Nickel alloys molybdate

Furthermore, [NiCit] can readily be reduced to metallic nickel (c.f. Eq. 39) at the potential where the Ni-Mo alloy is formed. Yet, no such reduction is shown in Eqs. (42) and (43), in which Mo is first reduced from the hexavalent molybdate to the tetrava-lent molybdenum dioxide, and then further to metallic molybdenum. A solution, in which the concentrations of Ni and Cit - were equal, was used and it was assumed that all citrate ions were bound to Ni in [NiCit] . This assumption ignores the possible existence of complexes of the type [(Mo04)(Cit)(H)ni] (written for short as [l,l,m] where m is the number of protons in the complex), in spite of the fact that such complexes are well known (cf.. Fig. 13a). In addition, detailed calculation of the distribution of species in a NP and Cit - mixture shows that, when the ratio of the concentrations of the two ions is unity, there are still a few percents of free Ni and Cif" ions not bound in the complex, as seen if Fig. lb. 

A 25 nm-thick layer with a Ni/Mo atomic ratio of 4 1 was indeed detected by AES and EDS. The mixed Ni-Mo oxide is claimed to catalyze the HER. Next, when the polarization is increased, the mixed oxide is further reduced to a surface compound that inhibits the HER and is more catalytic for reduction of molybdate and nickel ions, fonning an alloy according to the reaction ... 

As Stated earlier the most probable mechanism for Ni and Mo codeposition is the one reported by Podlaha and Landolt [117-120] after X-ray fluorescence analysis of the electrodeposited alloy. Their investigations were performed under controlled mass transport conditions (rotating cylinder electrode). The model assumes that the Ni electrodeposition occurs on the surface not covered by the molybdate ions as a reaction intermediate, by direct reduction of nickel species (all of them being complex of Ni " cations with the citrate anions), independently on the molybdate reaction which can occur only in the presence of nickel species [117-120], The model of the Mo-Ni alloy electrodeposition is described by the following reduction reactions ... 

Seawater and salt solutions. Titanium alloys exhibit excellent resistance to most salt solutions over a wide range of pH and temperatures, (jood performance can be expected in sulfates, sulfites, borates, phosphates, cyanides, carbonates, and bicarbonates. Similar results can be expected with oxidizing anionic salts such as nitrates, molybdates, chromates, permanganates, and vanadates and also with oxidizing cationic salts including ferric, cupric, and nickel compounds. 

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