Anodic Oxidation Of Formaldehyde Research Articles

Multi‐Functional Formaldehyde‐Nitrate Batteries for Wastewater Refining, Electricity Generation, and Production of Ammonia and Formate

AbstractAs bulky pollutants in industrial and agricultural wastewater, nitrate and formaldehyde pose serious threats to the human health and ecosystem. Current purification technologies including chemical and bio‐/photo‐/electro‐chemical methods, are generally high‐cost, time‐consuming, or energy‐intensive. Here, we report a novel formaldehyde‐nitrate battery by pairing anodic formaldehyde oxidation with cathodic nitrate reduction, which simultaneously enables wastewater purification, electricity generation, and the production of high‐value‐added ammonia and formate. As a result, the formaldehyde‐nitrate battery remarkably exhibits an open‐circuit voltage of 0.75 V, a peak power density of 3.38 mW cm−2 and the yield rates of 32.7 mg h−1 cm−2 for ammonia and 889.4 mg h−1 cm−2 for formate. In a large‐scale formaldehyde‐nitrate battery (25 cm2), 99.9 % of nitrate and 99.8 % of formaldehyde are removed from simulated industrial wastewater and the electricity of 2.03 W⋅h per day is generated. Moreover, the design of such a multi‐functional battery is universally applicable to the coupling of NO3− or NO2− reduction with various aldehyde oxidization, paving a new avenue for wastewater purification and chemical manufacturing.

Multi-Functional Formaldehyde-Nitrate Batteries for Wastewater Refining, Electricity Generation, and Production of Ammonia and Formate.

As bulky pollutants in industrial and agricultural wastewater, nitrate and formaldehyde pose serious threats to the human health and ecosystem. Current purification technologies including chemical and bio-/photo-/electro-chemical methods, are generally high-cost, time-consuming, or energy-intensive. Here, we report a novel formaldehyde-nitrate battery by pairing anodic formaldehyde oxidation with cathodic nitrate reduction, which simultaneously enables wastewater purification, electricity generation, and the production of high-value-added ammonia and formate. As a result, the formaldehyde-nitrate battery remarkably exhibits an open-circuit voltage of 0.75 V, a peak power density of 3.38 mW cm-2 and the yield rates of 32.7 mg h-1 cm-2 for ammonia and 889.4 mg h-1 cm-2 for formate. In a large-scale formaldehyde-nitrate battery (25 cm2 ), 99.9 % of nitrate and 99.8 % of formaldehyde are removed from simulated industrial wastewater and the electricity of 2.03 W⋅h per day is generated. Moreover, the design of such a multi-functional battery is universally applicable to the coupling of NO3 - or NO2 - reduction with various aldehyde oxidization, paving a new avenue for wastewater purification and chemical manufacturing.

Realizing ampere-level CO2 electrolysis at low voltage over a woven network of few-atom-layer ultralong silverene nanobelts with ultrahigh aspect ratio by pairing with formaldehyde oxidation.

The development of advanced multi-functional electrocatalysts and their industrial operation on paired electrocatalysis systems presents a promising avenue for the gradual penetration of renewable energy into practical production. Herein, a self-supported conductive network of silverene nanobelts (Ag-ene NBs) was delicately assembled (Ag-NB-NWs), in which ultralong and few-atom-layer Ag-ene NBs with a high edge-to-facet ratio were interconnected, serving as "superreactors" for electron transfer and mass transport during the reaction. Such superstructures as electrocatalysts delivered an unparalleled performance toward the CO2-to-CO conversion with exclusively high faradaic efficiency (FE) and partial current densities of up to 1 A cm-2. Remarkably, the membrane electrode assembly (MEA) cell with Ag-NB-NWs as the cathode was capable of ultrastable and continuous operation for over 240 h at 0.4 A with ∼100% selectivity. More importantly, by further using Ag-NB-NWs as a bifunctional electrocatalyst, a record-low voltage overall CO2 electrolysis system coupling cathodic CO2 reduction with anodic formaldehyde oxidation in MEA cell was performed to achieve concurrent feed gas generation and formate production, substantially improving electrochemical techno-economic feasibility.

