Fluorine-doped Tin Oxide Surface Research Articles

Cerium Ion Adsorption to Fluorine-Doped Tin Oxide Electrodes

The f-elements are critical in many technologies including electronics, catalysis, magnetics, and clean energy. Additionally, these elements occur in very low abundance worldwide. Research has therefore been motivated in the detection, quantification, and reclamation of these elements from waste streams. In this presentation we explore the use of fluorine-doped tin oxide (FTO) electrodes as sensitive and cost-effective electrochemical sensors for cerium ions. We demonstrate that cerium adsorbs reversibly to bare FTO surfaces with a dependence on pH. Through voltammetry and XPS characterization, we demonstrate that the adsorbed cerium, which can undergo the quasi-reversible CeIV/CeIII redox transition, exists in more than one chemical environment. Based on these data, we posit that these different environments are due to the buildup of multiple layers of cerium ions on the FTO surfaces. At lower concentrations (< ca. 100 uM), we can use voltammetry to quantify the cerium adsorbed to the FTO and relate it to the concentration of cerium in solution, with a lower detection limit of about 10-6 M. The data fits to a pseudo second order rate law with a rate constant on the order of 107 (cm2 mol-1)2 s-1. The adsorption fits well to the Freundlich model, but we are working towards finding a non-empirical adsorption model than provide the equilibrium constant for the adsorption reaction.

A Photoelectrochemical and Spectroscopic Studies of Photoelectrodes with Hematite∣Catalyst∣Electrolyte Interface Toward Oxygen Evolution Reaction

One of the recent issues in the world is climate change caused by global warming. Many countries have set an ultimate goal for carbon neutrality to prevent from further increase of the global temperatures. In this regard, research on development of renewable energy sources without any carbon emissions has been intensively conducted. Among many promising chemical fuels with sustainability, Hydrogen (H2) can be produced by water (H2O) splitting.Especially, water splitting driven by photoelectrochemical reactions has great advantages in H2 generation: photovoltage generated by light absorption in semiconductors may significantly reduce the applied overpotential which should be provided by external circuits. This photoelectrochemical system, called photoelectrochemical cell (PEC) for water splitting is basically composed of photoelectrodes, catalysts, and membranes for generation of photogenerated charge carriers, reducing overpotential by improving charge transfer kinetics, and prevention of H2 and Oxygen (O2) crossover, respectively. When photons from solar light with energies greater than band gap are incident on the photoelectrodes, an electron-hole pair (EHP) is formed in the semiconductor. These EHPs are separated and transported to the surface, driven by band bending formed at the semiconductors. In photoanodes, the most of the charge carriers arrived at the electrode surface are holes (h+s), which oxidizes H2O at the photoelectrode-electrolyte interface. The transfer of holes accompanies the proton transfers, thereby producing O2. The separated electrons (e−s) should travel to the (photo)cathode along the external circuit and generate H2. However, the overall efficiency of water splitting using PEC still confronts many challenges for wide commercialization, including the low solar-to-hydrogen (STH) efficiencies. In order to improve the performance, the semiconductor efficiently utilizes the photons in the visible light region, which takes 45% of solar irradiation. In this perspective, hematite (α-Fe2O3) is one of the most promising candidates for the semiconductor as photoanodes owing to is narrow band gap of 1.9 ~ 2.2 eV, which is in the range between 550 ~ 650 nm. Meticulous cares should be also taken in catalysts localization to prevent from the parasitic photon loss, as well as the selection of catalytic materials. Because catalysts attribute to the improved charge transfer kinetics but also simultaneously become the sites that obstruct the light penetration to the semiconductor, resulting in the lower light absorption. Furthermore, physical and chemical composition of catalysts on the semiconductor surface significantly influence the charge transfer rates for the photoelectrochemical reactions by varying the electrical field gradient formed at the semiconductor∣catalyst∣electrolyte interface. As several procedures are additionally involved in the PEC, the electrochemical reaction pathways become more complicated rather than the one in electrolyzers utilizing conductive electrodes. Therefore, underlying understanding in semiconductor∣catalyst∣electrolyte interface is crucial to achieve the high performance in PECs.Herein, we demonstrate the hematite∣catalyst∣electrolyte interface as the photoanodes to investigate the photoelectrochemical reaction pathways in water oxidation. Hematite is the perfect material as the semiconductor model, not only due to the narrow band gap in the region of visible light but also the excellent stability even when exposed to the electrolytes and electrochemical environments. The hematite is fabricated by simple hydrothermal reactions, followed by step-wise heat treatment. The structure of hematite is optimized by varying hydrothermal temperatures, affecting the crystallinity and exposed area of the conductive substrate, fluorine-doped tin oxide (FTO). The recombination by back reduction is occurred at the exposed FTO surface by pinholes in hematite, which directly contact the electrolyte. Moreover, the localization of Co-based catalysts is also easily controlled by light-guided electrodeposition. In this hematite∣catalyst∣electrolyte interface, the overall water oxidation pathways are investigated by photoelectrochemical and Raman spectroscopic studies. It is expected that our study in here contributes to the in-depth understanding on the complicated photoelectrochemical reaction mechanism, might leading to the improved performance for wide commercialization of PEC.

