Continuous Cyclic Voltammetry Research Articles

Novel dynamic method based on CV-SECM and SWV-SECM for the in situ chemical imaging of reactive metal surfaces undergoing corrosion and corrosion inhibition illustrated with the case of copper corrosion inhibition by benzotriazole

A novel dynamic method for the chemical imaging of actively corroding metal surfaces using scanning electrochemical microscopy (SECM) is proposed by using CV-SECM and SWV-SECM. This consists of an adequate coupling of a repetitive voltammetric operation at the SECM tip while conducting the rastering routine for scanning a reactive copper surface, as well as its inhibition by benzotriazole. In this method, gold microelectrodes are employed as SECM tips, and therefore their electrochemical behaviour towards collection and redissolution of Cu2+ ions from synthetic solutions containing Cu2+ ions. Next, the dynamic application of voltammetric methods for the collection and stripping of copper on the Au probes while mapping copper surfaces was investigated. The proof of concept first involved continuous cyclic voltammetry (CV-SECM) in an acidified NaCl solution, in terms of Cu2+ dissolution and surface redox activity (with SECM in the feedback mode). Then, square wave voltammetry (SWV-SECM) was used to detect small copper dissolution from corroding and inhibitor-protected metal surfaces. The results are consistent with a heterogeneous nature of copper degradation and the development of protective films and passive layers.

Detection of acetone in the human breath as diabetes biomarker based on PPy/WO3 nanocomposite sensor by FFT continuous cyclic voltammetry method

AbstractThis research represents a novel detection method of acetone level in the exhaled breath samples (RH=88 %) based on polypyrrole/tungsten oxide (PPy/WO3) nanocomposite sensor. The PPy/WO3 sensor was fabricated by the deposition of nanocomposite on/between interdigitated electrodes (IDEs) through electrospray coating and was then characterized by FE‐SEM imaging. In this detection method, the coulometric signal of the sensor was calculated using Fast Fourier Continuous Cyclic Voltammetry (FFTCCV), where cyclic voltammetry (CV) was applied to the sensor in the defined potential rang and then charge changes of the sensor was obtained by integration of the current in all scanned potential ranges. FFTCCV method enhances the sensitivity of the sensor when exposed to the gas mixtures containing acetone. In addition to its fast coulometric response time (≤5 s) in the two linear ranges of 0.7–2.8 ppm and 2.8–28.2 ppm (R2=0.99), FFTCCV method provides the low detection limit of 70 ppb, and high sensitivity toward acetone at the optimum values of the parameters. The fabricated sensor showed great selectivity toward acetone when exposed to humid air and some exhaled gas like carbon dioxide, ammonia, methanol, ethanol and alkyl amines. The results were very satisfying as the sensor was capable to detect different acetone levels in human exhaled breath as non‐invasive diagnosis of diabetes with a good correlation (R2≃0.9) to the routine blood sugar test taken by different commercial glucometers results.

The effect of ultraviolet photocatalytic oxidation on ferrocyanide electrochemical behavior—An important factor in mediator-based electrochemical sensors

The ferrocyanide/ferricyanide (‘fcn’) ion is a redox-coupled molecule used frequently as an analysis and validation analyte in electrochemical and optical measurements, due to its stability and reversibility features. However, currently there are no studies of how fcn’s electrochemical properties are affected by irradiation photocatalysis. In this work we present, for the first time, a shift in the electrochemical properties of a fcn couple by executing a continuous cyclic voltammetry test under the influence of multiple irradiation wavelengths (UV, blue, yellow, and brightfield). UV wavelength irradiation led to a significant shift in the half-wave potential (Ehalf), converging to a new steady state. We suggested a thermodynamic model including ferrocyanide, ferricyanide, and an electrochemically non-active pentacyanoaquaferrate to describe the change in electrochemical behavior. Enriching one’s knowledge of a fcn electrochemical response to irradiation photocatalysis is crucial for electrochemical-optical experiments and may suggest its use for a stable UV detection test.

