Electrodeposited Copper Nanocatalysts for CO2 Electroreduction: Effect of Electrodeposition Conditions on Catalysts’ Morphology and Selectivity

Catalytic electroreduction of carbon dioxide represents a promising technology both to reduce CO2 emissions and to store electrical energy from discontinuous sources. In this work, electrochemical deposition of copper on to a gas-diffusion support was tested as a scalable and versatile nanosynthesis technique for the production of catalytic electrodes for CO2 electroreduction. The effect of deposition current density and additives (DAT, DTAB, PEG) on the catalysts’ structure was evaluated. The selectivity of the synthesized catalysts towards the production of CO was evaluated by analyzing the gaseous products obtained using the catalysts as cathodes in electroreduction tests. Catalyst morphology was deeply influenced by the deposition additives. Copper nanospheres, hemispherical microaggregates of nanowires, and shapeless structures were electrodeposited in the presence of dodecyltrimethylammonium bromide (DTAB), 3,5-diamino-1,2,4-triazole (DAT) and polyethylene glycol (PEG), respectively. The effect of the deposition current density on catalyst morphology was also observed and it was found to be additive-specific. DTAB nanostructured electrodes showed the highest selectivity towards CO production, probably attributable to a higher specific surface area. EDX and XPS analysis disclosed the presence of residual DAT and DTAB uniformly distributed onto the catalysts structure. No significant effects of electrodeposition current density and Cu(I)/Cu(II) ratio on the selectivity towards CO were found. In particular, DTAB and DAT electrodes yielded comparable selectivity, although they were characterized by the highest and lowest Cu(I)/Cu(II) ratio, respectively.

High Temperature Pyrolysis of Municipal Plastic Waste Using Me/Ni/ZSM-5 Catalysts: The Effect of Metal/Nickel Ratio

This work is dedicated to the high temperature pyrolysis of municipal plastic waste using Me/Ni/ZSM-5 catalysts. Catalysts were synthetized by wet impregnation. In addition to nickel, synthetic zeolite catalysts contain calcium, ceria, lanthanum, magnesia or manganese. Catalysts were prepared and tested using 0.1, 0.5 and 2.0 Me/Ni ratios. Catalyst morphology was investigated by SEM and surface analysis. Higher concentrations of second metals can block catalyst pore channels due to the more coke formation, which leads to smaller surface area. Furthermore, the chemicals used for the impregnation were among the catalyst grains, especially in case of 2.0 Me/Ni ratios. For pyrolysis, a horizontal tubular furnace reactor was used at 700 °C. The highest hydrogen and syngas yields were observed using ceria- and lanthanum-covered catalysts. The maximum production of syngas and hydrogen (69.8 and 49.2 mmol/g raw material) was found in the presence of Ce/Ni/ZSM-5 catalyst with a 0.5 Me/Ni ratio.

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Surface chemistry and pore topology affect mesitylene selectivity in acid-catalysed acetone condensation. Hydrogen improves both catalyst stability and condensation selectivity.

Looking for the “Dream Catalyst” for Hydrogen Peroxide Production from Hydrogen and Oxygen

The reaction between hydrogen and oxygen is in principle the simplest method to form hydrogen peroxide, but it is still a “dream process”, thus needing a “dream catalyst”. The aim of this review is to analyze critically the different heterogeneous catalysts used for the direct synthesis of H2O2 trying to determine the features that the ideal or “dream catalyst” should possess. This analysis will refer specifically to the following points: (i) the choice of the metal; (ii) the metal promoters used to improve the activity and/or the selectivity; (iii) the role of different supports and their acidic properties; (iv) the addition of halide promoters to inhibit undesired side reactions; (v) the addition of other promoters; (vi) the effects of particle morphology; and (vii) the effects of different synthetic methods on catalyst morphology and performance.