Electrooxidation Of Formaldehyde Research Articles

Formaldehyde electrochemical sensor using graphite paste-modified green synthesized zinc oxide nanoparticles

• The ZnO NPs were synthesized via green synthesis route. • The ZnO NPs have irregular sponge-like shapes. • The GPE/ZnO NPs electrode performed a faster electron transfer rate. • The GPE/ZnO NPs is more accessible than other formaldehyde analytical methods. • The GPE/ZnO NPs was employed in formaldehyde electrochemical sensor in tofu sample. The green synthesis route of metal oxide nanoparticles using plant derivative extract has attracted the attention of researchers due to the simplicity, low cost, use less chemical reagents, produce less toxic waste, as well ready conducted in ambient conditions. In this study, zinc oxide nanoparticles (ZnO NPs) were successfully prepared via the facile green synthesis route using orange ( Citrus sinensis ) peel waste aqueous extract (OPE) as the bio-complexing agent. The prepared ZnO NPs showed a broad Ultra-Violet (UV) peak at around 358 nm, indicating the significant excitation binding energy of the ZnO NPs. Further characterization using Fourier-transform infrared (FTIR) confirmed that flavonoids in the OPE play the primary role in nanoparticle formation. Moreover, the scanning electrode microscopy-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM) images showed that the prepared ZnO NPs have irregular sponge-like shapes, while the X-ray diffraction (XRD) confirmed the structure of ZnO was hexagonal wurtzite with a crystalline size of 11.58 nm. The electrochemical behavior study of the ZnO NPs-modified graphite paste electrode (GPE/ZnO NPs) using the ferro ferricyanide system was also performed, revealing that the ZnO NPs modification did not increase the mass transfer rate but successfully increased the electron transfer rate compared to the bare GPE. The cyclic voltammogram showed the optimum pH of 9 for the electrooxidation of formaldehyde (HCHO) on the GPE/ZnO NPs with an HCHO oxidation peak at 0.191 V vs. Ag/AgCl, while there was no reduction peak observed. Furthermore, in the phosphate buffer pH of 9 media, the linear correlation study between the square root of scan rate and the anodic peak current showed that the mass transfer of HCHO on the surface of GPE/ZnO NPs was mainly controlled by diffusion. The feasibility as the electrochemical sensor of HCHO is demonstrated by a limit of detection of less than 18 µM, linearity ranges from 0 to 100 mM, a ratio value of 0.38 of %relative standard deviation (RSD) to %RSD Horwitz, % recovery up to 103.9% in the real tofu sample, and the high selectivity toward HCHO instead of ethanol.

Highly Active Palladium-Decorated Reduced Graphene Oxides for Heterogeneous Catalysis and Electrocatalysis: Hydrogen Production from Formaldehyde and Electrochemical Formaldehyde Detection.

The exploitation of highly efficient and stable hydrogen generation from chemical storage of formaldehyde (FA) is of great significance to the sustainable development of the future. Moreover, developing an accurate, rapid, reliable, and cost-effective catalyst for electrochemical detection of FA in solution is appealing. Herein, we report rational construction of Pd nanoparticles decorated reduced graphene oxides (Pd/rGO) nanohybrids not only as robust catalysts to produce hydrogen from alkaline FA solution and but also electrocatalysts for electrochemical detection of FA. By optimizing the reaction parameters including FA concentration, NaOH concentration and reaction temperature, Pd/rGO with Pd loading of 0.5 wt% could exhibit a high hydrogen production rate of 272 mL g−1min−1 at room temperature of 25 °C, which is 3.2 times that of conventional Pd NPs. In addition, as-prepared Pd/rGO nanohybrids modified glassy carbon (GC) electrodes are used as FA-detected electrochemical sensors. A sensitive oxidation peak with a current density of 8.38 mA/cm2 was observed at 0.12 V (vs. Ag/AgCl) in 0.5 M NaOH containing 10 mM FA over Pd/rGO catalysts with Pd loading of 0.5 wt%. The results showed the prepared Pd/rGO nanocatalyst not only exhibited efficient and stable hydrogen production from alkaline FA solution but also had good electrocatalytic properties with respect to formaldehyde electrooxidation as a result of the synergistic effect of Pd NPs and rGO nanosheets.