Fabrication and characterization of NFMA/FTO electrochemical thin film by electrodeposition and immersion techniques: An effective detector for H2O2 and sunlight-driven MB degradation

Surface-confined electroactive nanoscale materials (organometallic semiconductors) are being explored as promising alternatives to traditional inorganic semiconductors for redox processes. In response to widespread non-biodegradable dye pollution causing severe environmental threats, urgent and effective methods for dye elimination or conversion are crucially needed. In this study, we successfully fabricated an electrochemical thin film of N-(ferrocenylmethyl) aniline (NFMA) on a fluorine-doped tin oxide (FTO) electrode using immersion and electrochemical deposition techniques. To characterize the NFMA/FTO electrode, we employed XRD, SEM, and UV–Vis spectroscopy. Our results revealed that the deposited NFMA/FTO films exhibited an amorphous structure, as confirmed by XRD analysis. SEM images demonstrated a uniform distribution of small particles on the FTO surface. UV–Vis spectroscopy showed favorable optical properties, indicating a direct band gap of 2.4 eV for electrodeposition film. The NFMA/FTO thin film outperformed FTO electrodes, exhibiting hydrophobic surfaces with contact angles of 73.89° and 78° for immersion and electrodeposition, respectively. The NFMA/FTO electrode exhibited effective electrochemical catalysis for hydrogen peroxide (H2O2) utilizing ferrocene/ferricenium (Fc/Fc+) as an electron-transfer mediator. Under sunlight irradiation, the NFMA/FTO thin film exhibited remarkable degradation efficiency of Methylene Blue (MB), achieving 78% degradation within a reaction duration of 180 min at a concentration of 1 ppm in a 500 mL. The degradation kinetics were found to follow the pseudo-first-order reaction model, yielding rate constant (k) values of 0.0078 min−1. Our findings highlight the potential of surface-confined electroactive nanoscale materials, particularly the NFMA/FTO system, as a promising avenue for various electrochemical and photocatalytic applications.

Electrochemical synthesis of Co-, Ni- and NiCo-based hexacyanocobaltates as efficient electrocatalysts for water oxidation studies

The performance of electrocatalysts for the oxidation of water is a crucial factor in the advancement of future technologies for energy conversion such as nonsegregated solar water-splitting systems and water electrolyzers. Previous research demonstrates indisputably that PBAs' catalytic activity can vary significantly depending on their altered structural makeup and fabrication techniques. In the current study electrodeposition, a binder-free perspective has been applied to synthesize Co-, Ni-, and a rare example of trimetallic NiCo-hexacyanocobaltates as electrocatalysts on the surface of fluorine-doped tin oxide (FTO) substrates. The synthesized materials have been characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS). The water oxidation activity of synthesized materials has been examined in 1 M KOH by measuring their overpotential, Tafel slope, electrochemical active surface area (ECSA), and charge transfer resistance (Rct) values. Results have shown that trimetallic NiCo-hexacyanocobaltate exhibited good electrocatalytic activity for water oxidation reaction with an overpotential of 331 mV versus RHE at 10 mA cm-2 current density, 48 mV/dec Tafel slope, and 75 cm2 ECSA.