Coupling electrocatalytic cathodic nitrate reduction with anodic formaldehyde oxidation at ultra-low potential over Cu2O

An HCHO oxidation reaction for electrocatalytic ammonia synthesis was developed to replace the sluggish anodic oxygen evolution reaction involving electrocatalytic oxidative dehydrogenation and tandem reaction pathways.

Influence of Temperature on Peculiarities of Electroless Copper Deposition

The industrial electroless copper plating solutions containing formaldehyde as reducing agent are known from the middle of the last century and are widespread in the practice up to now. They are widely used in electronics for deposition of metallic copper layers on semiconductors or dielectrics (silicon wafers, resins etc.). Since such kind solutions are alkaline (formaldehyde is strong enough reducing agent for Cu(II) only in alkaline solutions), ligands are needed for preventimg of formation of Cu(OH)2 precipitate and binding Cu(II) into complexes Ethylenediaminetetraacetic acid (EDTA) is one of the most widely used ligand in alkaline electroless copper plating baths due to its perfect chelating properties. The possible solution equilibria in alkaline Cu(II)-EDTA-formaldehyde solutions are discussed in details. The data on use of EDTA in electroless copper plating as a Cu(II) ligand are enough wide-ranging, but, it is worth noting that practically all data are obtained at room or higher temperature. Therefore in this work copper coatings were deposited from alkaline formaldehyde-containing solutions, using EDTA as Cu(II) ligand at temperatures, mainly lower than room temperature. The experiments were carried out in electroless plating solutions at pH 12.0 - 13.0 and 5 - 30 °C temperature during 0.5 and 1h (Fig. 1). The thickness of the compact copper coatings obtained under optimal operating conditions in 1 h can reach ca. 4 μm, depending on the pH and temperature. The maximum values of plating rate are reaching at pH 12.5 at all investigated temperatures. The real surface areas (R f) of deposited copper coatings vary widely, i. e. from ca. 3.1 up to 39.3. The maximum R f values were obtained at pH 12.0 for investigated temperatures. The anodic formaldehyde oxidation measurements were carried out in formaldehyde solution at pH 12.5. It was found, that the rate of formaldehyde anodic oxidation depends on conditions of the formation of copper coatings – the highest rate of HCHO oxidation was determined on the surface’s electrolessly obtained at 5 °C and pH 13.0. Acknowledgment This research was funded by a Grant (No. LAT-12/2016) from the Research Council of Lithuania.

Nanoporous Pt Catalyst Modified by Sn Electrodeposition for Electrochemical Oxidation of Formaldehyde

AbstractA nanoporous Pt particles‐modified Ti (nanoPt/Ti) electrode was prepared through a simple hydrothermal method using aqueous H2PtCl6 as a precursor and formaldehyde as a reduction agent. The nanoPt/Ti electrode was then modified with limited amounts of tin particles generated by cyclic potential scans in the range of −0.20 to 0.50 V in a 0.01 mol·L−1 SnCl2 solution, to synthesize a Sn‐modified nanoporous Pt catalyst (Sn/nanoPt/Ti). Electroactivity of the nanoPt/Ti and Sn/nanoPt/Ti electrodes towards formaldehyde oxidation in a 0.5 mol·L−1 H2SO4 solution was evaluated by cyclic voltammetry and chronoamperometry. Electrooxidation of formaldehyde on the nanoPt/Ti electrode takes place at a potential of 0.45 V and then presents high anodic current densities due to the large real surface area of the nanoPt/Ti electrode. The formaldehyde oxidation rate is dramatically increased on the Sn/nanoPt/Ti electrode at the most negative potentials, where anodic formaldehyde oxidation is completely suppressed on the nanoPt/Ti electrode. Chronoamperogramms (CA) of the Sn/nanoPt/Ti electrode display stable and large quasi‐steady state current densities at more negative potential steps. Amperometric data obtained at a potential step of 100 mV show a linear dependence of the current density for formaldehyde oxidation upon formaldehyde concentration in the range of 0.003 to 0.1 mol·L−1 with a sensitivity of 59.29 mA·cm−2 (mol·L−1)−1. A detection limit of 0.506 mmol·L−1 formaldehyde was found. The superior electroactivity of the Sn/nanoPt/Ti electrode for formaldehyde oxidation can be illustrated by a so‐called bifunctional mechanism which is involved in the oxidation of poisoning adsorbed CO species via the surface reaction with OH adsorbed on neighboring Sn sites.

