Additives nickel hydroxides

Nickel hydroxides have been used as the active material in the positive electrodes of several alkaline batteries for over century [1], These materials continue to attract much attention because of the commercial importance of nickel-cadmium and nickel-metal hydride batteries. In addition to being the cathode active material in nickel-metal hydride batteries, Ni(OH)2 is an important corrosion product of the anode during cycling. There are several reviews of work in the field [2-10],... 

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

P(0)(0Me)H and [TpAr Me]Zn0P(0)(0R)2, respectively (Scheme 26) (35). In addition, [TpAr Me]ZnOH also cleaves activated esters and amides in a stoichiometric fashion, as illustrated in Scheme 27. Kitajima has described a similar amide cleavage reaction between the copper and nickel hydroxide complexes [Tp JMtOH) (M = Ni, Cu) and p-nitroacetanilide to give [TpPr 2]M p2-MeC(0)NC6H4N02 [Eq. (34)] (198). 

With acetone and hydrogen chloride, cyanoguanidine forms the addition compound II this jdelds melamine on treatment with alkalis at room temperature, cyanamide being eliminated. In the presence of copper or nickel hydroxide, an intermediate cyanobiguanide-complex salt can be isolated, and converted by dilute nitric acid at 20° into cyanobiguanide... 

However, it can undergo self-reductive dissolution (loss of active material) accompanied by oxygen evolution [349]. The active material of the positive electrode (in pocket plate cells) consists of nickel hydroxide mixed with small additions of cobalt and barium hydroxides to improve the capacity and charging/discharging performance and graphite to improve conductivity [348]. 

Hexammino-nickel Chloride, [Ni(NH3)6]Cl2.—Nickel chloride absorbs ammonia gas at ordinary temperature. Rise in temperature occurs and increase in volume. The hexammine is best prepared, however, from an aqueous solution of the salt, as when prepared from the dry salt and ammonia gas it is exceedingly bulky. Aqueous ammonia is added to a solution of pure nickel chloride until the nickel hydroxide first precipitated is almost dissolved. The liquid is filtered and a saturated aqueous solution of ammonium chloride containing ammonia added, and air drawn through the liquid. On the addition of a further quantity of ammonium chloride a precipitate forms, which is collected, washed with ammonium chloride and ammonia, and finally with alcohol containing ammonia. 

This is the mechanism of an indirect electrolysis, where the nickel oxide hydroxide acts as an electrocatalyst that is continuously renewed. Some observations, however, are not consistent with this mechanism. The addition of an oxidizable alcohol should lead to an increase of the current for the nickel hydroxide oxidation and a decrease for its reduction This is not the case. The currents for nickel hydroxide and nickel oxide hydroxide remain unchanged, whilst at more anodic potential a new peak for the alcohol oxidation appears. This problem has also been addressed by Vertes... 

The benzoylhydrazone of benzaldehyde (57) is oxidatively cyclized at the nickel hydroxide electrode (0.1 M NaOH, 30% t-butanol 70 % water) to the oxadiazole 58, however in only moderate yield (22%). Main product is benzoic acid (59) (60%) additionally a nickel complex (14%) with the probable structure 60 is found (Eq. (17)) . With nickel peroxide in chloroform 30% 58 and 47% 60 are obtained... 

The greatest advantage is the electrocatalytic mode of oxidation. In chemical oxidations the reduced form of the oxidant is obtained as by-product. This needs a careful waste treatment to prevent pollutional problems or it has to be regenerated in an additional reaction. At the nickel hydroxide electrode, however, nickel oxide hydroxide is continuously reformed from the hydroxide, so that only electric current is used as reagent. This makes this oxidation also of interest for technical applications. 

Electrodes. A number of different types of nickel oxide electrodes have been used. The term nickel oxide is common usage for the active materials that are actually hydrated hydroxides at nickel oxidation state 2+, in the discharged condition, and nickel oxide hydroxide, NiO-OH, nickel oxidation state 3+, in the charged condition. Nickelous hydroxide, Ni(OH)i, can be precipitated from acidic solutions of bivalent nickel either by the addition of sodium hydroxide or by cathodic processes to cause an increase in the interfacial pH at the solution-electrode surface. See also Nickel. 