Antireflection effect of high haze FTO for improving short circuit current density of perovskite solar cells

The optical properties of fluorine-doped tin oxide (FTO) coated glass substrates will limit the short circuit current density (Jsc), thus the power conversion efficiency (PCE) of perovskite solar cells (PSCs). This work compares the transmittance, reflectance, haze, and surface roughness of different FTO glass substrates. Then the performance of the PSCs, which were fabricated on these substrates, is discussed. The analysis indicates that higher haze FTO glass substrates with higher surface roughness are effective for the reduction of light reflection from NiOx-deposited FTO substrates/perovskite interfaces, leading to higher Jsc and thus the higher PCE of the PSCs. The antireflection effect is attributed to light absorption by the perovskite layer via multiple reflections due to the very rough FTO surface texture.

PEC thrombin aptasensor based on Ag–Ag2S decorated hematite photoanode with signal-down effect of precipitation catalyzed by G-quadruplexes/hemin

A photoelectrochemical (PEC) aptasensor for thrombin detection was rationally designed based on the photoanode of one-dimensional hematite nanorods (α-Fe2O3 NRs) with several steps of modifications. Uniform α-Fe2O3 NRs were grown vertically on the surface of fluorine-doped tin oxide (FTO) conductive glass through a one-step hydrothermal method; then Ag was grown on the surface of α-Fe2O3 NRs through a photoreduction method followed by a partial in-situ transformation into Ag2S, conferring an improvement on the initial photocurrent. Two main critical factors, namely, the steric hindrance of thrombin, benzoquinone (BQ) precipitation oxidized by H2O2 under the catalysis of G-quadruplexes/hemin, contributed to the sensitive signal-down response toward the target. Photocurrent signals related with thrombin concentration was established for thrombin analysis due to the non-conductive complex as well as their competitive consumption of electron donors and irradiation light. The excellent initial photocurrent was combined with the signal-down amplification in the design of the biosensor, conferring a limit of detection (LOD) as low as 40.2 fM and a wide linear range from 0.0001 nM to 50 nM for the detection of thrombin. The proposed biosensor was also assessed in terms of selectivity, stability, and applicability in human serum analyses, which provided an appealing maneuver for the specific analysis of thrombin in trace amount.

Electrochemical and Optical Properties of Fluorine Doped Tin Oxide Modified by ZnO Nanorods and Polydopamine

Various forms of zinc oxide (ZnO) are frequently used in the design of optical and electrochemical sensors. However, the optical and electrochemical properties of ZnO should be properly adjusted depending on the application area. Therefore, in this work, we have investigated changing/tuning the properties of ZnO by depositing a layer of polydopamine (PDA) on its surface. In order to perform this investigation, the surface of fluorine-doped tin oxide (FTO) was modified with the layer of ZnO nanorods and PDA. ZnO nanorods were synthesized by hydrothermal synthesis technique, and after the synthesis, they were coated with polydopamine exploiting the self-polymerization of dopamine. The nanostructures were investigated by using electrochemical and optical methods. Electrochemical impedance spectroscopy measurements showed that electrochemical properties of FTO-ZnO and FTO-ZnO-PDA nanostructures could be changed by the variation of both—applied electrical potential and/or exposition towards lighting. Interaction between ZnO-PDA and bovine serum albumin (BSA) molecules has been investigated by (photo)electrochemical and photoluminescence methods. A mechanism of possible interaction between BSA and the ZnO-PDA surface has been proposed.

Electrochemical stability and corrosion mechanism of fluorine-doped tin oxide film under cathodic polarization in near neutral electrolyte

Commercial fluorine-doped tin oxide (FTO) coated glass slides were subjected to different cathodic potentials for 15 min in 0.2 M Na2SO4 of pH 6.42 to study their electrochemical stability. Results showed that FTO could maintain its electrochemical stability until -1200 mV. However, when it was cathodically polarized from -1600 mV to more negative potentials, band structure positions started to shift upwards, the electrolyte became more acidic and a porous structure appeared on the FTO surface. At -2000 mV, a layer of metallic Sn was seen deposited on the FTO surface, verified by X-ray diffraction and scanning electron microscopy – energy dispersive X-ray spectroscopy. During the cathodic corrosion in near neutral electrolyte, the reduction of SnO2 to Sn involves water oxidation as well as hydrogen evolution reaction.