Silver Nanoparticles Supported on Ordered Mesoporous Carbon for Formaldehyde Electrooxidation

Metal nanocatalysts, as the anodic materials, have become increasingly important in fuel cells due to their unique physical and chemical properties. Here we report the ordered mesoporous carbon (CMK-3) supported silver nanocatalysts have been prepared through the wet chemical reduction by using the reduction of formaldehyde. The electrochemical properties of the Ag/CMK-3 nanocatalysts for formaldehyde oxidation are studied by cyclic voltammograms (CV) and chronoamperometric curves (i-t) in alkaline aqueous solutions. The results show that the peak current density (from CV) of the Ag/CMK-3 electrode is 112 mA cm-2, above 2 times higher than that of Ag/XC-72 at the same Ag loading (14.15 μg cm-2). Furthermore, the i-t curves demonstrate that the Ag/CMK-3 nanocatalysts are efficient and stable electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions. Our results indicate that the application potential of Ag/CMK-3 nanocatalysts with the improved electrocatalytic activity has far reaching effects on fuel cells and sensors.

Ag Catalyst on Ordered Mesoporous Carbon with High Electro-Oxidation Activity for Formaldehyde

Ag nanoparticles have been fabricated on the surface of CMK-3 mesoporous carbon through an immersion-electrodeposition (IE) technique. Transmission electron microscopy analysis indicated that it was a facile approach to electrochemically prepare nano-sized Ag clusters. Electrochemical experiments showed that Ag nanoproducts were efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions, and as the reduced of the potential value, the electrocatalytic peak current density for the formaldehyde electro-oxidation reaction was increased gradually. Also, the electrocatalytic activity of Ag/CMK-3 nanocatalysts for formaldehyde electro-oxidation is higher than that of Ag/XC-72 nanocatalysts. These findings represented a significant step toward the implementation of individual Ag/CMK-3 nanocatalysts as anodic materials in fuel cells and sensors.

Self-assembled silver nanoparticle films at an air–liquid interface and their applications in SERS and electrochemistry

In this paper, we present a novel technique to prepare silver nanoparticle films by controlling the self-assembly of nanoparticles at an air–liquid interface. In an ethanol–water phase, silver nanoparticles were prepared by reduction of AgNO 3 aqueous solution with NaBH 4 in the presence of cinnamic acid. It was found that the silver nanoparticles in this process could be trapped at the air–liquid interface to form 2-dimensional nanoparticle films. The morphology of nanoparticle films could be controlled by systematic variation of the experimental parameters. It is worth noting that the nanoparticle films could serve as the active substrates for surface-enhanced Raman scattering (SERS). 4-Aminothiophenol (4-ATP) molecule was used as a test probe to investigate the SERS sensitivity of different nanoparticle films. The results indicated that the nanoparticle films showed excellent Raman enhancement effect. Furthermore, the nanoparticle films prepared by our strategy were found to be efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline medium.

