-IR (fs-mid-IR) transient absorption measurements revealed that the electron transfer process takes place on the picosecond timescale. Time-dependent density functional theory (TD-DFT) calculations confirmed that photoinduced electron transfer occurred in this system and demonstrated that it takes place from C≡C in Ac-SDZ to the central unit of the TADF molecule. This work provides a straightforward way to modulate and tune excited-state energy/charge transfer processes at donor-acceptor interfaces.

Amine Hole Scavengers Facilitate Both Electron and Hole Transfer in a Nanocrystal/Molecular Hybrid Photocatalyst

A well-known catalyst, fac-Re(4,4'-R2-bpy)(CO)3Cl (bpy = bipyridine; R = COOH) (ReC0A), has been widely studied for CO2 reduction; however, its photocatalytic performance is limited due to its narrow absorption range. Quantum dots (QDs) are efficient light harvesters that offer several advantages, including size tunability and broad absorption in the solar spectrum. Therefore, photoinduced CO2 reduction over a broad range of the solar spectrum could be enabled by ReC0A catalysts heterogenized on QDs. Here, we investigate interfacial electron transfer from Cd3P2 QDs to ReC0A complexes covalently bound on the QD surface, induced by photoexcitation of the QD. We explore the effect of triethylamine, a sacrificial hole scavenger incorporated to replenish the QD with electrons. Through combined transient absorption spectroscopic and computational studies, we demonstrate that electron transfer from Cd3P2 to ReC0A can be enhanced by a factor of ∼4 upon addition of triethylamine. We hypothesize that the rate enhancement is a result of triethylamine possibly altering the energetics of the Cd3P2-ReC0A system by interacting with the quantum dot surface, deprotonation of the quantum dot, and preferential solvation, resulting in a shift of the conduction band edge to more negative potentials. We also observe the rate enhancement in other QD-electron acceptor systems. Our findings provide mechanistic insights into hole scavenger-quantum dot interactions and how they may influence photoinduced interfacial electron transfer processes.

Engineering active heterojunction architecture with oxygenated-Co, Mo bimetallic sulfide heteronanosheet and graphene oxide for peroxymonosulfate activation

Bimetallic sulfides have distinctive catalytic property in activating peroxymonosulfate (PMS) for water remediation. Polyoxometalates as potential precursors have rarely been reported for the catalytic degradation of refractory organic pollutants. Herein, a composite catalyst of Co-Mo bimetallic sulfides supported onto graphene oxide (O-CoMoS/GO) with a heterojunction architecture was synthesized through a hydrothermal strategy with polyoxometalates ((NH4)4[CoIIMo6O24H6]·6H2O) as the precursor and applied in the PMS activation. This material showed a superior performance for the catalytic degradation of the model organic pollutant, 4-chlorophenol (rapidly removed within 10 min with an apparent reaction rate constant of 0.5458 min−1). O-CoMoS/GO outperformed most of the reported catalysts in terms of activity and had a strong tolerance towards common organic and inorganic compounds in water, and could perform well in different real water systems. Experimental and theoretical results indicated that the introduction of GO could achieve the enrichment of electrons on the metals and reduce the d band center (εd) of Co close to the Fermi level (εF), thereby facilitating the interfacial electron transfer process. The activation mechanism was due to the as-prepared bimetallic sulfides and the formation of heterojunction structure with GO, where Co(II) as the active center could be regenerated by the adjacent Mo element (as co-catalyst) and by gathering electrons from GO through the Co/Mo-O-C coupling. This work provides insights into the design of bimetallic sulfide catalysts in activating PMS for water remediation.

The catalytic reduction mechanisms of metal-doped TiO2 for nitrate produced from non-thermal discharge plasma: The interfacial photogenerated electron transfer and reduction process

Nitrogen from the air under discharge plasma may yield abundant nitrate causing secondary pollution. In this study, metal-doped TiO2 not only prolonged the lifetime of the generated electrons but also provided efficient active sites for both nitrate reduction and organic matters degradation. Fe/TiO2 was more efficient for phenol removal but did not support NO3− reduction, because the Fe3+/Fe2+ impurity band was beneficial for more rapid •OH generation. Ag/TiO2 was most active for NO3− reduction but least active for phenol removal, because photo-electrons were utilized to generate abundant H2 rather than •OH. The bimetal comprising Ag and Cu facilitated the decomposition of phenol into HCOOH, which could be oxidized to CO2−• on the holes of Ag-Cu/TiO2, while NO3− could be reduced by CO2−•. The combination of plasma with Ag-Cu/TiO2 efficiently oxidized phenol and accelerated NO3− reduction, which can be demonstrated scientific significance for non-thermal discharge plasma technology in wastewater remediation.

Bicomponent Cocatalyst Decoration on Flux-assisted CaTaO2 N Single Crystals for Photocatalytic CO2 Reduction under Visible Light.