Electrochemical investigation of freshwater biofilm on FTO surface: Oxide film perspective

AbstractThe contemporary field of bacterial biofilm electrophysiology is a greater importance to understanding the interfaces of active biofilm/material. The electrophysiology of freshwater active biofilm was studied using Fluorine‐doped tin oxide (FTO) electrodes. The open circuit potential and microscopic studies were revealed the attachment of biofilm on the FTO surface. The shift of potential to noble direction up to +402 mV vs SCE was observed on the FTO after 240 h exposure of freshwater. The open‐circuit potential (OCP) was revealed the attachment of biofilm on the FTO surface. Cyclic Voltammetry studies were employed to analyze the redox behavior of biofilm on FTO with different time intervals. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were also used to analyze the electrochemical communications between FTO and biofilm interfaces. The present work was investigated to explain electrochemical interfaces between n‐type oxide film and electro active bacterial biofilm.

Smartphone-based dynamic measurements of electro-optically modulated lossy-mode resonance and its biosensing applications

In this work, we discuss an application of a smartphone-based spectrometer for dynamic analysis of optical response of an electro-optically modulated lossy-mode resonance (LMR) optical fiber sensor. The LMR was achieved when a section of a multimode optical fiber core was coated with a fluorine-doped tin oxide (FTO) thin film. The FTO, thanks to its electrical properties, has been simultaneously applied as an electrochemical electrode. It has been shown that when an electrical potential is applied to the obtained dual-domain sensor, the distribution of charge carriers in the FTO changes and it can be dynamically measured optically using the smartphone-based spectrometer with a time resolution below 0.5 s. Moreover, when charge carriers' accumulation is induced at the FTO surface, the changes on the sensor surface, such as biomaterial binding, can be identified with the device. The optical label-free biosensing performance of the system has been verified using streptavidin and green fluorescent protein (GFP) as receptor and target, respectively. The outcome of optical and electrical measurements, acquired simultaneously, were compared. It has been found that the system can detect concentration of GFP as low as 1 ng/mL. It must be noted that the smartphone-based dynamic optical measurements were possible with only the device, a low-cost detachable adapter, and a custom-made software application. Electrical measurements using a smartphone with such low-cost modifications are hardly possible. The setup can be further simplified using just a battery for setting the potential difference, thus establishing electro-optical modulation of the sensor. Such a system may be considered as suitable for a broad spectrum of sensors and their label-free biosensing applications.

Formation of mixed hybrid bilayer lipid membrane on transparent thin film oxide electrodes

In this work, we attempted to design phospholipid bilayers tethered to semiconducting metal oxide films. The phospholipid layers assembled on compact monocomponent self-assembled monolayers (SAM) on oxide films were accomplished earlier; however, previous studies indicated a poor ability of these layers to functionally reconstitute transmembrane proteins. Commercially available fluorine doped tin oxide (FTO) sheet glass was chosen as a model solid support. FTO surface was functionalised utilising by the mixture of the long and short chain hydrophobic silanes. Specifically, octadecyltrichlorosilane (OTS) and vinyltrimethoxysilane (VTS) were used to assemble mixed silane-based SAMs on FTO. Exposure of mixed SAMs to a solution of multilamellar vesicles of 1,2-dioleoylsn- glycero-3-phosphocholine (DOPC) and 40% cholesterol triggered the changes of electrochemical parameters commensurate with the formation of additional dielectric layers of phospholipids.

