Derivative Voltammetry Research Articles

The Effect of SnO<sub>2</sub> and Rh on Pt Nanowire Catalysts for Ethanol Oxidation

In this study, we synthesized Pt-Rh nanowires (NWs) through chemical reduction of metallic precursors using formic acid at room temperature, excluding the use of surfactants, templates, or stabilizing agents. These NWs were supported on two substrates: carbon (Vulcan XC-72R) and carbon modified with tin oxide (SnO<sub>2</sub>) via the sol-gel method (10 wt.% SnO<sub>2</sub>). We explored the electroactivity of Pt/SnO<sub>2</sub>/C, Pt-Rh/C, Pt-Rh/SnO<sub>2(commercial)</sub>/C (commercial SnO<sub>2</sub>), and Pt-Rh/SnO<sub>2</sub>/C NWs toward electrochemical oxidation of ethanol in acidic media using various techniques, including CO-stripping, cyclic voltammetry, derivative voltammetry, chronoamperometry, and steady-state polarization curves. Physical characterization involved X-ray diffraction and transmission electron microscopy. The synthesized NWs exhibit higher ethanol oxidation activity than the commercial Pt/C (Johnson Matthey™) catalyst. Rh atoms are hypothesized to enhance complete ethanol oxidation, while the NW morphology improves ethanol adsorption at the catalyst surface for subsequent oxidation. Additionally, the choice of support material plays a significant role in influencing the catalytic activity. The superior catalytic activity of Pt-Rh/SnO<sub>2</sub>/C NWs may be attributed to the facile dissociation of the C-C bond, low CO adsorption (electronic effect due to Rh presence), and the bifunctional mechanism facilitated by the oxophilic nature of the SnO<sub>2</sub> support.

Enabling Direct Photoelectrochemical H₂ Production using Alternative Oxidation Reactions on WO₃.

The efficient and inexpensive conversion of solar energy into chemical bonds, such as in H2 via thephotoelectrochemical splitting of H2O, is a promising route to produce green industrial feedstocks and renewablefuels, which is a key goal of the NCCR Catalysis. However, the oxidation product of the water splitting reaction,O2, has little economic or industrial value. Thus, upgrading key chemical species using alternative oxidationreactions is an emerging trend. WO3 has been identified as a unique photoanode material for this purpose sinceit performs poorly in the oxygen evolution reaction in H2O. Herein we highlight a collaboration in the NCCRCatalysis that has gained insights at the atomic level of the WO3 surface with ab initio computational methodsthat help to explain its unique catalytic activity. These computational efforts give new context to experimentalresults employing WO3 photoanodes for the direct photoelectrochemical oxidation of biomass-derived 5-(hydroxymethyl)furfural. While yield for the desired product, 2,5-furandicarboxylic acid is low, insights into the reactionrate constants using kinetic modelling and an electrochemical technique called derivative voltammetry, giveindications on how to improve the system.

The effect of Pt surface orientation on the oscillatory electro-oxidation of glycerol

• The anion (bi)sulfate of the electrolyte exerts a strong influence on the electro-oxidation of glycerol on basal and stepped Pt single crystal surfaces. • Cyclic voltammetry reveals that when there is an increase in sulfate concentration, the glycerol oxidation current density decreases. • Chronoamperometric studies showed that Pt(110) and stepped surfaces exhibited greater ability to catalyze the glycerol electro-oxidation than Pt(111). • Emergence of potential oscillations obtained during glycerol oxidation over Pt( hkl ) and stepped surfaces highlights different mechanisms of the reaction. In the present paper, we have studied the influence of (bi)sulfate anion (0.1 and 0.5 M) on the electro-oxidation of glycerol on basal Pt( hkl ) and stepped surfaces belonging to the series of Pt(S)[ n (111) x (111)]. Cyclic voltammograms and derivative voltammetry pointed out that the catalytic activity decreases for Pt(111) and Pt(110) and, to a minor extent, for stepped surfaces in 0.5 mol L -1 H 2 SO 4. Chronoamperometric curves demonstrated that above 0.60 V ( vs. RHE), for both concentrations (0.1 and 0.5 mol L -1 H 2 SO 4 ), stepped surfaces and Pt(110) showed greater ability to catalyze the glycerol electro-oxidation in comparison with Pt(111). Potential oscillations were mapped along with slow galvanodynamic sweeps and studied at constant current. For Pt(111), no oscillations were found in the galvanodynamic regime, however, under the galvanostatic regime, period 1 oscillations were observed after a long induction period. The oscillations showed a very similar profile for stepped surfaces, even for the Pt(332) surface, which has a high density of (110) steps. Pattern changes were observed only for Pt(110) compared to other surfaces. Therefore, we conclude that (110) step sites influence the oscillatory behavior, thus the insertion of the steps favors the path of formation of inactive species, which compete for the same catalytic sites in a given potential region. The extinction of the mechanism oscillatory occurs differently due to the intrinsic characteristics of each surface electrode for the formation of (hydro)oxides.