Study of catalase reversibility during multiple injections of H2O2 using online measurement by FFT continuous cyclic voltammetry

This work presents a new method for the determination of catalase activation reversibility upon injection of different concentrations of hydrogen peroxide (H2O2) based on fast Fourier transformation continuous cyclic voltammetry (FFTCCV). The spectroscopic and cyclic voltammetric data demonstrated that catalase could rapidly decompose H2O2 at concentrations below 40 mM. Also, the catalase activity gradually decreased at higher concentrations of H2O2. In addition, the calculated kinetics model of suicide inhibition demonstrated that the catalase irreversibility was triggered at the concentration of 80 mM. FFTCCV data by multiple injections of H2O2 revealed that the catalase activity could be recovered at 10, 20, 40, and 60 mM after 6, 4, 3, and 2 injections of H2O2, respectively. H2O2 at concentrations above 40 mM was not fully decomposed and remained in the solution after the catalase reaction. The maximum reversibility of the catalase activity was observed for the concentration of 10 mM, when H2O2 concentration drastically decreased within a few seconds of the reaction. Our data shows that the FFTCCV method can be recruited to monitor and evaluate enzymatic reactions.

Unprecedented facile approach of multiple amino-substituted triphenylamine derivatives for electrochromic devices with extremely high coloration efficiency and unexpected redox stability

Generally, the amino group is considered highly reactive and unstable. Thus, the amino derivatives would be entirely consumed by polymerization or end-capping to preserve the material stability in most research or application fields. Herein, we demonstrated that triphenylamine (TPA) with multiple para-amino substituents could reduce oxidation potential and provide extra oxidation sites while retaining their reversibility. Four para-amino-substituted TPA derivatives (TPA-1N, TPA-2N, TPA-3N, and TPA-ADM) designed and prepared in this study exhibited excellent stability under the electrochemical redox procedure, revealing more than 88% reversibility in the continuous cyclic voltammetry process up to 10,000 cycles. Among all the electrochromic devices, TPA-3N/HV performs the highest coloration efficiency (631 cm2/C), coloration speed (46.4 % s−1), and superior stability, manifesting a reversibility of 99% or 98% after 1000 cycles (switching) or 10 h (maintaining at coloring state), respectively.

Boron-Doped Diamond as a Quasi-Reference Electrode.

As a working electrode, boron-doped diamond (BDD) has been studied in detail in electrochemical processes because of its superior electrochemical properties. However, these characteristics have rarely been mentioned when BDD is used as a quasi-reference electrode (QRE). Herein, we conducted a systematic investigation on BDD electrodes, with different boron-doping levels (1 and 0.1%) and different surface terminations (hydrogen and oxygen) for their application as a QRE. A BDD electrode with 1% boron and a hydrogen-terminated surface achieved the best stability. Its open-circuit potential (OCP) exhibited less than 100 mV of potential drift over 6000 s and showed a minuscule half-wave potential difference (E1/2) of 0.0037 V in 0.1 mM K3[Fe(CN)6]/1 M KCl solution before and after the OCP measurement. Based on these observations, anions are found to contribute to the potential, which we preliminarily speculate as related to the capacitance caused by electrostatic adsorption on the positively charged hydrogen-terminated surface. The repeatability of measurement was verified through continuous cyclic voltammetry tests in 0.1 mM K3[Fe(CN)6]/1 M KCl, showing a maximum E1/2 difference of 0.042 V. The contribution of the redox couples was excluded, and the repeatability was considered to originate from its surface stability. Finally, a linear response of the optimized BDD as a QRE was validated (R2 > 0.99) by determination of free chlorine and dopamine concentrations, respectively. These results consolidate the existing fundamental research on BDD electrodes and promote the possibility of its application as a QRE in harsh environments or in vivo biological monitoring.

Synergized Ni/NiOx heterojunction encapsulated by N-doped graphitized carbon core@shell electrocatalyst for efficient hydrogen production

• Facile preparation strategy based on the self-assembly and in-suit synthesis. • The tunable composition of Ni/NiO x by optimizing calcination process. • Glycine as carbon and nitrogen sources to form N -doped carbon shell in one step. • The Ni/NiO x @NC electrocatalyst exhibits remarkable electrocatalytic performance. In this paper, based on the self-assembly of nickel glycinate, the Ni/NiO x heterojunction encapsulated by nitrogen-doped graphitized carbon shells (Ni/NiO x @NC) was prepared via two facile steps for hydrogen production. Attributed to the synergistic catalysis of the well-proportioned Ni/NiO x heterojunction, the accelerated electron transport and the protective effect of the NC layers, the prepared Ni/NiO x @NC catalysts exhibited good electrocatalytic performance, with a minimum overpotential of 173 mV (vs RHE) at the current density of 10 mA cm −2 in 1 M KOH and the slight performance degradation after continuous cyclic voltammetry sweeps for 6000 cycles.