Nano Ag-enhanced photoelectric conversion efficiency in all-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells

All-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells have great potential for development, but their device performance needs to be further improved. Recently, metal nanostructures have been successfully applied in the field of solar cells to improve their performance. Nano Ag-enhanced power conversion efficiency (PCE) in one CsPbIBr2 perovskite solar cell utilizing localized surface plasmons of Ag nanoparticles (NPs) on the surface has been researched experimentally and by simulation in this paper. The localized surface plasmon resonance of Ag NPs has a near-field enhancement effect, which is expected to improve the light absorption of CsPbIBr2 perovskite photovoltaic devices. In addition, Ag NPs have a forward-scattering effect on the incident light, which can also improve the performance of CsPbIBr2-based perovskite photovoltaic devices. By directly assembling Ag NPs (with a size of about 150 nm) on the surface of fluorine-doped tin oxide it is found when the particle surface coverage is 10%, the CsPbIBr2 perovskite photovoltaic device achieves a best PCE of 2.7%, which is 9.76% higher than that of the control group. Without changing any existing structure in the ready-made solar cell, this facile and efficient method has huge applications. To the best of our knowledge, this paper is the first report on nano Ag-enhanced photoelectric conversion efficiency in this kind of CsPbIBr2 perovskite solar cell.

Development of a Binder-Free Tetra-Metallic Oxide Electrocatalyst for Efficient Oxygen Evolution Reaction

Water splitting has emerged as a sustainable, renewable and zero-carbon-based energy source. Water undergoes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) during electrolysis. However, among these half-cell reactions, OER is more energy demanding. Hence, the development of efficient catalysts for speeding up OER is a key for boosting up the commercial viability of electrolyzers. Typical binders like Nafion and PVDF are not preferred for designing commercial electrocatalysts as they can compromise conductivity. Thus, we have designed a novel and cost-effective binder-free tetra-metallic (Co-Cu-Zn-Fe) oxide catalyst that efficiently catalyzes OER. This catalyst was grown over the surface of Fluorine doped tin oxide (FTO) transducer by a facile potentiodynamic method. The structure and morphology of the modified electrode were characterized by X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive X-ray spectroscopy. XRD analysis confirmed the deposition of CoFe2O4 and CuCo2O4 along with alloy formation of Co-Fe and Co-Cu. Similarly, EDX and SEM results show the presence of metals at the surface of FTO in accordance with the results of XRD. Linear scan voltammetry was employed for testing the performance of the catalyst towards accelerating OER in strongly alkaline medium of pH-13. The catalyst demonstrated stunning OER catalytic performance, with an overpotential of just 216 mV at 10 mA cm−2 current density. Moreover, the chronopotentiometric response revealed that the designed catalyst was stable at a potential of 1.80 V for 16 h. Thus, the designed catalyst is the first example of a highly stable, efficient, and inexpensive catalyst that catalyzes OER at the lowest overpotential.

Morphological and functional characterizations of SnO2 electron extraction layer on transparent conductive oxides in lead-halide perovskite solar cells

Optimization of carrier extraction and/or transport layers is an important factor for the development of perovskite semiconductor devices. In particular, tin dioxide, SnO2, is being frequently used as an electron transport layer (ETL) in perovskite solar cells. However, a systematic study on preparation and characterization of the SnO2-ETL is still lacking, and thus, morphological and electronic-functional roles are not fully understood. In this paper, we systematically investigate the SnO2-ETL prepared on fluorine-doped tin oxide (FTO) substrates by a spin-coating technique. Using microscopic observations, we morphologically study how the SnO2 film covers the FTO surface with large unevenness. Optical characterizations are employed for investigating an electronic band alignment of the perovskite/SnO2 interface varied with the SnO2 concentration in a solution. Furthermore, we systematically evaluate photovoltaic properties of FTO-based solar cell devices. A major finding from these investigations is the fact that while the SnO2-ETL prepared at the adequate condition exhibits an ideal band alignment, the excessive SnO2 deposition causes a poor electron extraction and device performance degradation. Furthermore, we show that the spin-coated SnO2-ETL can cover the FTO surface as an ultrathin wrapping layer. These results highlight the importance of the SnO2-ETL and pave the way for optoelectronic device applications of perovskite materials.