Derivative voltammetry: a simple tool to probe reaction selectivity in photoelectrochemical cells

We demonstrate the use of a derivative voltammogram method to predict the selectivity of the photo-driven oxidation of 5-hydroxymethylfurfural (HMF) on a WO3 photoanode using only information obtained from the linear sweep voltammogram (LSV).

Soft template assisted hydrothermal synthesis of phosphorus doped porous carbon spheres with tunable microstructure as electrochemical nanozyme sensor for distinguishable detection of two flavonoids coupled with derivative voltammetry

• Phosphorus-doped hierarchically porous carbon nanosphere (PVP-P-PCS) was obtained. • PVP-P-PCS was prepared by soft template assisted hydrothermal method from xylan. • PVP-P-PCS possessed coexisted micropores, mesopores and macropores. • PVP-PCS showed intrinsic oxidase-like characteristic and high sensitivity. • Distinguishable detection of two flavonoids achieved with derivative voltammetry. A variety of phosphorus doped porous carbon spheres (P-PCSs) with tunable microstructure are facilely prepared by hydrothermal method using xylan as a carbon source, phosphoric acid as an activator and dopant, surfactants as soft templates. Surfactants are beneficial to the development of pore structure and the decrease of particle size. In particular, the introduction of polyvinylpyrrolidone (PVP) facilitates the formation of hierarchically porous structure and nanoscale dimension. The activation of phosphoric acid can improve the graphitization degree, enrich the surface oxygen-containing groups, realize phosphorus doping, and increase the specific surface area. The prepared PVP-P-PCS as a highly conducting electrocatalyst with well dispersed nano-sized spherical morphology of 50–150 nm, large specific surface area of 1558.14 m 2 /g and hierarchical porosity with coexisted micropores, mesopores and macropores, displays enhanced current responses of about 55-fold enhancement for luteolin and 52-fold enhancement for baicalin compared with bare GCE, intrinsic oxidase-like (nanozyme) characteristics, excellent electrocatalytic ability for luteolin with a low limit of detection (LOD) of 0.77 nM in linear ranges of 0.05–1 μΜ, and baicalin with a LOD of 3.3 nM in linear range of 0.05–1 μM. First-order derivative voltammetry is selected for realizing distinguishable determination of two flavonoids, which demonstrates satisfactory results in the practical application.

Revisiting glycerol electrooxidation by applying derivative voltammetry: From well-ordered bulk Pt to bimetallic nanoparticles

Metal nanoparticles are used to catalyze glycerol electrooxidation reaction aiming energy and chemical conversion, yielding carbonyl compounds with high market prices. The energy required to start glycerol electrooxidation is directly measured by the onset potential, determined by stationary voltammetry (dE/dt) in the form of a graph dj/dE (voltammogram). This topic has received much attention in recent years; however, a systematic rationalization of the methods to investigate the new nanomaterials is lacking to date. Here we target the identification of onset potential by revising glycerol electrooxidation on bulk well-ordered surfaces, Pt/C nanoparticles (NPs), and bimetallic NPs by applying derivative voltammetry (d2E/dt2). We revisit data regarding bulk Pt(111), Pt(110), Pt(100), and polycrystalline surface; FTIR in situ of isotopically labeled glycerol on bulk Pt and Pt/C; and concerning Sb-decorated Pt/C NPs. Our analysis shows that the use of conventional voltammetry may hide steps of the reaction and misguide the identification of the onset potential, which is accurately obtained by derivative voltammetry. The distortion induced on the function dj/dE created by an inappropriate current normalization method may disturb the threshold of the function, and the onset potential accordingly. This last point is critical since the catalyst may be mistakenly accepted as an active one.