Zn(II) porphyrin-based polymer facilitated electrochemical synthesis of green hydrogen peroxide

A polymer consisting of Zn(II) porphyrin (ZnP-polymer) is synthesized and characterized by various spectroscopic and microscopic techniques. The UV–Vis absorption spectrum proves that the ZnP-polymer possesses monomeric zinc porphyrin moieties. FT-IR spectral features and powder X-ray diffraction pattern support the successful synthesis of ZnP-polymer. Field emission scanning electron microscopy studies show the flake like structures of the synthesized ZnP-polymer. Atomic force microscopy reveals the surface roughness indicating the availability of catalytically active sites. The high-resolution transmission electron microscopy images show homogenously distributed elements and uniform morphology of ZnP-polymer. X-ray photoelectron spectroscopy further confirms the successful synthesis of ZnP-polymer with the characteristic deconvoluted bands of carbon, nitrogen, and zinc. The as-synthesized ZnP-polymer shows high selectivity towards the two-electron oxygen reduction reaction (ORR) and produces H2O2 selectively. It exhibits a high-positive onset potential (0.79 V) for the ORR in a basic medium with 72% H2O2 molar selectivity. In an acidic medium, the onset potential is 0.24 V with 50% H2O2 molar selectivity. ZnP-polymer shows high stability in both acidic and basic media with negligible change in onset potential/overpotential even after 3000 continuous cyclic voltammetry cycles and 7200 s amperometric response. The synthesized ZnP-polymer has the potential to be used as the ORR catalyst to synthesize industrial-scale green H2O2.

Enhancing quorum sensing in biofilm anode to improve biosensing of naphthenic acids

The feasibility of enhancing quorum sensing (QS) in anode biofilm to improve the quantifications of commercial naphthenic acid concentrations (9.4–94 mg/L) in a microbial electrochemical cell (MXC) based biosensor was demonstrated in this study. First, three calibration methods were systematically compared, and the charging-discharging operation was selected for further experiments due to its 71–227 folds higher electrical signal outputs than the continuous closed-circuit operation and cyclic voltammetry modes. Then, the addition of acylase (5 μg/L) as an exogenous QS autoinducer (acylase) was investigated, which further improved the biosensor's electrical signal output by ∼70%, as compared to the control (without acylase). The addition of acylase increased the relative expression of QS-associated genes (lasR, lasI, rhlR, rhlI, lasA, and luxR) by 7–100%, along with increased abundances of known electroactive bacterial genera, such as Geobacter (from 42% to 47%) and Desulfovibrio (from 6% to 11%). Furthermore, toxicities of different NAs concentrations measured with the Microtox bioassay test were correlated with corresponding electrical signals, indicating that MXC-biosensor can provide a dual platform for rapid assessment of both NA concentrations and NA-associated toxicity.

Composition engineered ternary copper chalcogenide alloyed counter electrodes for high-performance and stable quantum dot-sensitized solar cells

The rational design and development of economical, high-performance, and stable counter electrodes (CE) are critical to bringing the quantum dot-sensitized solar cell (QDSSCs) from the laboratory to a practical application. In this respect, we used a two-step approach to fabricate ternary copper chalcogenide (Cu 2−x S y Se 1−y ) alloyed semiconductors onto fluorine-doped tin oxide (FTO). In the first step, the binary copper chalcogenides CuS nanostructures that are synthesized using the microwave-irradiation technique are screen-printed onto the FTO substrate and annealed in a nitrogen atmosphere to obtain Cu 2−x S CE. In the second step, ternary Cu 2−x S y Se 1−y alloyed electrocatalyst is obtained through a composition engineering approach in which the elemental Se was incorporated on the surface of as-synthesized Cu 2−x S nanostructures using the drop-casting method. Compared to the pristine Cu 2−x S CE, the as-synthesized Cu 2−x S y Se 1−y CE has exhibited tunable crystal structures, compositions, morphologies. The electrochemical analysis revealed that the optimized Cu 2−x S y Se 1−y CE has exhibited low charge transfer resistance (R ct ), and excellent reduction activity to S n 2− species of the polysulfide electrolyte. Accordingly, QDSSCs assembled with Cu 2−x S y Se 1−y CE have delivered conversion efficiencies of 8.02%, which are higher than those of pristine Cu 2−x S CE (7.24%). Noticeably, Cu 2−x S y Se 1−y CE has demonstrated outstanding electrochemical stability in polysulfide redox couple , exhibiting no substantial fluctuations in either the current density or shape of the curve even after 200 continuous cyclic voltammetry (CV) cycles. Moreover, the best cell devices constructed using Cu 2−x S y Se 1−y CE validated remarkable stability under open-air conditions, retaining <60% of the original performance after 120 h of illumination. Overall, the ease of synthesis, low cost, time efficiency, and excellent electrocatalytic characteristics of the Cu 2−x S y Se 1−y alloyed semiconductors film demonstrated in this work make it an encouraging applicant for use as a CE material in photovoltaic applications. The two-step synthesis procedure of the ternary copper chalcogenide counter electrode. • Ternary copper chalcogenide (Cu 2−x S y Se 1−y ) alloyed electrocatalyst developed. • Cu 2−x S y Se 1−y exhibited compositions dependent tuneable crystal structures and surface morphologies. • Cu 2−x S y Se 1−y served as an efficient and stable counter electrode in the QDSSCs.