Electrooxidation of Formaldehyde on Silver/Ordered Mesoporous Carbon Composite Electrode in Alkaline Solutions

Metal nanocatalysts, as the anodic materials, have become increasingly important in fuel cells, due to their unique physical and chemical properties. Here, the porous silica was employed as a hard template to prepare the ordered mesoporous carbon (CMK-3). The as-prepared CMK-3 has a large surface area of 877 m 2 /g and the hierarchical porous structure with the pore size distribution centered at 3.7 nm. The CMK-3 supported silver nanocatalysts have been prepared through the wet chemical reduction by using the reduction of formaldehyde. The electrochemical properties of the Ag/CMK-3 nanocatalysts for formaldehyde oxidation are studied by cyclic voltammerry (CV) and chronoamperometric curves (i-t) in alkaline aqueous solutions. The results show that the peak current density (CV) of the Ag/CMK-3 electrode is 112 mA/cm 2 , above 2 times higher than that of Ag/XC-72 at the same Ag loading (14.15 μg/cm 2 ). Furthermore, i-t curves demonstrate that the Ag/CMK-3 nanocatalysts are efficient and stable electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions. Therefore, Ag/CMK-3 nanocatalysts with the improved electrocatalytic activity suggest their application potential towards fuel cells and sensors.

Potentiodynamic estimation of key parametric criterions and interrelating reversible spillover effects for electrochemical promotion

Electrocatalytic peaks from potentiodynamic spectra for relevant electrode reactions have been employed to assess decisive and most important diagnostic criterions and parameters in the electrochemical promotion of heterogeneous catalysts (EPOC) and electrocatalysts. More specifically, the anodic oxidation of formaldehyde by the spillover supplied primary oxide of Pt (Pt-OH), both of them proceeding simultaneously as the fast reversible electrode processes of rather high faradaic yields, was investigated to estimate the relevance of catalytic peaks in cyclic voltammetry for the electrochemical promotion. In the same sense, catalytic potentiodynamic peaks have been used to prove and assess the entire spillover (or effusion) effect both of H-adatoms and the primary oxide itself, too, otherwise decisive for some significant electrochemical oxidation processes, such as CO tolerance and kinetics in the cathodic oxygen reduction (ORR), including electrocatalytic features of the latter, as the one of most important electrode reactions in aqueous media. The UPD and OPD spillover double layer charging and discharging properties of the primary oxide (M-OH), interrelated with the interactive self-catalytic effect of dipole-oriented water molecules, has also been pointed out. There has also been inferred that altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/H x WO 3) under cathodic, and/or its hydrated state (Pt/W(OH) 6), responsible for Pt-OH effusion under anodic polarization, this way establishing reversibly revertible alterpolar features (Pt/H 0.35WO 3 ⇔ Pt/W(OH) 6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured type electrocatalysts, even of mixed hypo-d-oxide structure (Pt/H 0.35WO 3/TiO 2/C, Pt/H x NbO 3/TiO 2/C), have for the first time been synthesized by the sol–gel methods and shown rather high stability, distinctly pronounced electron conductivity and non-exchanged initial pure mono-bronze spillover and catalytic properties.

Morphology-dependent activity of silver nanostructures towards the electro-oxidation of formaldehyde

Morphological controlled silver nanoproducts have been prepared using the polyol process through varying the concentration of Na 2S. The relationship between the shape of Ag nanocatalyst and the activity for electro-oxidation of formaldehyde has also been investigated. The Ag nanoproducts were found to be efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions. Activity and selectivity were strongly dependent on the morphology of the silver nanoproducts. It was found that silver nanorods were more active than nanowires, nanopolyhedra and nanospheres.

Potential and current oscillations during formaldehyde oxidation on platinum particles dispersed in three-dimensional pore networks of TiO x/Ti

