Catalytic Oxidation Of Formic Acid Research Articles

N-doped hollow carbon nanospheres embedded in N-doped graphene loaded with palladium nanoparticles as an efficient electrocatalyst for formic acid oxidation

Efficient electrocatalysts with a low cost, high activity and good durability play a crucial role in the use of direct formic acid fuel cells. Pd nanoparticles supported on N-doped hollow carbon nanospheres (NHCNs) embedded in an assembly of N-doped graphene (NG) with a three-dimensional (3D) porous structure by a simple and economical method were investigated as direct formic acid fuel cell catalysts. Because of the unique porous configuration of interconnected layers doped with nitrogen atoms, the Pd/NHCN@NG catalyst with Pd nanoparticles has a large catalytic active surface area, superior electrocatalytic activity, a high steady-state current density, and a strong resistance to CO poisoning, far surpassing those of conventional Pd/C, Pd/NG, and Pd/NHCN catalysts for formic acid electrooxidation. When the HCN/GO mass ratio was 1:1, the Pd/NHCN@NG catalyst had an outstanding performance in the catalytic oxidation of formic acid, with an activity 4.21 times that of Pd/C. This work indicates a way to produce superior carbon-based support materials for electrocatalysts, which will be beneficial for the development of fuel cells.

Theoretical study of the oxidation of formic acid on a PtPd(111) surface

By performing density functional theory calculations, the adsorption configurations of formic acid and possible reaction pathway for HCOOH oxidation on PtPd(111) surface are located. Results show that CO2 is preferentially formed as the main product of the catalytic oxidation of formic acid. The formation of CO on the pure Pd surface could not possibly occur during formic acid decomposition on the PtPd(111) surface owing to the high reaction barrier. Therefore, no poisoning of catalyst would occur on the PtPd(111) surface. Our results indicate that the significantly increased catalytic activity of bimetallic PtPd catalyst towards HCOOH oxidation should be attributed to the reduction in poisoning by CO.

Metal–Polymer Nanocomposites with Carbon Fillers for the Catalytic Oxidation of Formic Acid

Metal–polymer Pt–Pd nanocomposites on a Nafion polymer membrane modified with carbon nanotubes and carbon black are synthesized by the chemical reduction of ions in aqueous organic solutions of reverse microemulsions. The functional characteristics of the nanocomposites are studied by cyclic voltammetry and atomic force microscopy. The synthesized nanocomposites exhibit strong catalytic activity in the formic acid oxidation reaction. It is found that, at the optimum ratio of platinum metals, the catalytic activity of the metal–polymer composites is higher than that of the carbon nanocomposites.

Revealing the key oxidative species generated by Pt-loaded metal oxides under dark and light conditions

The role of key oxidative species in formic acid oxidation using neat and platinum-loaded TiO2, CeO2 and SiO2 was investigated. The catalytic reactions under three different illumination conditions; dark catalysis (i.e. no illumination), dark catalysis with UV light pre-treatment (denoted as pre-30) and photocatalysis (i.e. continuous UV illumination), were studied. The activities of neat TiO2, CeO2 and SiO2 were low under dark and pre-30 conditions while under illumination (photocatalysis) the semiconductor metal oxides, TiO2 and CeO2 showed much higher oxidation rates. For the Pt-loaded catalysts, the key active species were surface active oxygen (PtOads and O−ads) under the dark catalytic condition with and without light pre-treatment while under photocatalytic condition, photogenerated holes and electrons are believed to form hydroxyl radicals (OH) and superoxide radicals (O2−), respectively, for CeO2, TiO2, Pt/TiO2 and Pt/CeO2. Unexpectedly, Pt/SiO2 showed the highest activity under the dark catalytic condition. The cuboctahedral shape of the Pt deposits on the SiO2 surface, which promote a greater number of sharp edges/corners at the interface, is believed to have been advantageous for dissociating and activating adsorbed oxygen species compared to the Pt deposits on TiO2 and CeO2. The Pt deposit shape is thought to be responsible for the observed high activity of Pt/SiO2 for the dark catalytic oxidation of formic acid.

Validation of Mixed Potential Theory Using Formic Acid and Ferric Ion As a Redox Couple

