Anodic characteristics of amorphous ternary palladium-phosphorus alloys containing ruthenium,rhodium, iridium,or platinum in a hot concentrated sodium chloride solution

Amorphous ternary palladium-based alloys containing platinum group metals as an additional element were prepared by rapid quenching from the molten state and their anodic characteristics were investigated in a 4 mol dm^?3 NaCl solution of pH 4 and 80° C. The amorphous alloys containing sufficient quantities of rhodium, platinum or iridium were passivated by anodic polarization and their corrosion rates at high current densities in the chlorine evolution region were extremely low. This fact was attributed to the formation of a highly protective passive film due to both the transformation to the amorphous structure and the addition of rhodium, platinum or indium. The electrocatalytic activities for chlorine evolution of amorphous alloys were higher than those of pure platinum group metals except palladium. In particular, the amorphous Pd₄₁Ir₄₀P₁₉ alloy had the desired stable, high electrocatalytic activity for chlorine evolution and the high overvoltage for oxygen evolution.     

Anodic characteristics of amorphous nickel-value metal alloys containing small amounts of platinum group elements in 0.5 M NaCl

By utilizing the characteristics of amorphous alloys capable of possessing specific electrocatalytic activity and corrosion resistance by alloying and surface activation treatment, an attempt was made to find amorphous alloys which are active as the anode material for production of sodium hypochlorite by electrolysis of seawater. Amorphous Ni-Nb and Ni-Ta alloys containing only 0.5–2.0 at % palladium and other platinum group metals showed a very high activity for chlorine production by electrolysis of 0.5M NaCl at 30°C when they were previously immersed in 46% HF for surface activation. The current efficiency of these surface-activated alloys for chlorine evolution considerably exceeded that of the currently used, most active Pt-Ir/Ti electrode for electrolysis of seawater. The surface activation treatment resulted in preferential dissolution of alloy constituents unnecessary for the electrocatalytic activity, i.e. nickel and valve metals, with a consequent enrichment of electrocatalytically active platinum group elements in the surface-activated layer. The corrosion weight loss of the surface-activated amorphous alloys under the steady state conditions for chlorine production was undetectable by a microbalance.     

The anodic polarization behavior of amorphous PdTiP alloys in NaCl solutions

The corrosion resistance and electrocatalytic activity for chlorine evolution of amorphous PdTiPalloys in NaCl solutions was investigated. Particular attention was given to the difference between amorphous and crystalline states and the effect of titanium addition. The corrosion rate of the amorphous alloys in the potential region for gas evolution was significantly lower than that of palladium over wide ranges of polarization potential and pH of solutions. This fact was attributed to the formation of a uniform passive film on the amorphous alloys and to the stabilization of passivity by the addition of titanium. The catalytic activity of the amorphous alloys for gas evolution was lower than that of palladium and decreased with an increase in titanium conten-t. The oxygen overvoltage of amorphous PdTiP alloys is considerably higher similarly to that of palladium     

An X-ray photoelectron spectroscopic study of electrocatalytic activity of platinum group metals for chlorine evolution

A correlation of the catalytic activity for anodic chlorine evolution of platinum group metals to the nature of the surface film formed during chlorine evolution in a sodium chloride solution was studied by X-ray photoelectron spectroscopy. The change in the surface film with increasing potential was found on platinum, including an increase in the cationic valence. This seemed responsible for the decrease in the activity for chlorine evolution on platinum in the high potential region. Increasing potential did not result in the appreciable increase in the cationic valence in the surface film on the other platinum group metals. Replacement of hydroxyl ions in the surface film by chloride ions became easier in the order of rhodium, iridium and palladium, and the activity for anodic chlorine evolution increased in this order due possibly to an increase in the amount of chloride ions in the film which seemed to be one of the reactants in the rate determining electrochemical desorption of adsorbed chlorine atom. Chlorine molecules adsorbed on the surface film were also found. It was assumed that the activity for anodic chlorine evolution might be low when the metal surface was covered by a large amount of molecular chlorine which was the reaction product.     

