H2 reduction

The Zn /Zn reduction potential is more negative than the H3 O /H2 reduction potential (-0.76 V vs. 0 V), so zinc is the anode in this cell. Zinc is oxidized and hydronium ions are reduced, causing electrons to flow from the more negative zinc electrode to the less negative SHE. Again, we reverse the direction of the half-reaction with the more negative potential and find E by subtracting the half-cell potentials ... 

Samples of high area powders and of supported metals may be applied to the CaF2 support plate by a spraying technique, previously described In detall(ll). In Figure 1, we show a half plate design In which a supported metal deposit, produced by H2 reduction of metal Ions held on the support, occupies one half of the plate while the pure support occupies the other half. 

Figure 3. Schematic representation of the selective synthesis of metal nanowires and nanoparticles by the Sintering Controlled Synthesis approach, (a) Mesoporous silica, (b) impregnation of mesoporous silica with metal ions, (c) addition of water/alcohol vapors and UV-irradiation, or wet H2-reduction, (d) formation of metal nanowires, (e) dry H2-reduction, (f) formation of metal nanoparticles.

It is known that Au nanoparticles efficiently catalyze various reactions, but its activity greatly depends on the degree of dispersion, support, and preparation method. We tried to synthesize Au wires and particles by our photo- and H2-reduction. For the S5mthesis of Au nanowires, several groups use HAUCI4 as a precursor. 

Significant advances have been made in this decade in electrochemical H2 separation, mostly through the use of solid polymer electrolytes. Since the overpotentials for H2 reduction and oxidation are extremely low at properly constructed gas diffusion electrodes, very high current densities are achievable at low total polarization. Sedlak [13] plated thin layer of Pt directly on Nafion proton conductors 0.1-0.2cm in thickness, and obtained nearly 1200 mA/cm2 at less than 0.3 V. The... 

H2S in the sweep gas, as shown by the open symbols. However, this fuel gas, containing 17.5% C02 and 17.5% H20, offers a strongly competitive reaction to H2S reduction, namely Eq. (35). Since the E° for this reaction is nearly equal to that for Eq. (30), it would be expected to occur to a much greater degree than (30). However, the oxidation reaction at the anode,... 

Figure 5.6 shows the XRD patterns of Ru/Al203 and Ru/Mn/Al203 after catalyst calcination, H2 reduction, and FT reaction. After catalyst calcination, the diffraction peaks assigned to Mn20310 were clearly observed in Ru/Mn/Al203,... 

Figure 5.7 shows the TEM image of Ru/Mn/Al203 catalyst after H2 reduction at 473 K. A lot of round-shaped particles that correspond to Ru metals can be observed on the catalyst surface. The average particle size (d) can be obtained using the equation... 

Hydrogen uptake of reduced catalysts (X) was measured by volumetric method with an AUTOSORB-l-C analyzer (Quantachrome Instruments). Hydrogen adsorption was carried out at 373 K after in situ H2 reduction at 773 K for 6 h in the adsorption cell. The dispersion and particle size of metallic Co were calculated by the following equations, assuming that the stoichiometry for hydrogen adsorption on the metallic site is unity ... 

In none of the cases discussed above is molecular hydrogen involved. The first report of the stoichiometric reduction of coordinated carbon monoxide by molecular hydrogen is that published by Bercaw et al. (35, 36). They reported that mononuclear carbonyl and hydride complexes of bis(pentamethylcyclopentadienyl)zirconium are capable of promoting stoichiometric H2 reduction of CO to methoxide under mild conditions. Thus, treatment of the dicarbonyl complex (rj5-C5Me5)2Zr(CO)2 with... 

The tert-butyl cluster Ni4(CNR)7 also catalyzed slowly the selective H2 reduction of the isocyanide to ferf-butylmethylamine (394). A problem arose in that the excess isocyanide resulted in formation of Ni(CNR)4, which is relatively inactive, but this was circumvented by using for the isocyanide source a buffered solution containing Ni4(CNR)7 and Ni(CNR)4 in a 1 10 ratio ... 

Of interest is the fact that the H2 required for the reduction of formyl to methoxide in reaction (73) is thought (428, 429) to come from a second zirconium moiety, ZrH2. The H2 reduction to coordinated hydroxymethyl in Eq. (72) could presumably go via a mononuclear H2M(CHO) intermediate, but such a reaction has not been demonstrated, nor has the final hydrogenolysis step via a presumed H2M(CH2OH) intermediate. Loss of water from this to give a carbene HM=CH2 (431, 432) followed by further reactions with H2 and CO, provides speculative pathways to higher hydrocarbons (417, 419a, 430, 433). 

---