Bimetallic nickel/manganese phosphate-carbon nanofiber electrocatalyst for the oxidation of formaldehyde in alkaline medium.

The development of earth-abundant transition metal-based catalysts, supported by a conductive carbonaceous matrix, has received great attention in the field of conversion of formaldehyde derivatives into toxic-free species. Herein, we report a comprehensive investigation of bimetallic electrocatalyst activity towards the electrooxidation of formaldehyde. The bimetallic phosphate catalyst is prepared by co-precipitation of Ni and Mn phosphate precursors using a simple reflux approach. Then the bimetallic catalyst is produced by mixing the Ni/Mn with carbon fibres (CNFs). The structural properties and crystallinity of the catalyst were investigated by using several techniques, such as scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Brunauer Emmett−Teller theory. The system performance was studied under potentiostatic conditions. Some theoretical thermodynamic and kinetic models were applied to assess the system performance. Accordingly, key electrochemical parameters, including surface coverage (Γ) of active species, charge transfer rate (ks), diffusion coefficient of the formaldehyde (D), and catalytic rate constant (kcat) were calculated at Γ = 1.690 × 10−4 mmol cm−2, ks = 1.0800 s−1, D = 1.185 × 10−3 cm2 s−1 and kcat = 1.08 × 105 cm3 mol−1 s−1. These findings demonstrate the intrinsic electrocatalytic activity of formaldehyde electrooxidation on nickel/manganese phosphate- CNFs in alkaline medium.

Cr‐Doped Pd Metallene Endows a Practical Formaldehyde Sensor New Limit and High Selectivity

AbstractElectrochemical sensors for detecting micromolecule organics are desirable for improving the perception of environmental quality and human health. However, currently, the electrochemical sensors for formaldehyde are substantially limited on the market due to the long‐term unsolved problems of the low electrooxidation efficiency and CO poisoning issue of commercial Pd catalysts. Here, a 2D Cr‐doped Pd metallene (Cr‐Pdene) with few atomic layers is shown as an advanced catalyst for ultrasensitive and selective sensing of formaldehyde via a highly efficient formaldehyde electrooxidation. It is found that the doping of Cr into Pd metallene can efficiently optimize the electronic structure of Pd and weaken the interaction between Pd and CO, providing an anti‐poisoning means to favor CO2 production and suppress CO adsorption. The Cr‐Pdene‐based electrochemical sensor exhibits one order of magnitude higher detection range and, especially, much higher anti‐interference for formaldehyde than that of the conventional sensors. Most importantly, it is demonstrated that the Cr‐Pdene can be integrated into commercializable wireless sensor networks or handheld instruments for promising applications relating to the environment, health, and food.

The Efficiency of the Electro-Oxidation of Small Organic Molecules: Oscillations and Mechanism

Many hydrogen-carriers have been considered for the direct use in fuel cells and also in the electrochemical reform, where they are oxidized instead of water at lower potentials. We have investigated the electro-oxidation of formaldehyde, formic acid, methanol, and ethanol,[1] and of ethylene glycol, glycerol, and glucose[2] on polycrystalline platinum in acidic media, and compare the activity under conventional and oscillatory regimes. The comparison is carried out by different means and generalized by the use of simple identical experimental conditions in all cases. The activity along slow potentiodynamic curves, inferred by the peak current, decreases in the following sequence: formaldehyde ~ formic acid > methanol > ethanol ~ ethylene glycol > glucose > glycerol. The ubiquitous occurrence of potential oscillations under galvanostatic regime is associated with excursions of the electrode potentials to lower values, which noticeably decreases the overpotential of the anodic reaction, when compared to that in the absence of oscillations. Considerable enhancement in the power density was observed in an idealized fuel cell operated with those fuels when operated under oscillatory regime. Furthermore, the spontaneous periodic self-cleaning processes, present important advantages to the use of autonomous oscillations to reach both higher and long-term activities, and stability [3]. The discussion of these half-cell studies is complemented with experiments with proton exchange membrane fuel cells, namely direct liquid fuel cells (DLFCs). We have investigated the effect of temperature on DLFCs under conventional and oscillatory conditions.[4] Methanol, formic acid, ethanol, and dimethyl ether (DME) were used as fuels and identical experimental conditions were used in all cases. Some findings observed in half-cells are also observed in the DLFCs studied, but few peculiarities of the experimental configuration adopted in the later arise. Finally, mechanistic aspects underlying the observed dynamics are discussed.[1] M. V. F. Delmonde, L. F. Sallum, N. Perini, E. R. Gonzalez, R. Schlögl, H. Varela, J. Phys. Chem. C 120 (2016) 22365.[2] G. B. Melle, T. A. Ferreira, R. L. Romano, H. Varela, in preparation (2020).[3] J. A. Nogueira, P. P. Lopes, N. M. Markovic, H. Varela, Electrochem. Commun. 121 (2020) 106853.[4] J.A. Nogueira, H. Varela, Energy Fuels 34 (2020) 12995.