Electrochemical intercalation of aluminium chloride in graphite in the molten sodium chloroaluminate medium

Aluminium chloride intercalation in graphite was studied by anodic oxidation of compacted graphite (rod) and graphite powder electrodes in sodium chloroaluminate melt saturated with sodium chloride at 175 °C. The studies carried out by employing both galvanostatic and cyclic voltammetric techniques had shown that the intercalation reactions take place only beyond the chlorine evolution potential of +2.2 V vs. Al on both the electrodes. The extent of intercalation reaction was directly related to the anodic potential and probably to the amount of chlorine available on the graphite anodes. In the case of graphite powder electrode, a distinctly different redox process was observed at sub-chlorine evolution potentials and this was attributed to the adsorption of chlorine on its high surface area. This finding contradicts a report in the literature that the intercalation reactions occur at potentials below chlorine evolution in the chloroaluminate melt.     

Ultrafine Ni–Co–W–B amorphous alloys and their activities in benzene hydrogenation to cyclohexane

Quaternary Ni–Co–W–B amorphous alloys were prepared by chemical reduction of the aqueous solution of nickel and cobalt salts and sodium tungstate with potassium borohydride. The catalytic activities of the as-prepared materials were measured through liquid phase hydrogenation of benzene under moderate pressure. In comparison with Ni–Co–B, the as-prepared Ni–Co–W–B amorphous alloys showed superior activity, attributable to the promoting effect of tungsten on the microstructure of the alloys as revealed by XPS, XRD and DSC measurements.     

Kinetic factors in the chemical and electrochemical reactions including hydrogen on the first transition metals and cu-ni alloys

The relationships between catalytic activities (the rate of reaction of H₂-D₂ exchange, hydrogen evolution, hydrogen recombination, and para-hydrogen conversion), behaviour of hydrogen adsorption (amount of adsorbed hydrogen and initial heat of adsorption), and electronic properties of metals (work function, the percentage of the d-character and density of states at the Fermi level) are discussed. The catalytic activities were related to the amount of the strongly adsorbed hydrogen, which was estimated to be bounded by the 3d-band but not holes in the 3d-band in metals or alloys.     

Effect of cathodic reduction on catalytic activity of amorphous alloy electrodes for electrooxidation of sulfite

Active electrode materials for a new zinc electrowinning process, in which the thermodynamic cell voltage is about half that of the conventional process by replacing oxygen evolution by anodic oxidation of SO₂ produced in the zinc smelting process have been studied. Immersion in HF solution and subsequent cyclic voltammetry (CV) in sulfuric acid are known to be effective surface activation treatments of the amorphous alloy electrodes. The galvanostatic cathodic reduction (CR) treatment was applied to obtain further activation for sulfite oxidation for HF- and CV-treated electrodes prepared from amorphous nickel-valve metal-platinum group metal alloys. This treatment has been found to be effective in enhancing the activity. Among the amorphous Ni-40Nb alloys containing platinum group elements, the platinum-containing electrode showed the highest catalytic activity, which was higher than that of platinized platinum. Furthermore, the electrocatalytic activities of CR-treated electrodes prepared from amorphous alloys containing platinum and rhodium, and platinum and ruthenium were higher than that of the electrode containing only platinum. According to XPS analysis of the amorphous Ni-40Nb-1Pt-1Ru alloy specimen the enrichment of platinum and ruthenium occurred by CV treatment, and a small amount of oxidized platinum and ruthenium species remained on the electrode surfaces, but most of them were cathodically reduced to the metallic state by CR treatment. High catalytic activities for sulfite oxidation can be attributed to the metallic state of platinum and ruthenium contained in the alloy electrodes, even though the activity of these electrocatalysts is higher than that of pure Pt or Ru.     