Redox reactions between ABTS•+ and dihydroxybenzenes as studied by cyclic voltammetry.

Redox reactions between several types of polyphenols and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+) used in a trolox equivalent antioxidant capacity (TEAC) assay were monitored by continuous cyclic voltammetry. The TEAC assay is one of the effective methods for clarifying the radical scavenging reaction mechanism of antioxidants. We obtained information on whether the reaction was a simple electron transfer, an electron transfer involving a subsequent chemical reaction of the antioxidant itself, or an electron transfer involving a coupling reaction between ABTS•+ and the antioxidant.

Environmental-friendly three-dimensional carbon nanotubes grown by soil clay and graphene oxide nanosheets for energy storage

Environmental-friendly three-dimensional (3D) multiwalled carbon nanotubes (CNTs) grown from the montmorillonite (MMT) and graphene oxide (GO) without adding metal catalysts are the first investigation for the supercapacitor electrode application, which dramatically reduces the noble and rare metal needs. Growth mechanisms of as-synthesized CNT-based MMTs (MCNTs) and CNT-based GOs- (GCNTs) via thermal chemical vapor deposition are suggested that the Ni ion nuclear seeds are self-arranged and intercalated spontaneously into the substrate surfaces and template layers. In addition, the maximum energy densities of MCNT and GCNT electrodes are 63.8 Wh/kg at 0.02 kW/kg and 147 Wh/kg at 0.09 kW/kg, respectively. The electrochemical impedance spectroscopy spectrum exhibits the charge transfer resistance significantly decreases with fabricating 3D active composite materials, indicating the mass transfer limitation in the low-frequency area and the charge transfer of kinetic controlling in the high-frequency domain. The Bode-phase angle at 78.6° of the GCNT electrode indicates ideal capacitive behavior. Frequencies of MCNT and GCNT electrodes at a phase angle of 45° are 0.27 and 0.11 Hz, corresponding to the calculated time relaxation constants of 3.70 and 9.09, respectively. MCNT and GCNT composites are clear to enhance a more surface accessible region for electrolyte ions and electron conductivity with the increasing CNT content. After 2000 continuous cyclic voltammetry and galvanostatic charge-discharge cyclic experiments, specific capacitance retentions with a 5% error bar of 3D MCNT and GCNT electrodes achieve 122.3 and 75.2%, 127.6 and 85.3%, respectively. As both electrodes, less metal usage is friendly to the environment, and in addition, layered fabrication is beneficial for production and further follow-up recycle separation of energy devices. Non-blending 3D MCNT and GCNT composites possess the potential to be the prospective materials for further energy storage application.

Self-sacrificial template synthesis of Fe, N co-doped porous carbon as efficient oxygen reduction electrocatalysts towards Zn-air battery application

Designing highly efficient non-precious based electrocatalysts for oxygen reduction reaction (ORR) is of significance for the rapid development of metal-air batteries. Herein, a hydrothermal-pyrolysis method is employed to fabricate Fe, N co-doped porous carbon materials as effective ORR electrocatalyst through adopting graphitic carbon nitride (g-C3N4) as both the self-sacrificial templates and N sources. The g-C3N4 provides a high concentration of unsaturated pyridine-type N to coordinate with iron to form Fe-N active sites. Through adjusting the Fe doping amounts, it is proved that appropriate Fe doping content is conducive to the construction of abundant defects and active sites of Fe-N. The as-prepared catalyst exhibits superior electrocatalytic ORR performance in alkaline media with half-wave potential (E1/2 = 0.82 V) and onset potential (Eonset = 0.95 V), equivalent to the commercial Pt/C catalyst. Moreover, there is almost no activity loss after 10 k continuous cyclic voltammetry cycles and methanol tolerance, indicating the excellent durability and superior methanol tolerance. Remarkably, when assembled as the cathode in a Zn-air battery, the device displays a power density of 99 mW/cm2, an open-circuit potential of 1.48 V and long-term discharge-charge cycling stability, indicating the promising potential to substitute the Pt catalyst for practical application.