Activated carbon and poly-o-anisidine(POA) synergistic supported Pt nanoparticles as a highly efficient catalyst for electrocatalytic oxidation of formaldehyde

In this work, different mass percentage of activated carbon (YBC) doped carbon paste electrodes (YBCPE) were firstly prepared, then electrodeposition of Pt nanoparticles was performed at a constant potential -0.1 V vs. Ag|AgCl|KCl (3 M) to prepare working electrodes Pt/YBCPE. It was shown that Pt/YBCPE(16%) exhibits the highest mass activity for formaldehyde oxidation compared to platinum deposited on pure carbon paste electrode (CPE) and other YBCPE(X%) electrodes. Afterwards, poly-o-anisidine (POA) film was prepared by electro-polymerization onto the CPE and YBCPE(16%) in o-anisidine monomer solution at 0.7 V and then Pt nanoparticles were electro-deposited at the POA film surface for fabrication of the Pt/POA/CPE and Pt/POA/YBCPE composite electrodes. The morphology of the composite electrodes was characterized by SEM, TEM, XRD and XPS which revealed that the presence of YBC and POA in the composite electrodes significantly improves the dispersion of Pt nanoparticles on the electrodes. Electrochemical impedance spectroscopy (EIS), chronoamperometry and cyclic voltammetry were used to verify the conductivity and durability of the composite electrode and its electro-catalytic activity. The obtained results indicated that the Pt/POA(16mC)/YBCPE(16%) exhibits excellent electro-catalytic activity towards the formaldehyde oxidation owing to the synergistic effect of the support-catalyst. Some comparisons for the electrooxidation of formaldehyde and the electrooxidation of methanol and formic acid on the composite electrodes also were conducted.

Oscillatory Reaction Rates in the Electro-Oxidation of Formaldehyde on Palladium

Formaldehyde has been used as a model system to investigate the electro-oxidation of small organic molecules, mainly on platinum[1]. This reaction is extremely dependent on the control conditions (potential and current) and it is also known to display self-organized oscillations on platinum[2]. In the present work we report a study of the oscillating reaction rates in the electro-oxidation of formaldehyde on polycrystalline palladium and in aqueous sulfuric acid media. The mapping of the existence region of potential oscillations was obtained by a slow current scan. Galvanodynamic oscillations were observed to range from 0.50 to 0.85 V. Further analysis was performed by galvanostatic measurements. The amplitude of potential oscillations increases in time. The potential-increase part of the cycle is formed by a rapid increase to about 0.60 V and then a slow one to 0.85 V, followed by an abrupt drop, with an average oscillation frequency of 0.15 Hz. Both the morphology and the frequency of oscillations differ from that observed for the electro-oxidation of formaldehyde on platinum, where the electrode potential varies from 0.40 to 0.90 V, and the it increases slowly until reaching 0.60 V followed by a rapid potential increase of up to 0.90 V, and then it decreases abruptly. Oscillations on platinum under comparable conditions were also about three times faster [3]. Overall, our results suggest the surface chemistry underlying the dynamics of formaldehyde elector-oxidation on palladium and platinum is considerably different, particularly under oscillatory regime. Some mechanistic aspects of the, far less studied, palladium system will be discussed.