Realising the activity benefits of Pt preferential (111) surfaces for ethanol oxidation in a nanowire electrocatalyst

The commercialisation of direct ethanol fuel cells (DEFCs) is hindered by the low activity of the currently available electrocatalysts that are mainly carbon-supported nanoparticles (NPs). Here, we synthesised carbon-supported Pt nanowires (Pt/C NWs) by chemical reduction of metallic precursors at room temperature without using surfactants, templates, or stabilising agents. The synthesised Pt NWs were supported on high surface area carbon (Vulcan XC-72 R) with 40 wt%. Of metal loading concerning the support. The electroactivity of the synthesised NWs catalyst towards ethanol and CO (the dominant intermediate species) oxidation is investigated and tested in comparison with a commercial nanoparticle Pt/C electrocatalyst (named: Pt/C NPs). The electrooxidation of ethanol was investigated in acid media by CO-stripping, cyclic voltammetry, derivative voltammetry, chronoamperometry, steady-state polarisation curves, and in situ Fourier transform infrared spectroscopy (FTIR) experiments. The results showed that the synthesised Pt NWs are much more active than the Pt/C NPs catalyst, for both ethanol and CO-monolayer oxidation in acidic media. In situ FTIR data revealed that Pt NWs catalyst favours the formation of CO2 and acetic acid. This activity is mainly due to the existence of extended terraces, resulting in enhanced mobility of OHads and COads, facilitating the removal of COads from the catalyst surface and allowing better ethanol adsorption for further oxidation. Hence, 5-fold higher current density for ethanol oxidation is obtained. The NW morphology of Pt nanocatalysts results in very active materials towards ethanol oxidation and may provide a promising means of increasing the performance of anodes for DEFCs.

Oxygen and SO2 Consumption of Different Enological Tannins in Relationship to Their Chemical and Electrochemical Characteristics.

The oxidative behavior of five commercial enological tannins of different sources (tea, grape marc, grape seed, untoasted oak, and toasted oak) was investigated in model wine solutions in the presence or absence of SO2. Solutions of the tannins were also analyzed for total phenolics, methyl cellulose precipitable tannins, high-performance liquid chromatography, and linear sweep voltammetry. Tea and oak-derived tannin solutions were characterized by the highest oxygen consumption rates, with oak-derived tannins exhibiting the highest oxygen consumption rates per milligram of phenolic material present. Linear sweep and derivative voltammetry parameters were well-correlated with oxygen consumption rates, whereas total phenolics or total tannins were not. All tannins were associated with consumption of SO2 upon reaction with oxygen, with the lowest rate of SO2 lost per milligram of O2 reacted being observed for oak tannins.

Carbon-Supported Pt and Pt–Ir Nanowires for Methanol Electro-Oxidation in Acidic Media

Direct methanol fuel cells are promising electrochemical energy conversion devices. But, more efficient and stable and less expensive catalysts are still required. Here, we successfully synthesized Pt/C and Pt0.5–Ir0.5/C, Pt0.6–Ir0.4/C, Pt0.7–Ir0.3/C, and Pt0.8–Ir0.2/C nanowires by the chemical reduction of the metallic precursors by formic acid and tested them towards methanol electro-oxidation in acidic media. Neither surfactants nor templates were used during the syntheses. The nanowires catalysts were compared with a commercial state-of-art catalyst aiming the observation of the properties improvements derived from both alloying Pt with Ir and morphology change from nanoparticles to nanowires. Well-defined and slightly agglomerated over the carbon nanowires (diameters and lengths of approximately 5 and 20 nm, respectively) were obtained, the fact that is ascribed to the 40 wt% metal loading. In addition, accelerated degradation tests showed that Pt0.6–Ir0.4/C, Pt0.7–Ir0.3/C and Pt0.8–Ir0.2/C catalysts are more stable than commercial Pt/C. All synthesized nanowires catalysts were more active towards methanol electro-oxidation than the commercial Pt/C. The Pt0.5–Ir0.5/C sample shows Pt mass activities 7 times that of commercial Pt/C. However, the Pt0.8–Ir0.2/C catalyst presented the best specific activity (6 times that of commercial Pt/C), have the highest currents in the derivative voltammetry and the oxidation potential shifts negatively 100 mV in comparison with the commercial Pt/C catalyst. Hence, the nanowires developed in this study are indicated as potential promising catalysts and can be applied successfully as direct methanol fuel cell anodes.

