Improving manganese oxides as cathodic catalysts in direct methanol/hydrogen peroxide fuel cells by incorporation of Cu and Fe to promote oxygen reduction (OR) and hydrogen peroxide reduction (HPR) is reported. The Cu‐incorporated and Fe‐incorporated MnxOy were prepared by impregnation and solvothermal processes. From XRD, XPS, and XAS analyses, the obtained MnxOy consisted of MnO2 and mixed phases of Mn3O4 and Mn2O3 from impregnation and solvothermal methods, respectively. The Cu‐incorporated and Fe‐incorporated MnxOy included CuO and Fe2O3, respectively, through both methods. Addition of Cu and Fe decreased the BET surface area and increased the pore sizes as compared to the pristine MnO2. With the Fe : Mn molar ratio of 0.20 : 1, the Fe‐incorporated MnxOy from the solvothermal method presented the highest cathodic peaks under the cyclic voltammogram of HPR and OR at around 0.59 V of 11.59 mA cm−2 and −0.59 V of −12.33 mA cm−2, respectively. Compared to the Cu‐incorporated ones, the highest HPR peak at 0.68 V of 9.20 mA cm−2 and the highest OR peak at −0.59 V of −6.99 mA cm−2 were obtained from the Cu‐incorporated MnxOy prepared through the solvothermal method at the Cu : Mn molar ratio of 0.15 : 1. Incorporating Cu or Fe into MnO2 brought the improvement of electrocatalytic activity for HPR and OR. The Cu‐incorporated and Fe‐incorporated MnxOy from both methods showed a higher power density of μ‐DMFC than the pristine MnO2.
Co-promoted Cu/ZnO catalysts were studied for Fischer-Tropsch synthesis (FTS). All catalysts were prepared by the co-precipitation method, having the mass ratio of Co:Cu:Zn=0 (unpromoted), 0.05, 0.5:1:1, and characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). From XRD and XAS, the results confirmed the phase transformation of CuO to Cu foil and Co3O4 to Co foil in Co-promoted catalysts after reduction. After FTS reaction testing, the Co-promoted catalysts showed the decrease in methanol selectivity of 15 and 1.6% for 0.05Co-Cu/ZnO and 0.5Co-Cu/ZnO, respectively, and the increase in C5-C15 selectivity during 30 h of reaction.
Cu/ZnO catalysts were studied to enhance the methanol selectivity in Fischer-Tropsch synthesis (FTS). By knowing that the methanol production from syngas (CO/H2) accelerated the crystallization of Cu and ZnO and led to the deactivation of the catalysts, a small amount of iron added to the catalyst could improve the catalyst stability by suppressing the crystallization of Cu and ZnO. The promotional effects of iron on the textural properties, reduction behavior, and structural changes of the Cu-based FTS catalysts were investigated by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Their catalytic activity was measured at 10 bar and 190°C with H2/CO ratio of 2 and the FTS products were analyzed by GC. The product distribution was presented in terms of methanol, C1, C2-C4, and C5+ selectivity.
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