In situ surface-doped PtNiCoRh nanocrystals promote electrooxidation of C1 fuels

Heteroatom-doped Pt-based nanocrystals have generated considerable interest and hold great prospects in heterocatalysis. However, engineering the superficial atomic configurations of these nanocrystals via in situ surface doping remains exceedingly challenging. Herein, we propose a one-pot, in situ surface doping chemical synthesis protocol to prepare quatermetallic PtNiCoRh dendritic nanocrystals as versatile and active catalysts for the electrooxidation of C1 fuels. Leveraging the selective coordination effect between ascorbic acid and Rh3+ ions, the doping of trace Rh atoms can be guided specifically at the near-surface of PtNiCoRh nanocatalysts. Electrocatalytic tests indicate that Pt67Ni16Co16Rh1 nanocrystals with in situ trace Rh-doped surface exhibit substantially enhanced activity, durability, and CO tolerance for the electrooxidation of methanol, formaldehyde, and formic acid. In situ Fourier transform infrared spectroscopy provides molecular-level insight into the exceptional performance of these nanocatalysts. The surface incorporation of anti-corrosive Rh atoms enables the transfer of CO intermediates from the atop Pt sites to the bridged Rh-Pt surface sites, thereby facilitating the elimination of these poisoning species from the catalyst surface. This study presents an effective in situ surface doping strategy which can enable the design of more atom-economic heterocatalysts.

Voltammetric Study of the Electrocatalytic Oxidation of Formaldehyde on Pt−Pd Co‐catalyst Supported on Reduced Graphene Oxide¶

AbstractElectrocatalysis on chemically converted graphene and decorated with Pt−Pd mixed‐catalyst (CCG/Pt−Pd) is described. Graphene sheets were chemically synthesizeed via microwave‐assisted method and modified with Pt−Pd mixed‐catalyst that was formed electrochemically. The hybrid layer, CCG/Pt−Pd displayed current oscillations for the electro‐oxidation of formaldehyde. Several factors influence both the number of oscillation in current peaks and their frequencies such as formaldehyde concentration, catalyst loading, potential scan rate and window, and temperature. CCG/Pt−Pd has high electrocatalytic activity toward formaldehyde conversion and increased oscillations were obtained at lower concentrations. Apparent activation energy for the oxidation process was Ea, of 6.29 kJ.mol−1.

Application of Cu/porous silicon nanocomposite screen printed sensor for the determination of formaldehyde

The copper–porous silicon (Cu/PS) nanostructure was synthesized by loading copper nanoparticles (CuNPs) on the etched PS through electroless deposition and characterized by various techniques. The electrocatalytic activity of the Cu/PS nanostructure modified screen printed carbon electrode (SPCE) was investigated for the electro oxidation of formaldehyde in alkaline media using cyclic voltammetry (CV). The modified electrode exhibits unique electrocatalytic activity for the oxidation of formaldehyde through an Electrochemical-Chemical (EC') pathway with 700 mV anodic shift toward negative potentials. Based on these results, a novel screen printed sensor for the determination of formaldehyde was developed. Due to oxidation of formaldehyde at very negative potentials, the hydrodynamic amperometric response of constructed nanosensor is very selective and linear from 0.4 mM to 4 mM of formaldehyde. The detection limit of amperometric method is 0.0124 µM. The catalytic response of proposed CuNPs/PS/SPCE for the oxidation of formaldehyde is very fast (less than 3 s), reproducible and stable. It was successfully applied as a new working electrode in amperometric determination of formaldehyde in water samples. This electrode can be used as a miniaturized sensor for the detection of formaldehyde at low concentrations.