Application of derivative voltammetry in the quantitative determination of alloxan at single-walled carbon nanotubes modified electrode

Alloxan is a glucose analogue produced by the oxidation of uric acid and assumes physiological significance owing to its toxicity and diabetes inducing nature. Foods tainted with alloxan are considered as a leading cause of diabetes. Hence, real time quantification of alloxan is mandatory to estimate the diabetogenic risk of food samples. Electrochemical activity of alloxan at various carbon nanomaterials has been used for the quantitative determination of alloxan in neutral and acid media. This method has made use of derivative technique that does not require further instrumentation but has remarkably improved the sensitivity. Alloxan has exhibited the highest electrochemical activity at single-walled carbon nanotubes among the investigated carbon nanomaterials. The redox activity of alloxan has disappeared in the conventional voltammogram at a concentration of 3 × 10−6 M, whereas, prominent peaks have been observed well below 3 × 10−7 M in derivative voltammograms. Linear calibration graphs have been constructed in the concentration range between 3 × 10−3 and 3 × 10−7 M both in neutral and acid media. The detection limits of alloxan in neutral and acid media are 5 × 10−8 and 1 × 10−7 M respectively.

Highly active Pt3Rh/C nanoparticles towards ethanol electrooxidation. Influence of the catalyst structure

The electrochemical oxidation of ethanol results in the formation of strongly adsorbed intermediates. Pt–Rh catalysts are proposed as alternatives since they easy the CC bond breaking. However, the effect of the Pt–Rh structure on the catalytic activity and selectivity to CO2 is not well understood. Here, we synthesised Pt/C and two different Pt–Rh/C catalyst architectures, an alloy (Pt3Rh/C) and a bimetallic mixture (Pt3–Rh/C) to study the effect of catalyst structure on its catalytic activity and on the products formed during the ethanol oxidation in acid media. The nanoparticles were prepared by a modified polyol reduction method using ethylene glycol as a co-reducing agent and Pb as a material of sacrifice, to obtain very small and well-dispersed nanoparticles on the carbon support. Fourier transform infrared spectroscopy and derivative voltammetry was used to give insights about the ethanol oxidation mechanism occurring at the developed catalysts. The samples characterised by X-ray diffraction analysis showed distortions in the Pt lattice parameters for the Pt-Rh alloy structure due to the presence of Rh in the catalyst’s composition. Transmission electron microscopy analyses indicate that nanoparticles were well-dispersed on a carbon support, with spherical shapes and small particle sizes (2–3 nm). in situ X-ray absorption spectroscopy data evidence that Pt–Rh interactions produce changes in the Pt 5d band vacancy. The electronic effect is maximized when Pt forms an alloy with Rh, resulting in the highest d-band vacancy of the Pt3Rh/C. The Pt3Rh/C catalyst showed the highest activity towards ethanol oxidation, presenting current densities in a quasi-steady-state condition (measured at 600 mV) around 5.2 times higher than the commercial Pt/C (Alfa Aesar). Moreover, the onset potential for ethanol oxidation shifts to more negative potentials (110 mV lower taken at 1 mA cm–2) was also observed. In situ FTIR data revealed that Pt/C catalyst favours the formation of acetic acid. The synergistic effect between Rh and the alloy structure results in an easier CC bond breaking for Pt3Rh/C, in comparison to Pt3–Rh mixture, thus favouring CO2 formation at lower potentials.