An alternative approach is precipitation by combining an alkaline NaAlC>2 solution with an acidic nickel nitrate solution [51]. In this case as well, hydrotalcite-like species are probably formed first although, due to the very high nickel contents reported, some nickel hydroxide forms as well. Pure hydrotalcite-like structure are reported to form for Ni Al atomic ratios between 2 and 3 [52] or 4 [53] outside this range the hydroxides of the excess species form as additional phases. Rapid precipitation tends to form pure Al(OH)3 due to the lower solubility. Aging can lead to recrystallization of some of the pure hydroxides to the hydrotalcite structure as well. 

The nickel ion forms two rather stable ammonia complexes. When a small amount of ammonium hydroxide solution is added to a solution of a nickel salt (green in color) a pale green precipitate of nickel hydroxide, Ni(OH), is formed. On addition of more ammonium hydroxide solution this dissolves to give a blue solution, which with still more ammonium hydroxide changes color to light blue-violet. 

The hydrated salts of nickel such as nickel sulfate, NiSO GHgO. and nickel chloride, NiCU GHsO, are green in color. Nickelous hy droxide, Ni(OH)2, formed as an apple-green precipitate by addition of alkali to a solution containing nickelous ion. When heated it pro duces the insoluble green substance nickelous oxide, NiO. Nickelous hydroxide is soluble in ammonium hydroxide, forming ammonia com plexes such as Ni(NH3)4(HoO). + + and Ni(NHg)g+ +. ... 

It was found that addition of hydroxide anion in dimethylformamide or dimethylsulfoxide to metal(II) corrole complexes results in the appearance of much sharper absorption bands relative to the starting compounds. These findings were considered consistent with the idea that an anionic, 18 Jt-electron aromatic corrole complex (e.g., 2.119) is formed as the result of what appears to be a formal deprotonation process (Scheme 2.1.25). That deprotonation actually occurs was inferred from acid-base titrations involving nickel(II) and copper(II) corroles. The conclusion that these species are anionic aromatic compounds came from an appreciation that their electronic spectra resemble those recorded for divalent metallo-porphyrins. In any event, the anion that results was found to be quenched upon acidification, regenerating the corresponding non-aromatic metallocorroles. ... 

Anodic oxidation of glucose gives mainly the glucono-(5-lactone (XCI) or gluconic acid (XCII) [Eq. (55)] [133-135]. Formation of aldonic acids from aldoses is the most commonly observed process in other cases [126]. Additional work has been done in the area of indirect anodic oxidation of partially protected carbohydrates at a nickel hydroxide anode [136]. 

Shohat and Mandler (37), and more recently Turyan et al. (33), have reported additional studies of patterning inorganic materials. The goal of the first report was to develop an approach for driving local acid-base reactions on surfaces. The motivation stems from previous work in which stable metal oxides, e.g., nickel hydroxide, served as an anchor for attaching organic and biological molecules onto surfaces in specific patterns. 

Methylpyridine from its oxide 164 Raney nickel (ca. 1 g) is added to a solution of the amine oxide (20 g) in glacial acetic acid (60 ml) and acetic anhydride (10 ml) and the mixture is shaken vigorously under hydrogen at room temperature. When hydrogen absorption ceases most of the nickel can be simply filtered off the filtrate is treated with concentrated hydrochloric acid (about 20 ml) and concentrated to a syrup at 80° under water-pump vacuum. Addition of dilute sodium hydroxide to the residue precipitates nickel hydroxide. After a short time the free base is distilled in steam, separated from the distillate by addition of sodium hydroxide, and dried for several days over solid sodium hydroxide. The residue of base in the aqueous phase is isolated by extraction with ether. Distillation of the united fractions of base affords pure 4-methylpyridine, b.p. 144-145°/760 mm (39.2 g, 84%). 

Orange-red crystals. The water of hydration is completely removed by heating to 100°C. Very soluble, even in cold water decomposed to Ni(CN)s by mineral acids. Forms black precipitates of higher nickel hydroxides on addition of hypobromites. 

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