CO Oxidation at Near-Ambient Temperatures over TiO2-Supported Pd-Cu Catalysts: Promoting Effect of Pd-Cu Nanointerface and TiO2 Morphology

Palladium-modified TiO2 films in a photocatalytic microreactor: evaluation of radiation absorption properties and pollutant degradation efficiency

Pure (TiO₂) and 0.1 nominal atomic percent of palladium-modified TiO₂ (Pd-TiO₂) films were synthesized via a sol-gel method and compared through their physicochemical properties and photocatalytic activity in the degradation of an emerging contaminant, 17-α-ethinylestradiol (EE2). The activity of the films was studied using a continuous flow, planar microreactor under simulated sunlight. Catalysts characterization included X-ray diffraction, UV-Visible diffuse reflectance and transmittance spectroscopy, atomic force microscopy, transmission electron microscopy, Raman spectroscopy, N₂ physisorption analysis, and X-ray photoelectron spectroscopy. The modification of TiO₂ with palladium confined the size of anatase phase crystallites, increased the specific surface area and improved radiation absorption. PdO domains on TiO₂ were observed. In all the tested conditions, higher conversion of EE2 was achieved with the Pd-TiO₂ film compared with the TiO₂ film, presenting an 80% increase in the reaction rate. The performance of the catalytic films was also assessed by the calculation of two efficiency parameters: radiation absorption efficiency and quantum efficiency of reaction. The Pd-TiO₂ film showed a notable enhancement of the absorption of the incident radiation and a more efficient utilization of the absorbed photons to degrade the target pollutant.

Facile Microwave Synthesis of Hierarchical Porous Copper Oxide and Its Catalytic Activity and Kinetics for Carbon Monoxide Oxidation

The synthesis of copper oxide (CuO)-based nanomaterials has received a tremendous deal of interest in recent years. Particularly, the design and development of novel CuO structures with improved physical and chemical properties have attracted immense attention, especially for catalysis applications. We report on a rational, rapid, and surfactant-free microwave synthesis (MWS) of hierarchical porous copper oxide (HP-CuO) with a three-dimensional (3D) sponge-like topology using an MWS reactor. The activity of the microwave (MW)-synthesized HP-CuO catalysts for carbon monoxide (CO) oxidation was studied and compared to CuO prepared by the conventional heating method (CHM). Results showed that HP-CuO catalysts prepared by MWS for 10 and 30 min surpassed the CuO catalyst prepared by CHM, exhibiting T ₈₀ of 98 and 115 °C, respectively, as compared to 185 °C of CuO prepared by CHM (T₈₀ is the temperature corresponding to 80% CO conversion). In addition, the MW-synthesized HP-CuO catalysts outperformed the CHM-synthesized CuO, achieving a 100% CO conversion at 150 °C compared to 240 °C in the case of CuO prepared by CHM. Interestingly, the HP-CuO catalyst expressed workable CO conversion kinetics with a reaction rate of c.a.35 μmol s^-1 g^-1 at 150 °C and apparent activation energy (E _a) of 82 kJ mol^-1. The HP-CuO catalyst showed excellent cycling and long-term stabilities for CO oxidation up to 4 cycles and 72 h on the stream, respectively. The enhanced catalytic activity and stability of the HP-CuO catalyst appear to result from the unique topological and structural features of HP-CuO, which were revealed by SEM, XRD, Raman, BET, TGA, XPS, and TPR techniques.

Electrochemical Reduction of CO2: A Review of Cobalt Based Catalysts for Carbon Dioxide Conversion to Fuels

Electrochemical CO2 reduction reaction (CO2RR) provides a promising approach to curbing harmful emissions contributing to global warming. However, several challenges hinder the commercialization of this technology, including high overpotentials, electrode instability, and low Faradic efficiencies of desirable products. Several materials have been developed to overcome these challenges. This mini-review discusses the recent performance of various cobalt (Co) electrocatalysts, including Co-single atom, Co-multi metals, Co-complexes, Co-based metal-organic frameworks (MOFs), Co-based covalent organic frameworks (COFs), Co-nitrides, and Co-oxides. These materials are reviewed with respect to their stability of facilitating CO2 conversion to valuable products, and a summary of the current literature is highlighted, along with future perspectives for the development of efficient CO2RR.