Exploring dopant effects in stannic oxide nanoparticles for CO2 electro-reduction to formate

The electrosynthesis of formate from CO2 can mitigate environmental issues while providing an economically valuable product. Although stannic oxide is a good catalytic material for formate production, a metallic phase is formed under high reduction overpotentials, reducing its activity. Here, using a fluorine-doped tin oxide catalyst, a high Faradaic efficiency for formate (95% at 100 mA cm−2) and a maximum partial current density of 330 mA cm−2 (at 400 mA cm−2) is achieved for the electroreduction of CO2. Furthermore, the formate selectivity (≈90%) is nearly constant over 7 days of operation at a current density of 100 mA cm−2. In-situ/operando spectroscopies reveal that the fluorine dopant plays a critical role in maintaining the high oxidation state of Sn, leading to enhanced durability at high current densities. First-principle calculation also suggests that the fluorine-doped tin oxide surface could provide a thermodynamically stable environment to form HCOO* intermediate than tin oxide surface. These findings suggest a simple and efficient approach for designing active and durable electrocatalysts for the electrosynthesis of formate from CO2.

Tethered Bilayer Membrane Formation on Silanized Fluorine Doped Tin Oxide Surface

Silane compound was synthesized via click chemistry and a mixture of synthesis products without purification was used to form the self-assembled monolayers on metal oxide conducting films of fluorine doped tin oxide (FTO). Silanized FTO surfaces triggered rupture of multilamellar vesicles and formed electrically insulating tethered bilayer membranes (tBLMs). In contrast to well-known hybrid bilayer membranes on silane monolayers such as ones formed from octadecyltrichlorosilane, tBLMs on FTO contained water-ion reservoir between solid surface and phospholipid bilayer sheet. They demonstrated biological relevance and ability to reconstitute the pore-forming protein channels such as α-hemolysin from Staphylococcus aureus and melittin. The addition of cholesterol to tBLMs decreased the membrane-damaging effect of melittin, while the opposite was observed in the case of α-hemolysin. The tBLMs can be regenerated multiple times without losing their functionality. The described methodology (both synthesis and formation of anchor monolayer) can be extended to any oxide film surface by properly adjusting chemical composition of molecular anchor and silanization conditions. This makes the proposed biomimetic membrane system attractive for various applications including biomedical sensors for the detection of pore-forming toxins.

Development of novel electrochemical sensor based on PtNPs-SeNPs-FTO nanocomposites via electrochemical deposition for detection of hydrogen peroxide

The PtNPs-SeNPs-FTO nanocomposites as electrochemical sensor was developed via electrochemical deposition method for hydrogen peroxide detection. The synthesis and growth of selenium nanoparticles (SeNPs), platinum nanoparticles (PtNPs) and nanocomposites of PtNPs-SeNPs on fluorine doped tin oxide (FTO) substrate by using electrochemical deposition for H2O2 detection was reported. Morphological and structural study of bare FTO, PtNPs-FTO, SeNPs-FTO and PtNPs-SeNPs-FTO sensor was confirmed by FEGSEM, EDS mapping, and XPS. Morphology of synthesized PtNPs and SeNPs decorated on the FTO surface showed nano-flower structure and spherical in shape respectively. The XPS analysis was carried out to identify elemental composition on the surface-modified PtNPs-SeNPs-FTO sensor. The survey spectra of PtNPs-SeNPs-FTO electrode displayed a considerable strong peak of C, F, Sn, O, Pt, and Se, which confirmed the existence of these elements on the FTO surface. The synthesized SeNPs-FTO, PtNPs-FTO, and PtNPs-SeNPs-FTO sensor displayed wide range of linear concentration response from 0.01 to 40 mM and response time 0.5 s. The synthesized SeNPs-FTO, PtNPs-FTO and PtNPs-SeNPs-FTO sensor showed sensitivity of 0.4 µA mM−1 cm−2 (R2 =0.9904), 17.2 µA mM−1 cm−2 (R2 =0.9917) and 7.3 µA mM−1 cm−2 (R2 = 0.9835) respectively. The SeNPs-FTO, PtNPs-FTO and PtNPs-SeNPs-FTO based sensor also demonstrated high selectivity towards detection of H2O2 with interfering agents.