Synthesis of flower-like cobalt, nickel phosphates grown on the surface of porous high entropy alloy for efficient oxygen evolution

The development of cheap, efficient and high activity non-noble-metal oxygen evolution reaction (OER) electrocatalysts is of great interest in promoting the application of water splitting. Herein, the flower-like phosphates were grown in situ on a porous microwave sintered CoCrFeNiMo high entropy alloy (HEA) by the hydrothermal–phosphorization method. The metal phosphates can promote the formation of hydroxides with high catalytic activity on the surface of the catalyst. The obtained porous HEA phosphates exhibit a low overpotential of 220 mV at 10 mA cm−2, a small Tafel slope of 30.3 mV dec−1 and superior stability in 1.0 M KOH. Especially, after continuous cyclic voltammetry (CV) 5000 cycles, the catalyst only requires the overpotential of 210 mV at 10 mA cm−2. The enhanced OER performance of this porous HEA is be attributed to 3D internal connected nanoporous structure, high conductivity, abundant metal (oxy)hydroxide nanosheets and the presence of phosphonates, that provides a sufficiently large surface exposure and allows the acceleration of the electron transfer rate between various species.

Sonochemical synthesis of Ag2WO4/RGO-based nanocomposite as a potential material for supercapacitors electrodes

The goal of this research is to synthesize a reduced graphene oxide/silver tungstate (Ag2WO4/RGO)-based nanocomposite by the incorporation of the Ag2WO4 nanoparticles into the RGO nanosheets through sonochemical method. The structural, chemical, and morphological properties of the prepared Ag2WO4/RGO nanocomposite were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) methods. The Ag2WO4/RGO nanocomposite was utilized as an efficient modifier for the supercapacitor electrodes. The electrochemical performance of Ag2WO4/RGO-based electrodes was investigated in 2 M H2SO4 solution by the electrochemical techniques such as continuous cyclic voltammetry (CCV), cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS). The Ag2WO4/RGO-based electrodes presented a specific capacitance of 534 F/g at the scan rate of 5 mV/s and energy density of 68 Wh/kg. CCV assessments of Ag2WO4/RGO-based electrodes showed exceptional cyclic stability (retention of 102.1% of its primary specific capacitance after 5000 cycles) and mechanical stability. The outstanding performance of the Ag2WO4/RGO nanocomposite revealed that it possesses the merits of both of Ag2WO4 nanoparticles and RGO nanosheets and confirms its suitability for the construction of the supercapacitors.

N-doped carbon nanoweb-supported Ni/NiO heterostructure as hybrid catalysts for hydrogen evolution reaction in an alkaline phase

The design of the cost-effective, efficient, and durable electrocatalysts for hydrogen evolution reaction (HER) is of great importance in the field of clean and renewable energies. In this study, Ni/NiO nanocomposite supported on N-doped carbon nanoweb (Ni/NiO/NCW) hybrid materials are proposed as an efficient electrocatalyst for HER in alkaline media. A series of Ni/NiO/NCW hybrid catalysts were prepared via polymerization of polypyrrole (PPy) in the presence of a surfactant, followed by incipient wetness impregnation and heat treatment techniques. The resulting Ni/NiO/NCW hybrid catalysts exhibit an excellent electrocatalytic properties with a lower overpotential of 105.3 mV (vs RHE) at 10 mA cm−2, a smaller value of Tafel slope (55.2 mV dec−1) and almost 100% Faradaic efficiency. It also shows good stability in performance attenuation during continuous cyclic voltammetry sweeps for 1000 cycles. Its excellent electrocatalytic performance for alkaline hydrogen evolution reaction can be attributed to the synergistic effect associated with the morphological benefit of 3D N-doped carbon nanoweb and Ni/NiO heterostructure with the optimal ratio of Ni to NiO.