Pt and Pt–Rh nanowires supported on carbon and SnO2:Sb nanoparticles for ethanol electrochemical oxidation in acidic media

Pt and Pt–Rh nanowires were successfully synthesized by chemical reduction with formic acid without any surfactants and were applied for the study of ethanol electrochemical oxidation in acidic media. The synthesis process lasted 72 h at room temperature and the nanowires were obtained with 40 wt% metal loading with respect to the carbon support. In addition, mixtures of carbon- and antimony-doped tin oxide were prepared and used as support in order to improve the catalytic activity and stability of the catalysts. Electrochemical activity was studied by cyclic voltammetry, chronoamperometry, and derivative voltammetry and the stability was tested by electrolysis at 0.6 V for 22 h. Physical characterization was carried out by X-ray diffraction, field emission gun scanning electron microscopy, and transmission electron microscopy. All Pt–Rh nanowires show higher activity than the commercial Pt/C catalyst towards ethanol oxidation. This feature is due to the fact that rhodium facilitates the cleavage of the C–C bond of the alcohol, resulting in higher oxidation efficiency. Physical characterization confirms the formation of nanowires that are widely dispersed on the supports, demonstrating the feasibility of the developed methodology for synthesis of Pt–Rh nanowires.

The Contribution of Carbon Supports on the Activity of Pt for Glycerol Electrooxidation: the Importance of Investigating the Derivative Voltammogram and Arrhenius Plots

Glycerol electrooxidation was evaluated on Pt electrodeposited over carbon Vulcan (CV), multi-walled carbon nanotubes (MWCNTs), graphene oxide nanoribbons (GONRs), and graphene nanoribbons (GNRs). Different masses of Pt were deposited under the same conditions, producing different surface areas of Pt. The presence of GNRs slightly enhanced the specific activity of the catalyst. By investigating the derivative voltammetry of glycerol, we found that the supports did not shift the onset potential towards lower values. Moreover, we found that the apparent activation energy did not vary by changing the carbon support. In this sense, we rationalized the slight improvement in specific activity of Pt deposited on GNRs as a consequence of the frequency of collision factor due to the availability of Pt over the longitudinal flat surface of nanoribbons, as shown by the high active surface area/mass of electrodeposited Pt ratio.

Rapid fingerprinting of white wine oxidizable fraction and classification of white wines using disposable screen printed sensors and derivative voltammetry

This work describes the application of disposable screen printed carbon paste sensors for the analysis of the main white wine oxidizable compounds as well as for the rapid fingerprinting and classification of white wines from different grape varieties. The response of individual white wine antioxidants such as flavanols, flavanol derivatives, phenolic acids, SO2 and ascorbic acid was first assessed in model wine. Analysis of commercial white wines gave voltammograms featuring two unresolved anodic waves corresponding to the oxidation of different compounds, mostly phenolic antioxidants. Calculation of the first order derivative of measured current vs. applied potential allowed resolving these two waves, highlighting the occurrence of several electrode processes corresponding to the oxidation of individual wine components. Through the application of Principal Component Analysis (PCA), derivative voltammograms were used to discriminate among wines of different varieties.

Voltammetric speciation studies of systems where the species diffusivities differ significantly

A rigorous and simple analytical solution is reported for the square scheme in single pulse techniques at (hemi)spherical electrodes when the electron transfers are reversible and the coupled chemical reactions are at equilibrium. The solution presented imposes no restriction to the values of the diffusion coefficients of the different species, and then it fully describes the cases where the coupled chemical processes involve significant changes of diffusivity. Simple criteria are discussed to understand and predict the effects of electrode radius, experiment time-scale and chemical thermodynamics on the results obtained in normal pulse voltammetry and derivative voltammetry. Unlike at macroelectrodes and ultramicroelectrodes, the position of the voltammograms (in these and other voltammetric techniques) is time dependent at spherical electrodes of intermediate size when the diffusion coefficients of the species are unequal. An analytical expression for the half-wave potential is given to describe this behaviour and also to assist the quantitative determination of the diffusion coefficients, formal potentials and equilibrium constants with the electrochemical techniques abovementioned.

Определение Ондансетрона На Угольно-Пастовом Электроде С Использованием Производной Вольтамперометрии

Определение Ондансетрона На Угольно-Пастовом Электроде С Использованием Производной Вольтамперометрии

Activity, short-term stability (poisoning tolerance) and durability of carbon supported Pt–Pr catalysts for ethanol oxidation

Pt–Pr/C electrocatalysts were prepared by a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation, their short term stability and durability were compared to that of commercial Pt/C and Pt–Sn/C (3:1) catalysts. By derivative voltammetry (DV) it was found that ethanol electro-oxidation takes place by two main pathways at different potentials. It was observed that, in the presence of Pr, ethanol electro-oxidation takes place mostly through the pathway at lower potential, which is the most interesting for fuel cell application. The Pt–Pr/C catalysts were less tolerant to poisoning by ethanol oxidation intermediate species than Pt/C. Durability test by a repetitive potential cycling under Ar atmosphere revealed a good structural stability of Pt–Pr/C catalysts. A repetitive potential cycling under CO atmosphere carried out on the Pt–Pr/C (1:1) catalyst, instead, indicated a structural change, likely by formation of a core–shell structure.