Cubic-like CaTaO2 N photocatalysts with high crystallinity and uniform particle size were successfully prepared by the flux-assisted nitridation method. The growth of CaTaO2 N single crystals under different synthesis conditions was systematically investigated to understand the effects of the crystallinity and optical property on photocatalytic performance of CO2 reduction. Moreover, the modification of CaTaO2 N single crystals with core-shell Ni-Ag bicomponent cocatalyst by two-step decoration process gave a 2.4 times higher amount of CO evolution than the deposition of sole Ag cocatalyst, because of the synergistic effects of bicomponent cocatalyst on the interfacial electron transfer and surface catalytic process. This study provides a valuable way to construct high-crystalline photocatalysts with effective bicomponent cocatalyst for visible-light-driven CO2 reduction with H2 O.

Hierarchical Porous Carbon Fibers for Enhanced Interfacial Electron Transfer of Electroactive Biofilm Electrode

The nanoporous carbon fiber materials derived from electrospun polyacrylonitrile (PAN) fibers doped with zeolitic imidazolate framework are developed here and applied in the microbe fuel cell anode for enhanced interfacial electron transfer. Zeolitic imidazolate fram-8 (ZIF-8) could introduce a large number of mesopores into fibers, which significantly promote indirect electron transfer mediated by flavins (IET). Moreover, it is noted that thinner fibers are more suitable for cytochromes-based direct electron transfer (DET). Furthermore, the enlarged fiber interspace strengthens the amount of biofilm loading but a larger interspace between thick fibers would hinder the formation of continuous biofilm. Consequently, the nanoporous carbon fiber derived from PAN/ZIF-8 composite with a 1:1 wt ratio shows the best performance according to its suitable mesoporous structure and optimal fiber diameter, which delivers a 10-fold higher maximum power density in microbial fuel cells compared to carbon fabric. In this work, we reveal that the proportion of IET and DET in the interfacial electron transfer process varies with different porous structures and fiber diameters, which may provide some insights for designing porous fiber electrodes for microbial fuel cells and also other devices of bioelectrochemical systems.

Enhanced radical generation and utilization efficiency by interfacial enrichment and electronic regulation of CuMnO2/CeO2: Processes and mechanism

As a radical predominant reaction, how to enhance the generation and utilization efficiency of radical through interface regulation then to improve its catalytic activity has been the long-term goal to promote its practical application. Realized the redox carrier may play multifunctional roles in catalytic reaction, CeO2 supported CuMnO2 (CuMnO2/CeO2) was successful constructed and the catalytic performance, reaction process and the relevant mechanism were compared with its simple physical mixed form (CuMnO2 + CeO2). It was found that the introduction of CeO2 provided a large specific surface area to strengthen the enrichment of pollutants at the interface (10 % vs 5 % for ofloxacin and 32 % vs 27 % for tetracycline hydrochloride). In addition, the activated CeO2 support enhanced the interfacial electron transfer process and promoted the generation of more highly active Ce3+ in CuMnO2/CeO2. Their synergistic effects shortened the migration distance from the formed radicals to target pollutants, thus improving the generation and utilization efficiency of radicals. So, the ofloxacin degradation rate in CuMnO2/CeO2 catalytic system was 3.25 times higher than that in CuMnO2 system (0.091 min−1vs 0.028 min−1). Moreover, the ion dissolution experiment further confirmed that the CuMnO2/CeO2 catalytic system can effectively reduce the ion dissolution, which was one of the most important parameters for practical application. Thus, this work proposes a strategy for developing high activity and environmentally friendly heterogeneous Fenton catalysts based on the principles of interface enrichment and electronic regulation.

Intermediate Complex-Mediated Interfacial Electron Transfer in a Radical Dianion/TiO2 Dye-Sensitized Photocatalytic System.

We present a mechanistic study of a PTCDA2-/TiO2 dye-sensitized photocatalytic system, in which the stable radical dianion PTCDA2- is formed via a two-step consecutive photoinduced electron transfer from its neutral precursor PTCDA (i.e., perylenetetracarboxylic dianhydride). Photoexcitation of PTCDA2- brings forth an interesting behavior known as vibrationally excited-state-selective, visible-light photocatalytic hydrogen evolution reaction (HER). In conjunction with the information gleaned from optical spectroscopy and ultrafast dynamics, we reveal that an intermediate complex (IC) state with a lifetime of ∼12 ps exists in the vicinity of a certain vibrationally excited state of PTCDA2-. Such a unique IC state mediates the interfacial electron transfer (IET) channel from the specific excited state of PTCDA2- to the conduction band continuum of TiO2. As an outcome, the effective IC-mediated IET process in this photocatalytic system leads to a remarkable HER rate that reaches ∼4660 μmol g-1 h-1.