The present work explores the possibility of validating mixed potential theory using the redox reaction between formic acid with ferric sulphate (HCOOH + 2Fe3+ ⇋ CO2 + 2H+ + 2Fe2+) on platinum catalyst. It is hypothesized that the catalytic oxidation of formic acid by ferric sulphate can be viewed as two distinct electrochemical reactions proceeding simultaneously on the electrode, one being the electrochemical oxidation of formic acid and the other, electrochemical reduction of ferric ions. Moreover, for electroneutrality, the rate of oxidation of formic acid must match exactly with that of the reduction of ferric sulphate. The manifestation of this phenomenon is the unique electrode potential generally referred as the mixed potential. The value of the mixed potential can be determined easily by measuring the open circuit potential (OCP) of the electrode which is immersed in a solution containing both formic acid and ferric sulphate. Further, in the present work an attempt has been made to investigate the correlation between catalytic chemical reaction and the individual electrochemical halves in terms of conversion of ferric ions.The catalytic oxidation of formic acid by ferric sulphate was studied at rotating disk electrode on which platinum black catalyst was drop casted. The reaction was studied through open circuit potential (OCP) measurement (where no external electromotive force is applied) at different rotational rates of the electrode. The number of moles of ferric ions was determined spectroscopically over a period of five hours. It was observed that OCP increased with time due to decrease in the concentration of ferric ions. These experiments have been designated as chemical experiments. Simultaneously, the two electrochemical halves of the above redox reaction were studied independently at rotating disk electrode. Formic acid oxidation studies were performed through chronoamperometry and that of ferric ion reduction was studied via cyclic voltammetry technique. These sets of experiment are refereed as electrochemical experiments. From the electrochemical data obtained for reduction of ferric ions, key kinetic and transport parameter were determined and these were used further to model the current-voltage behavior for reduction of ferric ions to ferrous ions over time, assuming a first order reaction. Using this model in conjunction with OCP time data it was possible to predict the number of moles of ferric ion consumed as function of time during the OCP experiment. These predictions were compared with the number of moles of ferric ions actually consumed during OCP experiment. These comparisons were made at different rotation rates of the electrode and very good agreement between the measured and predicted values was observed at all rates of rotation. This validates the hypothesis that the kinetics of a catalytic chemical reaction can be obtained from the individual current potential relationship for the two electrochemical reactions.The present work suggests that catalytic chemical reactions follow an electron transfer mechanism. This approach would enable prediction of chemical kinetics for primarily catalytic reactions through few electrochemical parameters. Further, it opens up possibility of estimation of key electrochemical parameters for several catalytic systems and then the kinetics can be predicted by selecting the required parameters for corresponding oxidation as well as reduction reaction. Figure 1

Electrocatalytic Performance of Palladium Dendrites Deposited on Titania Nanotubes for Formic Acid Oxidation

AbstractPd catalyst with dendritic morphology was synthesized on ordered and uniformly distributed titania nanotubes (TNT/Ti), and bare Ti by a simple electrochemical deposition process. The influence of support morphology was studied in relation to Pd deposition and its electro catalytic oxidation of formic acid. The structural property of Pd dendrites was characterized by scanning electron microscopy and X‐ray diffraction. The electrochemical study showed the activity and durability of Pd/TNT/Ti catalyst for formic acid oxidation was enhanced compared to Pd/Ti electro catalyst. The synergetic contribution from TNT/Ti as support for Pd and its enhanced catalytic activity is discussed.

A nitrogen-doped graphene/gold nanoparticle/formate dehydrogenase bioanode for high power output membrane-less formic acid/O2 biofuel cells.

A high power output, membrane-less formic acid/O2 enzymatic biofuel cell was fabricated, in which nitrogen-doped graphene was proven to be effective for recycling the NAD(+)/NADH cofactor at a nitrogen-doped graphene/gold nanoparticle/formate dehydrogenase bioanode in the catalytic oxidation of formic acid.

Enhancing the catalytic oxidation capacity of Pt/TiO2 using a light pre-treatment approach

The role of UV light pre-treatment in enhancing Pt/TiO2 activity for the catalytic oxidation of formic acid in an aqueous environment and under ambient conditions has been examined. The impact of light pre-treatment, relaxation time (the period between light pre-treatment and formic acid addition) and re-illumination on the oxidation rate were considered. Pre-illuminating Pt/TiO2 provided an almost seven-fold increase in the formic acid oxidation rate compared with the untreated case. The oxidation rate decreased with increasing relaxation time, whereby after 16h of relaxation it had stabilised at a value still around three times greater than the untreated sample. Re-illuminating the Pt/TiO2 led to a complete recovery of the transient element of the activity. The Pt deposits were observed to undergo partial oxidation over the course of the reaction and, when coupled with a lower activity being observed upon purging the system with N2, imply the participation of dissolved oxygen in the overall oxidation mechanism. The findings suggest the platinum deposits can inject electrons into adsorbed molecular oxygen where the oxygen remains in an active state ready for oxidising the formic acid. Pre-treating the catalyst with light accentuates this effect as additional photogenerated electrons are drawn into the Pt deposits from the TiO2 and transferred to and held by the adsorbed oxygen. Striking features of this particular system is the light pre-treatment effect prevails for an unexpectedly long period (in the order of hours) and is completely recoverable with re-illumination.

Catalytic oxidation of formic acid by dioxygen with an organoiridium complex

Catalytic oxidation of formic acid by dioxygen occurred efficiently using an organoiridium complex as a catalyst in a water-containing organic solvent as well as in water at ambient temperature.