Anodic behaviour of carbon materials in NaCl saturated NaAlCl4 fused electrolyte at low temperatures: A cyclic voltammetric study

The anodic behaviour of compacted graphite, graphite powder, glassy carbon and reticulated vitreous carbon electrodes in basic sodium chloroaluminate melt in the temperature range 428–573 K was studied using cyclic voltammetry. Chlorine evolution (> + 2.1 V vs Al) alone was the predominant reaction on the compact glassy carbon and fresh RVC electrodes. On compacted graphite, chlorine-assisted chloroaluminate intercalation was found to be a competitive process to the chlorine evolution. At high sweep rates, intercalation/deintercalation near the graphite lattice edges occur faster than chlorine evolution. Subsequent intercalation, however, is a slow process. Chlorine evolution predominates at higher temperatures and at higher anodic potentials. On graphite powders, a more reversible free radical chlorine adsorption/desorption process also occurs in the potential region below chlorine evolution. The process occurs at the grain boundaries, edges and defects of the graphite powder material. Intercalation/deintercalation processes are mainly responsible for the disintegration of graphitic materials in low-temperature chloroaluminate melts. Repeated intercalation/deintercalation cycles result in the irreversible transformation of the electrode surface and electrode characteristics. The surface area of the electrode is increased substantially on cycling. Electrode materials and operating conditions suitable for chlorine generation, intercalation/deintercalation and chlorine adsorption/desorption and power sources based on these processes are identified in this work.     

生物质燃烧过程中Cl及碱金属逸出的化学热力学平衡分析

采用化学热力学平衡分析方法,研究了秸秆、树皮、木屑、废木和橄榄渣5种生物质在400~1600 K温度范围和空气过剩系数分别为1.0, 1.2和1.4的燃烧条件下Cl及碱金属K和Na的化学平衡组成及浓度,讨论了其排放特性. 结果表明,空气过剩系数对生物质燃烧过程中Cl及碱金属K和Na的逸出影响较小;燃烧过程中含Cl组元主要以KCl(s), HCl(g), KCl(g), (KCl)2(g)和NaCl(g) 5种物质在800~1000 K温度范围进行固-气态转换;当燃烧温度大于850 K时,K和Na碱金属则主要生成KOH(g), KCl(g), (KCl)2(g), K2SO4(g), Na(g), NaOH(g), Na2SO4(g)和NaCl(g). 最大程度减少5种生物质在燃烧过程中含Cl及碱金属K和Na组元的产生和逸出量的最佳反应温度为850 K以下;高于900 K时,Cl及碱金属等气态物质则会大量生成.     

Simultaneous determination of chlorine and oxygen evolving at RuO2/Ti and RuO2–TiO2/Ti anodes by differential electrochemical mass spectroscopy

Chlorine and oxygen evolving at RuO2/Ti and RuO2–TiO2/Ti anodes have been simultaneously determined at electrode potentials from 1.0 to about 2V (vs Ag/AgCl) by differential electrochemical mass spectroscopy (DEMS). On the RuO2/Ti anodes, the threshold electrode potential for oxygen evolution increased with a decrease in RuO2 loading, while the chlorine evolution potential was unchanged. Low RuO2 loading anodes gave a high chlorine evolution ratio under various constant electrolysis potentials. On the RuO2–TiO2/Ti anodes, the threshold electrode potential for oxygen evolution increased with an increase in the TiO2 content more remarkably than that for chlorine evolution. High TiO2 content anodes gave a high chlorine evolution ratio at various constant electrolysis potentials. The combination of RuO2 and TiO2 exhibits a remarkable effect with respect to the enhancement of chlorine evolution selectivity.     

The anodic characteristics of the massive β-MnO2 doped with noble metals in sodium chloride solution

The anodic characteristics of the massive β-MnO₂ doped with a slight amount of noble metals were investigated in NaCl aqueous solution. The doping of noble metal, especially Pd, decreases the chlorine overvoltage enormously. By the kinetic considerations, it was clarified that noble metal sites dispersed on the oxide surface serve effectively as an active site for the chlorine evolution reaction. Furthermore, it was suggested that new effective catalysts for the chlorine evolution might be developed by using such noble metal-doped β-MnO₂ systems.     