An antifouling impedimetric sensor based on zinc oxide embedded polyvinyl alcohol nanoplatelets for wide range dopamine determination in the presence of high concentration ascorbic acid

Dopamine determination is of great importance for the early diagnosis of neurological diseases. However, dopamine sensors mostly encounter important challenges such as surface fouling and interference of co-existing biochemicals. Here, nanoplatelets of zinc oxide embedded polyvinyl alcohol (NP-ZnO/PVA) were utilized for providing an efficient fouling-free surface for selective dopamine determination in concentrations as high as 3 mM of dopamine in the presence of ascorbic acid interference. The fouling-free properties was provided mainly by pH-inducibility of the NP-ZnO/PVA nanocomposite at the rationally adjusted sensing conditions. ZnO plays a vital role in the electrocatalytic oxidation of dopamine, and PVA provides surface functional groups that minimize the surface interactions with interferences or fouling agents. The NP-ZnO/PVA nanocomposite fabrication process was performed by PVA assisted ZnO electro-synthesis onto the surface of fluorine-doped tin oxide (FTO) conducting glass. The fabricated FTO/NP-ZnO/PVA sensor was characterized utilizing FE-SEM, EDX, XRD, TGA-DTG, BET-BJH and FTIR techniques. Impedimetric determination of dopamine was performed in the wide linear range from 20.0 nM to 3.0 mM with a low detection limit of 5.0 nM. The applicability of FTO/NP-ZnO/PVA for dopamine determination was successfully tested in real samples. The NP-ZnO/PVA provides a great prospective to be an efficacious material for the construction of dopamine electrochemical sensing platforms.

Electrochemically Deposited Amorphous Cobalt-Nickel-Doped Copper Oxide as an Efficient Electrocatalyst toward Water Oxidation Reaction.

Production of hydrogen through water splitting is one of the green and the most practical solutions to cope with the energy crisis and greenhouse effect. However, oxygen evolution reaction (OER) being a sluggish step, the use of precious metal-based catalysts is the main impediment toward the viability of water splitting. In this work, amorphous copper oxide and doped binary- and ternary-metal oxides (containing CoII, NiII, and CuII) have been prepared on the surface of fluorine-doped tin oxide by a facile electrodeposition route followed by thermal treatment. The fabricated electrodes have been employed as efficient binder-free OER electrocatalysts possessing a high electrochemical surface area due to their amorphous nature. The cobalt–nickel-doped copper oxide (ternary-metal oxide)-based electrode showed promising OER activity with a high current density of 100 mA cm–2 at 1.65 V versus RHE that escalates to 313 mA cm–2 at 1.76 V in alkaline media at pH 14. The high activity of the ternary-metal oxide-based electrode was further supported by a smaller semicircle in the Nyquist plot. Furthermore, all metal-oxide-based electrodes offered high stability when tested for continuous production of oxygen for 50 h. This work highlights the synthesis of efficient and cost-effective amorphous metal-based oxide catalysts to execute electrocatalytic OER employing an electrodeposition approach.

Novel method for synthesis of reduced graphene oxide–Cu2S and its application as a counter electrode in quantum-dot-sensitized solar cells

Reduced graphene oxide (rGO)-Cu2S as a counter electrode (CE) is synthesized by a novel electrochemical method for quantum-dot-sensitized solar cell (QDSSC) applications. One-step electrochemical co-reduction using cyclic voltammetry for various cycles (3, 5, and 7), followed by sulfurization, is employed to obtain rGO-Cu2S CEs on the surface of fluorine-doped tin oxide. Compared with Pt and Cu2S CEs, rGO-Cu2S CEs (5) display lower charge transfer resistance (Rct) and higher electrocatalytic activity. This is because the introduction of rGO along with Cu2S in the rGO-Cu2S surface enhances the surface area and charge transfer and improves the electrical contact between the CEs and substrate surface. An optimum power conversion efficiency (η) of 4.26% is recorded for rGO-Cu2S (5) in CdS/CdSe/ZnS QDSSCs using a polysulfide electrolyte. QDSSCs with rGO-Cu2S (5) showed the highest short-circuit current density (Jsc) of 17.2 mA cm−2, open circuit voltage (Voc) of 0.57 V, and fill factor of 44%. The obtained results are superior to those for Cu2S (3.77%) and Pt (2.44%) CEs. Additionally, the preparation method of rGO-Cu2S CEs is more scientific, less time-consuming, economical, and easy.