Nanosized palladium loaded on porous ceria: A three-dimensional boosted electrocatalyst for electrooxidation of C1 compounds

The solution combustion synthesis was used for preparation of porous CeO2 with two different fuels; glucose and citric acid, for combustion. The samples of porous CeO2 are labeled as PCOGlu and PCOCit. The surface area of PCOCit and PCOGlu were estimated as 44.50 ± 0.12, and 47.72 ± 0.16 m2 g−1, respectively. The cavities acidity, OH groups on surface, and its bond strength to the active cerium sites are compared by measuring the pH of zero charges; that it was 11.95 ± 0.02, and 11.90 ± 0.03 for PCOCit and PCOGlu, respectively. The nanosized palladium (NPd) was loaded on PCOGlu and PCOCitvia wetness incorporation. As-prepared nano-microstructure electrocatalysts are utilized in the electrooxidation of C1 compounds, including methanol, formaldehyde, and formic acid. The NPd-PCOGlu presents higher electrocatalytic activity, stability and CO-tolerance ability for the electrooxidation of C1 compounds as compared to the NPd-PCOCit and NPd as non-supported palladium; So that, the performance of the modified electrodes increase in the order of NPd < NPd-PCOCit < NPd-PCOGlu. The PCO with porous structural network affected on the electrochemical surface area, dispersion, and durability of NPd. It is effective the capability of removing the poisoning species of the electrooxidation of C1 compounds on NPd through the lattice oxygen, and the activation of an oxidation−reduction cycle between the high and low chemical valences of cerium, leading to improve the electrocatalytic efficiency of NPd. Lastly, the conversion of methanol to formaldehyde, and then to formic acid during electrooxidation is confirmed by using cyclic voltammetry.

Palladium-polypyrrole composites as prospective catalysts for formaldehyde electrooxidation in alkaline solutions

Palladium-polypyrrole (Pd-PPy) composites synthesized via one-step and one-pot redox procedure have been tested as electrocatalysts for formaldehyde oxidation in aqueous solution under both inert and oxygen atmospheres. It has clearly been shown that inert electrode coated by the Pd-PPy composites demonstrates a high catalytic activity. Electrochemical response of Pd-PPy modified electrodes depends on the anodic potential range, pH and concentration of formaldehyde in solution as well as on the presence of oxygen in reaction atmosphere. It has been found that Pd-PPy composites are prospective materials for amperometric detection of formaldehyde in aqueous solution, even under oxygen atmosphere, as well as in the presence of methanol or/and formate-anions.

A catalyst coated electrode for electrochemical formaldehyde oxidation

Thermally prepared catalytic coatings on a titanium substrate were composed of a mixture of nanocrystals of metallic Pt and RuO2 of rutile structure and used for electrooxidation of formaldehyde. The size of the RuO2 nanocrystals increased, whereas those of Pt decreased with increasing the content of RuO2 in the mixture. At more positive potentials, the maximum catalytic activities showed the coatings with lower content of RuO2. Mechanism of formaldehyde oxidation was derived to show two reaction pathways. In the first one, H2C(OH)2 was directly oxidized to CO2, whereas COad was formed in the latter. COad is strongly adsorbed on Pt atoms, which causes blocking of these atoms and thus, preventing direct dehydrogenation of H2C(OH)2 to CO2. The overall catalytic effect of the mixture of nanocrystals was caused by the bifunctional mechanism. Thus, the Ru atoms formed the oxy species at more negative potentials than Pt. These oxy species oxidized the COad intermediates, bound to adjacent Pt atoms and accordingly, discharged them for dehydrogenation of new molecules of H2C(OH)2.

An efficient platform for the electrooxidation of formaldehyde based on amorphous NiWO4 nanoparticles modified electrode for fuel cells

We prepared a binary transition metal oxide material of nickel tungstate nanoparticles (NiWO4-NPs) through a simple co-precipitation method. The synthesized NPs were characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. NiWO4-NPs represent nearly spherical morphologies with an average size of ~97nm and tungstate as a dominant phase. Carbon paste electrode (CPE) modified with NiWO4-NPs (NiWO4-NPs/CPE) was used for electrooxidation of formaldehyde in alkaline solution. Cyclic voltammetry demonstrated that NiWO4-NPs/CPE electrode can decrease the overpotential for formaldehyde oxidation while increasing the current density in comparison to CPE. The results revealed that the CPE modified with calcined NiWO4-NPs (NiWO4-cal-NPs/CPE) shows less current response to formaldehyde oxidation compared with the amorphous sample. Moreover, the variation of scan rate and concentration of formaldehyde were investigated on the electrooxidation of formaldehyde and the results indicated that the electrooxidation on the NiWO4-NPs/CPE electrode is a diffusion-controlled mechanism. The diffusion coefficient and catalytic rate constant of formaldehyde, evaluated by chronoamperometry, were 40.4×10−4cm2s−1 and 1.37×104cm3mol−1s−1, respectively. Furthermore, we show that the prepared sensor has a wide linear range of 8μM to 1mM and low detection limit of 3.6μM.

