Coprecipitation

Abstract: Novel gold catalysts were prepared by coprecipitation from an aqueous solution of HAuCl4 and the nitrates of various transition metals. Calcination of the coprecipitates in air at 400 °C produced ultrafine gold particles smaller than 10 nm which were uniformly dispersed on the transition metal oxides. Among them, Auα-Fe2O3, AuCo3O4, and AuNiO were highly active for H2 and CO oxidation, showing markedly enhanced catalytic activities due to the combined effect of gold and the transition metal oxides. For the oxidation of CO they were active even at a temperature as low as −70 °C.

Abstract: A variety of gold catalysts can be used to catalyze the oxidation of carbon monoxide at temperatures as low as −70 °C and are stable in a moistened gas atmosphere. The novel catalysts, prepared by coprecipitation, are composed of ultra-fine gold particles and one of the oxides of 3d transition metals of group VIII, namely, Fe, Co, and Ni.

Abstract: In this study we report the effects of the Ni content on the electrochemical properties and the structural and thermal stabilities of Li[Ni x Co y Mn z ]O 2 ( x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) synthesized via a coprecipitation method. The electrochemical and thermal properties of Li[Ni x Co y Mn z ]O 2 are strongly dependent on its composition. An increase of the Ni content results in an increase of specific discharge capacity and total residual lithium content but the corresponding capacity retention and safety characteristics gradually decreased. The structural stability is related to the thermal and electrochemical stabilities, as confirmed by X-ray diffraction, thermal gravimetric analysis, and differential scanning calorimetry. Developing an ideal cathode material with both high capacity and safety will be a challenging task that requires precise control of microstructure and physico-chemical properties of the electrode.

Abstract: Cost-effective production of solar fuels requires robust and earth-abundant oxygen evolution reaction (OER) catalysts. Herein, we report that ultrathin nanoplates of cobalt–manganese layered double hydroxide (CoMn LDH) are a highly active and stable oxygen evolution catalyst. The catalyst was fabricated by a one-pot coprecipitation method at room temperature, and its turnover frequency (TOF) is more than 20 times higher than the TOFs of Co and Mn oxides and hydroxides, and 9 times higher than the TOF of a precious IrO2 catalyst. The activity of the catalyst was promoted by anodic conditioning, which was proposed to form amorphous regions and reactive Co(IV) species on the surface. The stability of the catalyst was demonstrated by continued electrolysis.

Abstract: α-MnO2 was synthesized by a very simple coprecipitation technique and tested as active electrode material for an electrochemical supercapacitor. The powder presents a poorly crystallized cryptomelane phase with a chemical composition of K0.05MnO2H0.10·0.15H2O. Different aqueous electrolytes were tested including 0.1 M Na2SO4, 0.5 M K2HPO4/KH2PO4 buffer solution, 0.3 M H2SO4, and 1 M NaOH, but interesting pseudocapacitance behavior was only observed in the case of 0.1 M Na2SO4. Further testing using this electrolyte showed that an average capacitance of 166 F/g can be reproducibly obtained within a voltage range −0.4/+0.5 V vs Hg/Hg2SO4 using a sweep rate of 2 mV/s. This interesting value is mainly due to the chimisorption of Na+ ions and/or protons at the surface of the α-MnO2 electrode. Nearly all the Mn surface atoms are involved in the pseudocapacitive process. Therefore, the high specific capacitance seems to be related to the high surface area of the MnO2 powder rather than intercalation of Na+ ions ...