Electrochemical oscillations during the anodic oxidation of formaldehyde (HCHO) were studied on a modified electrode of platinum particles highly dispersed in the three-dimensional pore networks of TiO x /Ti (Pt-TiO x /Ti). Under conditions of room temperature and stationary electrode, not only current oscillations under both cyclic voltammetric and potentiostatic conditions but also potential oscillations under galvanostatic conditions were obtained. The intensity of current oscillations strongly depends on the concentration of HCHO or H 2SO 4, upper potential limit (upl) of cyclic voltammetry, applied constant potential and duration of time ( t d) at constant potential. Potential oscillations exhibit various patterns such as periodic, quasi-periodic, mixed-mode oscillations and other different bifurcations, which are greatly effected by the applied constant current and the concentration of HCHO or H 2SO 4. Meanwhile, the oscillatory system has a bistable characteristic with stable states at both low and high potentials. The observed potential and current oscillations are caused by the cyclic formation/removal of intermediate poison CO from the electrode surface during HCHO oxidation. The highly dispersed Pt particles on the surface of Pt-TiO x /Ti electrode improve the electrocatalytic activity of the electrode, which greatly facilitates the formation of CO by the oxidation of HCHO and the removal of CO by its reaction with hydroxyl radicals (OH). Furthermore, the three-dimensional pore networks of the electrode's TiO x /Ti support are favorable to the adsorption/desorption of reactants or intermediate product and thus increase the rate of reactions giving rise to electrochemical oscillations.

Sol−Gel Prepared Pt-Modified Oxide Layers: Synthesis, Characterization, and Electrocatalytic Activity

Thin films of pure RuO2 and IrO2 and mixed Ru0.5Ir0.5O2 oxide modified with Pt particles were prepared by a sol−gel method in the form of thin films of ∼2 μm thickness on Ti substrates. Surface morphology of these Pt-modified oxides was examined by scanning electron microscopy and was found to exhibit a significant influence of the chemical composition of the oxide matrix. Element mapping showed homogeneous distribution of the metals. X-ray diffraction and X-ray photoelectron spectroscopy analyses showed that these films consist of metallic Pt particles dispersed in an oxide matrix. Cyclic voltammetry in acid solutions showed that the sol−gel prepared layers have relatively high Pt surface areas. The electrocatalytic activity of these materials toward the anodic oxidation of formaldehyde and methanol was compared in terms of onset potential and current density and was found to follow the sequence: Pt−Ru0.5Ir0.5O2/Ti > Pt−RuO2/Ti > Pt−IrO2/Ti.

Accelerating effect of ammonia on electroless copper deposition in alkaline formaldehyde-containing solutions

The influence of ammonia on autocatalytic reduction of Cu(II) by formaldehyde (electroless copper plating) in solution containing Cu(II)–EDTA complex and additives (Na diethyldithiocarbamate and K4Fe(CN)6), was studied. Small additions of ammonia (1–3 mM) accelerated effectively the copper deposition at 20–30 °C by a factor of 2–4. In presence of ammonia copper layers of a higher real surface area (roughness factor Rf reached 22) and high electrocatalytic activity in anodic formaldehyde oxidation reaction were formed. The accelerating action of ammonia is explained by assuming that the copper surface of high catalytic activity forms at cathodic reduction of a mixed Cu(II) complex with EDTA and ammonia, and the liberated ammonia molecules participate again in the mixed complex formation at the copper surface.

Obtaining of high surface roughness copper deposits by electroless plating technique

The use of pyridine-2,6-dicarboxylic and 4-hydroxypyridine-2,6-dicarboxylic acids as copper(II) ligands in formaldehyde-containing alkaline electroless copper plating solutions allowed to obtain copper layers with extremely high surface roughness factor reaching approximately 120. The Cu deposits of higher surface area were formed at highly negative open-circuit (mixed) potentials; the correlation between copper electrode overpotential and roughness of the deposit was found and discussed. The copper films obtained demonstrate a high electrocatalytic activity in anodic formaldehyde oxidation process, the oxidation rate reaches 40 mA cm −2 and exceeds considerably that for other copper surfaces.

Silver nanostructured catalyst for modification of dielectrics surface

The preparation of nano-size Ag particles and their application for forming nanostructured catalysts on various surfaces are described. Silver colloid solutions were prepared by reduction of Ag(I) salt by tin(II) and characterized by electron microscopy, X-ray diffraction and light absorption spectra. Depending on the colloid preparation conditions metal particles of 5–100 nm size were obtained. According to XRD data, the colloid particles contain Ag and SnO 2 phases and no metallic Sn. The Ag nanoparticles were found to be efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions. The catalytic activity of a glassy carbon electrode with Ag surface coverage of 0.3–1 μg cm −2 is similar or even exceeds that of the metallic electrode. The silver particles were used for the initiation of the electroless copper deposition process on dielectrics; for that 1–2 μg cm −2 Ag is needed.

