Cobalt Oxide on a Nanoporous TUD-1 Catalyst for Methylene Blue Dye Interaction DFT Studies and Degradation

Fenton and Fenton-like advanced oxidation processes (AOP) have been substantially utilized in wastewater treatment for the removal of organic contaminants. The present investigation explores the catalytic activity of cobalt dispersed over nanoporous silicate material (CoO/TUD-1), TUD-1, for the Fenton-type degradation of methylene blue (MB) dye present in wastewater, with hydrogen peroxide (H2O2) as an oxidant. The catalyst, which was prepared using the hydrothermal method, was characterized using analytical and spectroscopic techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption isotherms, UV-visible diffuse reflectance (DR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR). The results indicated that the CoO/TUD-1 possessed three-dimensional structures with a high surface area and a pore diameter capable of the uniform dispersion of cobalt species. Density functional theory (DFT) simulations were performed to study the most stable tetra coordinate adsorption configuration of a single Co atom on amorphous SiO2. To understand the geometric and electronic structure of this configuration, electron density differences, Bader charge, and partial density of states were examined. The results obtained from the DFT calculations confirmed the occurrence of electron transfer from the Co atom to the amorphous SiO2. The calculated adsorption energy was found to be −1.58 eV, which indicated that the MB dye was strongly adsorbed by parallel configuration mode and degraded more easily. Further, the addition of a 0.1g/L dose of the prepared CoO /TUD degraded the MB dye effectively (~95%) within 240 min of contact. Thus, CoO/TUD-1 is a potential material for the removal of organic contaminants and the degradation of dyes in wastewater treatment.

A hierarchical flower-like hollow alumina supported bimetallic AuPd nanoparticle catalyst for enhanced solvent-free ethylbenzene oxidation

Currently, oxidation of alkylaromatics is considered as one of the most crucial chemical technologies to produce high added-value alcohols, ketones and carboxylic acids, due to its significant importance both in fine synthetic chemistry and in the academic field. In this work, a novel hierarchical marigold-like hollow alumina supported bimetallic AuPd nanoparticle catalyst was successfully fabricated and employed for highly efficient solvent-free ethylbenzene oxidation to produce acetophenone with the coexistence of both molecular oxygen and tert-butyl hydroperoxide as the oxidant and the initiator. The as-fabricated bimetallic AuPd nanocatalyst conferred a superior catalytic performance to the corresponding monometallic counterparts and commercial Al2O3 or solid Al2O3 microsphere supported AuPd ones, along with a high acetophenone selectivity of 88.2% at a conversion of 50.9% under mild reaction conditions (120 °C and oxygen pressure of 1.0 MPa), as well as an unprecedentedly high turnover frequency value of 46 768 h-1. Such exceptional efficiency of the catalyst was related to both the significant synergy between the Au-Pd atoms and strong metal-support interactions, and the unique hierarchical micro/nanostructure of the support being beneficial to the close contact of reactants with surface adsorption and reaction sites and easy product diffusion. Moreover, the present bimetallic AuPd catalyst was recyclable and stable. The developed approach is expected to offer exciting opportunities for designing other supported monometallic or bimetallic catalysts with various active components applied in heterogeneous catalysis.