Electroless copper deposition on epoxy glass substrate for electrocatalysis of formaldehyde

In this paper, we investigated the characteristics of a structured copper (Cu) film deposited on the surface of an insulating epoxy glass (EG) substrate via a facile electroless plating process. The film produced by this method was found to be of high purity and has a homogeneous microstructure consisting of an assembly of numerous aggregates that vary in size from 1 to 5 µm depending on the electroless deposition time. The electrocatalytic activity of the prepared electrode was investigated for the electrooxidation of formaldehyde using cyclic voltammetry in 0.1 M NaOH solution. Results show that formaldehyde oxidation takes place at a low potential of −0.34 V with large anodic current densities.

Selective Etching Induced Synthesis of Hollow Rh Nanospheres Electrocatalyst for Alcohol Oxidation Reactions.

The hollow noble metal nanostructures have attracted wide attention in catalysis/electrocatalysis. Here a two-step procedure for constructing hollow Rh nanospheres (Rh H-NSs) with clean surface is described. By selectively removing the surfactant and Au core of Au-core@Rh-shell nanostructures (Au@Rh NSs), the surface-cleaned Rh H-NSs are obtained, which contain abundant porous channels and large specific surface area. The as-prepared Rh H-NSs exhibit enhanced inherent activity for the methanol oxidation reaction (MOR) compared to state-of-the-art Pt nanoparticles in alkaline media. Further electrochemical experiments show that Rh H-NSs also have high activity for the electrooxidation of formaldehyde and formate (intermediate species in the course of the MOR) in alkaline media. Unfortunately, Rh H-NSs have low electrocatalytic activity for the ethanol and 1-propanol oxidation reactions in alkaline media. All electrochemical results indicate that the order of electrocatalytic activity of Rh H-NSs for alcohol oxidation reaction is methanol (C1 ) > ethanol (C2 ) > 1-propanol (C3 ). This work highlights the synthesis route of Rh hollow nanostructures, and indicates the promising application of Rh nanostructures in alkaline direct methanol fuel cells.

Sub-stoichiometric WO2.9 as co-catalyst with platinum for formaldehyde gas sensor with high sensitivity

The detection of formaldehyde (HCHO) in indoor environment is becoming more and more important. Here, a novel composites catalyst based on platinum and tungsten oxide was prepared for electro-oxidation of formaldehyde and used to design a simply equipped amperometric gas sensor. Considering that the modulation of atomic structure could effectively improve the properties of materials and enhance catalytic capability, we have regulated the local atomic structure of a commercial product of WO3 into the highly active sub-stoichiometric WO2.9 to be an efficient co-catalyst through a facile thermal treatment. Pt-WOX (X = 3, 2.9) nanocomposites were prepared by physical ultrasound and further characterized by XRD, XPS, TEM, SEM techniques. The electro-catalytic oxidation of formaldehyde at the Pt-WOX modified glassy carbon electrode was studied by cyclic voltammetry. Pt-WO2.9 (15%) exhibited better electrochemical activity with a higher oxidation peak current of 1.5 mA than that of Pt-WO3 (15%) and pure Pt. It is worth noting that reducing the platinum content in catalysts improves the catalytic activity. The Pt-WO2.9 based formaldehyde sensor displays a high sensitivity of 53 μA/ppm and good reproducibility and stability. Thanks to the tailored electronic structure (oxygen vacancies) of tungsten oxide, the as-prepared Pt-WO2.9 nanocomposites might become a promising candidate for practical application of detecting formaldehyde.