Anodic oxidation of formaldehyde on Pt-modified SnO 2 thin film electrodes prepared by a sol–gel method

Pt-modified SnO 2 electrodes were prepared onto titanium substrates in the form of thin films of ∼2 μm at different temperatures in the range from 200 to 400 °C. Surface morphology was examined by scanning electron microscopy (SEM). It was found that Pt–SnO 2 sol–gel layers are significantly rough and have a low porosity. X-ray diffraction (XRD) studies showed that the films consist of Pt nanoparticles with average size varying from about 5 to 10 nm, depending on the preparation temperature, and amorphous tin oxide. X-ray photoelectron spectroscopy (XPS) was employed to determine the superficial composition of the electrodes and demonstrated the presence of Sn 4+ in all the samples. XPS spectra of the Pt 4f electrons showed the presence of Pt in the zero-valence state as well as in ionic forms. The general electrochemical behavior was characterized by cyclic voltammetry in 1 mol l −1 HClO 4 and the electrocatalytic activity towards the oxidation of formaldehyde was investigated by potential sweeps and chronoamperometry. The results obtained show that the Pt−SnO 2/Ti system exhibits a significant catalytic activity for the oxidation of formaldehyde, with an onset potential below 0.1 V.

Modification of a Pt surface by spontaneous Sn deposition for electrocatalytic applications. 2. Oxidation of CO, formaldehyde, formic acid, and methanol

The electrocatalytic activity of a spontaneously tin-modified Pt catalyst, fabricated through a simple “dip-coating” method under open-circuit conditions and characterized using surface analysis methods, was studied in electrooxidation reactions of a preadsorbed CO monolayer and continuous oxidation of methanol, formic acid, and formaldehyde in the potentiodynamic and potentiostatic modes. The catalytic activity of the tin-modified Pt surface is compared with that of a polycrystalline Pt electrode. Spontaneously Sn-modified Pt catalyst shows a superior activity toward adsorbed CO oxidation and thus can be promising for PEFC applications. The methanol oxidation rate is not enhanced on the Sn-modified Pt surface, compared to the Pt electrode. Formic acid oxidation is enhanced in the low potential region on the Sn-modified surface, compared to the Pt electrode. The formaldehyde oxidation rate is dramatically increased by modifying tin species at the most negative potentials, where anodic formaldehyde oxidation is completely suppressed on the pure Pt electrode. The results are discussed in terms of poisoning CO intermediate formation resulting from dehydrogenation of organic molecules on Pt sites, and oxidation of poisoning adsorbed CO species via the surface reaction with OH adsorbed on neighboring Sn sites.

Sub-millimolar determination of formalin by pulsed amperometric detection

Formalin, formaldehyde in the presence of methanol, was determined by pulsed amperometric detection (PAD). A triple waveform using E det=−0.3 V ( t det=30 ms), E oxd=+0.8 V ( t oxd=200 ms), and E red=−0.8 V ( t red=350 ms) versus Ag/AgCl was applied at a Au electrode for detection in a flow injection (FI) system. The approach was rapid and yielded a sub-millimolar detection limit (0.0129 mM) with a dynamic range up to 100 mM. A precision of 8.8% R.S.D. at 1.0 mM for two hundred repetitive injections by the FI-PAD was obtained, whereas holding at a constant potential (−0.3 V versus Ag/AgCl) for anodic oxidation of formaldehyde caused the response to decrease dramatically after a few measurements. The method developed was used to analyze the formalin contents of water from rinsed samples of vegetables and fruit and ice-melt from seafood, and the method showed good agreement with the liquid chromatography (LC) method.