Influence of temperature on the preparation of CoFe2O4 by the sol-gel method and its application in electrochemical energy storage

CoFe2O4 particles were successfully synthesized by a sol-gel proteic route in three different temperatures, and their structural and morphological properties were studied in detail. The XRD pattern results confirmed CoFe2O4 formation with some residual second phase of αCo–Fe in low temperature calcined materials. FTIR spectra showed the strong absorption bands in the range of 440 to 650 cm−1, which are related to Fe–O and Fe–Co bonds. SEM images illustrated that the cobalt ferrite particles exhibit a porous structure are formed by a hexagonal morphology. It was observed that the increase of calcination temperature resulted in more crystalline and better organized materials. CoFe2O4 specific capacity was 76.52 mA h g−1at current density of 1 Ag−1. This was the best result obtained with the 1000 °C material, which was based on the fact that temperature has a great influence on the electrochemical response of cobalt ferrite synthesized by proteic sol gel. It was also observed that 75% of the initial capacity remains the same for 5000 continuous cyclic voltammetry at the scan rate of 25 mVs−1which confirms the superior performance of the prepared electrode as energy storage material.

Altering the MOF-74 derivatives for efficient oxygen electrocatalysis through synergistic multi-metals and nitrogen modification

Herein, a novel method to employ a copper- and nitrogen-containing sodium copper chlorophyllin to couple with a cobalt- and zinc-based metal???organic framework-74 (CoxZn3???x-MOF-74) is intently developed. When the ratio between cobalt and zinc is 1:2 in the synthetic process, the final obtained cobalt and copper oxides supported by nitrogen-doped porous carbon catalyst at 900 ??C (CoCu/PNC-900) possess hierarchical porous structure with optimal microporous and mesoporous proportion. Besides, the heteroparticle CoCu/PNC-900 also preserves the framework structure of MOF-74 with open porous structure for the exposure of active metal sites and fast mass diffusion in reaction. The optimized conductivity, porosity and full utilization of multiple metals together provide the catalyst with robust electrocatalytic performance. For the catalysis of oxygen reduction reaction, CoCu/PNC-900 displays good electrocatalytic activity with half-wave potential of +???0.811 V (vs. RHE), falling only 19 mV behind commercial Pt/C catalyst (+???0.830 V vs. RHE) in 0.1 M KOH. Besides activity, CoCu/PNC-900 also shows noticeable stability with 12 mV of degradation after continuous cyclic voltammetry test of 5000 cycles. Furthermore, CoCu/PNC-900 shows 20 mV in potential close to that of IrO2 at 10 mA cm???2, indicating its decent catalytic activity for oxygen evolution reaction.

Rapid Electrochemical Ultra-Sensitive Evaluation and Determination of Daptomycin Based on Continuous Cyclic Voltammetry

Background: In this work, a novel and extra sensitive blood sample determination method for on-line monitoring of Daptomycin is represented. Materials and Methods: This technique is in accordance with the electro-membrane extraction (EME) and stripping fast Fourier transform continuous cyclic voltammetry (SFFTCCV) coupling. Briefly, the potential waveform had become constantly utilized over a Gold Electrode and the electrode impulse was acquired by taking away the base current and developing the current in the particular potential area of oxidation of sample. Results: This method was performed by utilizing a DC potential and migration of Daptomycin from the analyte fluid to the layer of 4-methyl-2-pentanol as well as following migration to the acceptor fluid. Conclusion: A low and valuable detection limit of 3.5 ng ml-1 and quantification limit of 10.2 ng ml-1 are considered as a part of the sensible results of this experiment. Furthermore, efficient linearity in the range of 10.0-600 ng ml-1 was observed.

Platinum nanoparticles on defect-rich nitrogen-doped hollow carbon as an efficient electrocatalyst for hydrogen evolution reactions.

Design and synthesis of efficient electrocatalysts with low usage of precious metal and of high stability are essential for their practical applications in hydrogen evolution reactions. In this work, we synthesize an electrocatalyst through the deposition of platinum nanoparticles on defect-rich nitrogen-doped hollow carbon derived from surface-attached poly(4-vinylpyridine) monolayers. The platinum nanoparticles with an average diameter of about 1.8 nm are well dispersed on the outer surface of the pre-synthesized carbon material and the platinum loading is about 8.6 wt%. The mass activity of the as-synthesized catalyst under an overpotential of 55 mV is about 5.0 A mgPt−1, about 4.93 times higher than that of commercial Pt/C catalysts. Moreover, the synthesized catalyst is also more electrochemically stable than commercial Pt/C catalysts as evidenced by continuous cyclic voltammetry and chronoamperometric response measurements.