Nickel‐Palladium‐Based Electrochemical Sensor for Quantitative Detection of Formaldehyde

AbstractFormaldehyde is a small organic molecule that has a wide range of uses in society despite its toxicity. Formaldehyde is classified as a “known carcinogen” by International Agency for Research on Cancer (IARC). Formaldehyde electrooxidation has become a subject of major interest in the recent past due to its potential application in fuel cell technology and the need for its detection at trace levels because of its toxicity. Many studies have been conducted on formaldehyde electrooxidation, most of which suffer electrode passivation as a result of adsorbed intermediates such as carbon monoxide adsorbed (COads) and formic acid adsorbed (H2COOads) formed from electrooxidation of formaldehyde. In this study a Nickel Palladium nanoparticles modified glassy carbon electrode (Ni−Pd/GCE) was fabricated for electrooxidation of formaldehyde. Palladium nanoparticles were electrochemically deposited onto a bare Glassy Carbon Electrode (GCE) from 2 mM PdCl2 in 0.1 M H2SO4 supporting electrolyte, at a controlled potential of −0.14 V for 240 seconds. The Nickel nanoparticles were electrochemically deposited onto the PdGCE from 0.5 M NiSO4 in 0.1 M H2SO4 supporting electrolyte, at a controlled potential of −1.25 V for 40 seconds. The modified glassy carbon electrode (Ni−Pd/GCE) was conditioned in 0.5 M NaOH for about 50 cycles or more to obtain a reproducible voltammogram. The fabricated electrode was characterized using Cyclic Voltammetry (CV) and Chronoamperometry (CA). The results showed that the electrode had good electrocatalytic properties with respect to formaldehyde electrooxidation as a result of the synergistic effect of Ni and Pd nanoparticles combined with the glassy carbon technology. A sensitive oxidation peak for 1 mM formaldehyde was observed at about 0.43 V vs. Ag/AgCl/KCl (3 M) in 0.5 M NaOH, with a current density of 17 mA/cm2. It had a linear detection range from 10 μM to 1 mM (R=0.9985) and a detection limit of 5.4 μM. The electrode showed significant electrocatalytic activity towards the electrooxidation of formaldehyde in aqueous solution, was selective, reproducible and stable, hence can be used to detect formaldehyde at trace levels and can find application in fuel cells.

Synthesis and catalytic activity of Ag nanoparticles dispersed on nitrogen-doped GOPx toward direct electrooxidation of formaldehyde

Silver nanoparticles (Ag NPs) were synthesized and dispersed on the electronically conductive and electrochemically accessible surface of a GOPx composite, which was then employed as a probe for formaldehyde (HCHO) oxidation. The surface nanostructure, crystallographic properties, and oxidation state of the metal present in the GOPx-Ag nanocomposite were investigated using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. HCHO electrooxidation was evidenced by the appearance of a very well defined anodic peak with an onset potential of −0.783V, which is unique in the literature. The effect of various electroanalytical parameters like concentration, scan rate, and upper potential limit was investigated toward HCHO electrooxidation on GOPx-Ag catalyst. Amperometric study showed remarkable HCHO electrooxidation response with a wide linear range of 1μM–70mM, limit of detection (LOD) 0.167μM, limit of quantification (LOQ) 0.556μM and sensitivity of 35.74μAmM−1cm−2. The experimental results further indicated the long-term stability and practical feasibility of the GOPx-Ag catalyst, with excellent recoveries for HCHO oxidation. The remarkable catalytic efficiency and anti-poisoning properties were far superior to those of many previously reported HCHO sensors. The astonishing analytical performance of GOPx-Ag opens up a new path for fabricating promising HCHO sensors.

Fabrication of fine spongy nanoporous Ag-Au alloys with improved catalysis properties

Fine NP-AgAu (nanoporous AgAu) alloys with spongy structure was fabricated by chemical dealloying from rapidly solidified amorphous precursors Ag38.75−xCu38.75Si22.5Aux (x=0, 0.5, 1 and 5). The results indicate that the addition of small content Au in precursor can refine both the ligaments and pores obviously. Among the present components of the precursors, NP-AgAu alloys dealloying from Ag37.75Cu38.75Si22.5Au1 had the finest spongy structure. The size of pores was 5–10nm and the grain size of ligaments was 10–20nm. It also had the highest surface area of 106.83m2g−1 and the best catalytic activity towards electro-oxidation of formaldehyde with the peak current of 665mAmg−1.