Sensitive determination of bisphenol A in plastic products by derivative voltammetry using an acetylene black paste electrode coated with salicylaldehyde-modified chitosan

A sensitive and reliable electrochemical method was developed for determination of bisphenol A (BPA) in plastic products using an acetylene black paste electrode coated with salicylaldehyde-modified chitosan (denoted as S-CHIT/ABPE). In the second-order derivative linear sweep voltammetry technique, BPA yielded a very sensitive and well-defined oxidation peak at 842 mV in 0.2 mol L−1 HCl solution. Owing to its unique structure and extraordinary properties, S-CHIT/ABPE showed higher accumulation efficiency toward BPA compared with bare ABPE, and significantly enhanced the oxidation peak current of BPA. Under the optimum conditions, the oxidation peak current was proportional to the concentration of BPA over the range of 4.0 × 10−8 mol L−1 ∼ 1.0 × 10−5 mol L−1. The detection limit (S/N = 3) was 2.0 × 10−8 mol L−1. The fabricated S-CHIT/ABPE not only exhibited strong adsorption capacity toward BPA, but also provided remarkable stable and quantitatively reproducible analytical performance. Additionally, this newly-developed method possesses some obvious advantages including high sensitivity, extreme simplicity, rapid response and low cost.

Outstanding electro-catalytic activity of Pt x –(RuO y –CeO2)1−x /C composites towards ethanol oxidation in acid media

Direct ethanol fuel cells are a key enabling technology for clean energy conversion; however, a major challenge is the determination of anode catalytic materials with high performance for complete ethanol oxidation. In this study, we synthesized binary Pt0.50–(CeO2)0.50/C and Pt0.50–(RuO y )0.50/C, as well as ternary Pt x –(RuO y –CeO2)1−x catalysts (x = 0.25, 0.50, or 0.75) and (y = 0, +2, or +3) by the sol–gel method and compared them in the ethanol oxidation reaction. Transmission electron microscopy images revealed the small particle size of the prepared catalysts (2.1–2.5 nm). Cyclic voltammetry, chronoamperometry, derivative voltammetry, and potentiostatic polarization were employed to analyze the ethanol oxidation reaction on binary Pt0.50–(CeO2)0.50/C and Pt0.50–(RuO y )0.50/C and ternary Pt x –(RuO y –CeO2)1−x catalysts, as well as Pt/C and Pt–Ru/C commercial catalysts, including some insights estimating a possible reaction mechanism. The results demonstrate, considering the activity outcomes approach, the highly superior performance of the Pt0.25–(RuO y –CeO2)0.75/C catalyst.

Glassy carbon electrodes modified with gold nanoparticles for the simultaneous determination of three food antioxidants

Electrochemical behavior of three antioxidants: butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and butylated hydroquinone (TBHQ), was investigated at a glassy carbon electrode modified with gold nanoparticles (AuNPs/GCE). This electrode was characterized by scanning electron microscopy (SEM). The experimental results indicated that the modified electrode was strongly electroactive during the redox reactions of BHA, BHT and TBHQ, and this was confirmed by the observed increased redox peak currents and shifted potentials; in addition, the oxidation products of BHA and TBHQ were found to be the same. The experimental conditions were optimized and the oxidation peaks of BHA and BHT were clearly separated. Based on this, an electrochemical method was researched and developed for the simultaneous determination of BHA, BHT and TBHQ in mixtures with the use of first derivative voltammetry; the linear concentration ranges were 0.10–1.50μgmL−1, 0.20–2.20μgmL−1 and 0.20–2.80μgmL−1, and detection limits were 0.039, 0.080 and 0.079μgmL−1, for BHA, BHT and TBHQ, respectively. The proposed method was successfully applied for the analysis of the three analytes in edible oil samples.