In situ and operando electrochemistry of redox enzymes

Understanding the biocatalytic or the interfacial electron transfer processes of redox enzymes is decisive to develop high-performance biofuel cells, mimetic catalysts, bioelectrosynthesis reactors, biosensors, and bioelectronic devices. The state-of-art of redox enzyme electrochemistry lies in using in situ and operando instrumentation, in which protein electrochemistry is resourcefully coupled to or hyphenated with numerous analytical techniques. Nevertheless, there is still a lot to research about the manipulation of redox proteins in the unusual sample holding environments, and bioelectrodes engineering emerges as a key. Here, we discuss these challenges in detail, focusing on contemporary instrumentation setups.

Electrochemical aptasensor based on electrodeposited poly(3,4-ethylenedioxythiophene)-graphene oxide coupled with Au@Pt nanocrystals for the detection of 17β-estradiol.

An electrochemical aptasensor is reportedfor the sensitive and specific monitoring of 17β-estradiol (E2) based on the modification of electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT)-graphene oxide (GO) coupled with Au@Pt nanocrystals (Au@Pt). With excellent conductivity, chemical stability and active sites, the PEDOT-GO nanocomposite film was firstly in situ polymerized on the glassy carbon electrode by cyclic voltammetry. Subsequently, one-step synthesized Au@Pt were decorated on the conductive polymer, providing a platform for immobilizing the aptamer and enhancing the detecting sensitivity. With the addition of E2, since the interfacial electron transfer process was retarded by the E2-aptamer complex, the differential pulse voltammetry signal decreased gradually. Under optimum conditions, the calibration curve of E2 exhibited a linear range between 0.1pM and 1nM, with a low detection limit (S/N = 3) of 0.08pM. Thedevelopedaptasensor showed admiring selectivity, stability, and reproducibility. It was tested in human serum, lake water and tap water samples after low-cost and simple pretreatment. Consequently, the developed platform could provide a new design thought for ultrasensitive detection of E2 in clinical and environmental samples.

Electrochemistry of copper efflux oxidase-like multicopper oxidases involved in copper homeostasis

Multicopper oxidases are widely studied enzymes catalyzing the oxygen reduction reaction. Among this family, one class belongs to the copper efflux oxidases. They are far less studied in bioelectrochemistry mainly because of the low potential at which they reduce O 2 . However, the presence of a specific domain rich in methionine residues covering the first copper electron acceptor induces fundamental issues regarding the electron transfer pathway. In addition, as they are involved in copper homeostasis, the understanding of their catalytic mechanism may have important consequences in therapeutic applications. We present here the last findings reported on copper efflux oxidases based on electrochemical tools. We focus on the proposed roles of the methionine-rich domain in the electron transfer process. Especially, copper binding to this domain and consequences on the interfacial electron transfer process appear to be two fundamental aspects to discuss. • Copper efflux oxidases are multicopper oxidases involved in copper homeostasis. • Their activity is influenced by Cu 2+ addition both in solution and at electrodes. • Copper efflux oxidases present a methionine-rich domain not found in other multicopper oxidases. • The role of this methionine-rich domain on the activity of the enzyme is a key issue.

Amending charge separation and migration in TiO2 nanosheet via Au nanoparticles ensemble and its synergy in photoelectrocatalytic methanol oxidation

In this report, the preparation of an ensemble of hydrothermally synthesized TiO 2 nanosheets with Au nanoparticles (TiO 2 NSs-Au NPs) and their photoelectrocatalytic methanol oxidation behavior are accounted. The absorption spectral studies confirmed the successful emergence of Au NPs on TiO 2 NSs ensemble and the existence of Au NPs broadened the light absorption to the visible light spectrum. The crystalline and structural complexity analysis confirms the anatase TiO 2 as a major product in this synthesis. Morphology studies revealed the formation of 2 dimensional TiO 2 NSs with chemically deposited Au NPs at the TiO 2 surface and it was further confirmed by STEM-HAADF-EDS mapping studies. The ITO/TiO 2 NSs-Au modified photoelectrode showed a synergistic catalytic response towards photoelectrocatalytic methanol oxidation than the ITO/TiO 2 NSs electrode. Among them, TiO 2 NSs with 1 mM Au NPs deposited composite (TiO 2 NSs-Au (1)) showed 2-fold higher photocurrent for methanol oxidation than their pristine TiO 2 NSs. The deposited of Au NPs in TiO 2 NSs-Au nanocomposites facilitates the photoinduced charge separation and charge migration processes. Coherently the charge recombination process diminished in the TiO 2 NSs-Au nanocomposite materials. The best synergistic photoelectrocatalytic methanol oxidation reaction at the ITO/TiO 2 NSs-Au (1) modified electrode was achieved via extended visible light absorption with Schottky barrier induced enhancement of interfacial electron transfer process. • Two-dimensional TiO 2 nanosheets modified with Au NPs (TiO 2 NSs-Au). • The ITO/TiO 2 NSs-Au modified electrodes show a synergistic catalytic response. • ITO/TiO 2 NSs-Au shows enhanced photoelectrocatalytic methanol oxidation. • The Schottky barrier enhances the interfacial electron transfer process.