Functionalized Graphene Supported Pd Catalyst for Catalytic Oxidation of Formic Acid

In this work,the surface of GO was functionalized by different method and used to load noble metal Pd.It is found that the surface modification of GO can effectively enhance the loading amount of Pd and reduce the Pd agglomeration on the support surface,and thereby improve the catalytic activity of Pd-based catalyst for oxidation of formic acid.The activity of Pd-based electrocatalyst toward the oxygen reductionreaction(ORR) was examined using cyclic voltammetry through roating-disk electrode measurements in0.5 mol/L H2SO4electrolyte.Under the same experimental conditions,the loading amount and the catalytic performance of Pd on graphene oxide(GO),reduced graphene oxide(RGO) and sulfonated graphene(SGO)were studied.The results show that SGO is easier to load Pd and the obtained composite catalyst for CO tolerance is also improved significantly,which may be due to the synergetic effect from the π-π bonding of graphene and the van der Waals interactions of the —SO3H functionality,enhancing the loading and dispersion of Pd on the supporting materials effectively.

Synthesis of spherical porous Pd nanoparticle superstructure and its catalytic oxidation of formic acid

Spherical porous Pd nanoparticle superstructures with the diameter in the range of 30-50 nm were obtained by the reaction of PdCl₄^2- with hydrazine using hexadecylpyridinium chloride as a structure-directing agent in the mixed acetone/water solution. It was found that hexadecylpyridinium chloride had significant influence on the formation of the spherical porous Pd nanoparticle superstructure. Only solid spherical structure was formed in the absence of the surfactant. In addition, acetone had an effect on the size of the micelles modified. The electrocatalytic activity of the spherical porous Pd nanoparticle superstructure electrode for the formic acid oxidation in 0.5 mol/L H₂SO₄+0.5 mol/L HCOOH was also investigated. The results displayed that electrocatalytic activity and stability of the spherical porous Pd nanoparticle superstructure catalyst were better than that of the solid Pd catalyst.

A novel structural design of CNx-Fe3O4 as support to immobilize Pd for catalytic oxidation of formic acid

State Natural Science Foundation of China[21163018]; Post-doctoral Science Foundation of China[20110490847]; Northwest Normal University[NWNU-kjcxgc-03-63]

Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid

Small and highly dispersed palladium nanoparticles supported on graphene nanosheets were fabricated via a strategy of etching a copper template with Pd(2+). The obtained hybrid exhibited significant catalytic activity for formic acid oxidation.

Temperature (Over)Compensation in an Oscillatory Surface Reaction

Biological rhythms are regulated by homeostatic mechanisms that assure that physiological clocks function reliably independent of temperature changes in the environment. Temperature compensation, the independence of the oscillatory period on temperature, is known to play a central role in many biological rhythms, but it is rather rare in chemical oscillators. We study the influence of temperature on the oscillatory dynamics during the catalytic oxidation of formic acid on a polycrystalline platinum electrode. The experiments are performed at five temperatures from 5 to 25 °C, and the oscillations are studied under galvanostatic control. Under oscillatory conditions, only non-Arrhenius behavior is observed. Overcompensation with temperature coefficient (q(10), defined as the ratio between the rate constants at temperature T + 10 °C and at T) < 1 is found in most cases, except that temperature compensation with q(10) ≈ 1 predominates at high applied currents. The behavior of the period and the amplitude result from a complex interplay between temperature and applied current or, equivalently, the distance from thermodynamic equilibrium. High, positive apparent activation energies were obtained under voltammetric, nonoscillatory conditions, which implies that the non-Arrhenius behavior observed under oscillatory conditions results from the interplay among reaction steps rather than from a weak temperature dependence of the individual steps.

Galvanostatic and pulse potential synthesis of poly-3-methylthiophene. Polymer as catalytic support

Poly-3-methylthiophene (P3MT) films were electropolymerised on graphite and indium tin oxide electrodes and characterised by cyclic voltammetry and scanning electron microscopy. The polymerisation was carried out by two different techniques, pulse potential program and constant current density, yielding conducting coated polymeric electrodes. The polymeric films display structural differences depending on the polymerisation method. The conducting properties of the polymers also depend on the electropolymerisation method. Polymeric resistance and stability were studied.P3MT was used as a support for the anchoring of Pt and Pb metal particles. The catalytic oxidation of formic acid was studied with these electrodes and compared with that obtained with graphite/Pt massive electrodes.

Catalytic oxidation of formic acid in aqueous suspensions of platinized titanium dioxide

The kinetics of the oxidation of methanol, formaldehyde and formic acid in sulphuric acid by vanadium(IV) ions have been followed spectrophotometrically. As catalyst a platinum/titanium dioxide system has been used. The methanol and formaldehyde reactions were hindered by the appearance of a slowly reacting intermediate on the catalyst surface. Contrary to this, the catalyst was only slightly affected when exposed to formic acid, and the oxidation reaction followed almost a first-order reaction. From the appearance of the kinetic curves in the first two cases it was possible to deduce the structure of the slowly reacting intermediate (HCOC), indicating that exactly 1.4 electrons per site are required for its complete oxidation.