The anodic evolution of oxygen and chlorine on foreign metal-doped SnO2 film electrodes

The anodic evolution of oxygen and chlorine on foreign metal-doped SnO₂ film electrodes were studied, in connection with their physical and chemical properties. In general, the anodic characteristics of noble metal-doped electrodes were much better than those of base metal-doped electrodes. The oxygen evolution reaction on noble metal-doped electrodes reflected each characteristic of the doped noble metals and the active center for this reaction was considered to be on the noble metal sites. On the other hand, the chlorine evolution reaction on such electrodes was found to be independent of the kind of doped noble metals and the probable mechanism for this reaction was proposed in which the spillover of Cl radical from noble metal to Sn sites was involved.     

Electrolytic oxygen evolution on Ni-Co-P alloys

Electrolytically obtained Ni–Co–P alloys exhibit amorphous structure. On heating these alloys to 773 K crystalline nickel and cobalt phosphide phases, and also nickel crystallites, are formed. After cathode-anode polarization of the amorphous and crystalline Ni–Co–P alloys in 5m KOH for 18 h, oxygen-cobalt compounds together with crystalline or amorphous nickel phosphides appear on the electrode surface. The evolution of oxygen from 5m KOH was studied on Ni–Co–P alloys prepared in this way. The Tafel parameters were determined and it was ascertained that the values of directional coefficients of the Tafel lines are comparable with those obtained for spinel NiCo₂O₄ oxides, while calculated values of the exchange currents for the oxygen evolution reaction are dependent on the chemical composition of the alloy. The rate of electrolytic oxygen evolution is virtually identical for amorphous and crystalline Ni–Co–P alloys of the same chemical composition. The highest rate of oxygen evolution was found for the alloy containing 15–20% Ni, 66–73% Co and 12–14% P.     

电沉积钼合金及其电催化性能

通过正交实验得到La-Co-Mo合金电沉积的最佳工艺条件。以DSA为阳极分别在钛基体上电沉积La-Mo、Co-Mo、La-Co-Mo合金,采用AES、电子测厚仪、显微硬度计、划痕实验、盐雾实验等手段对镀层性能进行测试。所得钼合金镀层致密、结合力强、耐高温腐蚀性能好。极化曲线测定结果显示,钛基体电沉积La-Mo、Co-M0、La-Co-Mo合金层析氢过电势比钛电极低,电催化性能高。钛基体电沉积钼合金层可望作为新型氯碱工业用高活性阴极。     

Electrochemical costripping models and mutual interferences of mutli-transition metal systems on the surface of boron-doped diamond

Electrochemical behaviors of electrodeposition stripping of some transition metals, such as Ag, Cu, Pb, Sn, and Cd were investigated on boron-doped diamond (BDD) film with differential pulse anodic stripping voltammetry (DPASV). The results show that the metal costripping process on the surface of BDD is influenced by deposition potential of transition metals, potential of hydrogen evolution reaction, mutual interferences between two transition metals, and so on. Electrochemical costripping models and mutual interferences of binary transition metals are proposed. (i) When the hydrogen evolution potential is higher or lower than the deposition potential of two transition metals, the metals do not form alloys and compound the cathode ions in the solution, and the costripping process conforms to metal 1 stripping-metal 2 stripping. (ii) When the hydrogen evolution potential is between the deposition potential of two transition metals, the metals do not form alloys and compound the cathode ions in the solution, and the costripping process conforms to metal 1 stripping-hydrogen evolution-metal 2 stripping. (iii) When two transition metals form alloys, the costripping process conforms to metal 1 stripping-alloy striping-metal 2 stripping. (iv) When the hydrogen evolution potential is between deposition potential of two transition metals, and transition metal 2 is complexed with one kind of cathode ion in the solution, the costripping process conforms to metal 1 stripping-hydrogen evolution-metal 2 complex formation-metal 2 stripping. Moreover, the electrochemical-costripping model of two transition metals in a solution with three or more transition metals, is similar to that in the binary system. It is also found that various metals electrodeposited on BDD film in the form of single metal or alloy can be completely stripped away by the constant-potential electrolysis technique at 2.8 V for 10 s.     

Disproportionation of CO on iron-cobalt alloys—II: Kinetic study on iron-cobalt alloys of different compositions

The catalytic activities in CO disproportionate of iron-cobalt alloys of various composition have been compared to the activities of the pure metals at 600°C using a $\text{C0}\text{C0}{}_2$ gas mixture (75% CO). The catalytic activities of the alloys are all greater than those of the pure metals. The synergetic effect is maximum for cobalt content between 37.5 and 50 wt %. These findings are consistent with a previous thermodynamic study which predicts that such compositions are the least liable to be poisoned by side reactions of carburization and oxidization. Furthermore X-ray diffraction studies show that contrary to pure metals the structures of the alloys are not modified by carbon deposition. The filamentous carbon deposit induces an important fragmentation of the metal catalyst originally under the form of coarse filings. The smallest particle sizes are obtained from the most active alloy composition.     

Structural evolutions and electrochemical behaviors of Co-B alloys as anode materials for alkaline secondary batteries

Co-B alloys were synthesized via a chemical reduction method, and adopted as anode materials for alkaline secondary batteries. The structural evolutions and the electrochemical behaviors of the as-prepared Co-B alloys with increasing heat-treating temperatures were analyzed with X-ray diffraction (XRD), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and charge-discharge test. It is found that the Co-B alloys treated at various temperatures show high reversibility. And the electrochemical activities were found to be dependent on the structural evolutions of the Co-B alloys. The amorphous Co-B alloy treated at 50 °C achieves an excellent discharge capacity of 304 mAh/g in the first cycle, while the Co-B alloy treated at 500 °C shows superior cyclicity.     

NaClO法合成二氯异氰尿酸钠工艺过程研究

二氯异氰尿酸钠是一种高效、安全、便于存储运输的固体含氯消毒品,采用NaClO法制备二氯异氰尿酸钠工艺流程相对简单,对设备腐蚀性小,该工艺特别适合建立在氯碱厂附近。通过实验研究,在低温下往NaOH溶液内通Cl₂制得高浓度NaClO溶液;将该NaClO溶液和氰尿酸于低温下通Cl₂反应,过滤所得的固体经真空干燥后可得w（有效氯）为62%的合格产品。     

Microstructure of new composite electrocatalyst and its anodic behavior for chlorine and oxygen evolution

The first layer of active coating made from a rutile-structured solid solution of ruthenium and titanium dioxides having an average crystal grain size of 30 nm was thermally deposited on an adequately prepared titanium metal substrate. Then, at a temperature of 500 °C, the second layer was formed on the first layer from a mixture of amorphous particles of metallic platinum and rutile-structured iridium dioxide nanocrystals having an average crystal grain size of 26 nm.Rutile phase nanocrystals are characterized by a high density of chaotically distributed dislocations and high internal microstrain values. The coatings exhibit a compact granular morphology without cracks on the surface. Their catalytic activity is similar to that of conventional DSAs for the anodic oxidation of chloride ions from both concentrated and dilute sodium chloride solutions. The anodic current efficiency both during chlorate formation and active chlorine production was several percentage points higher in electrolyzers containing these anodes than in those containing DSAs. The catalytic activity of anodes having these coatings is about 50 mV lower than that of DSAs and about 350 mV higher than that of lead/antimony alloy electrodes, for oxygen evolution from acid sulfate solutions (0.5 mol dm^?3 H₂SO₄) characteristic of processes for the production of some metals. An accelerated corrosion test showed that the stability of the double-layer anodes is about twelve-fold higher than that of conventional DSAs.