Understanding the mechanism of CO2 reduction on iron is crucial for the design of more efficient and cheaper iron electrocatalyst for CO2 conversion. In the present study, we have employed spin-polarized density functional theory calculations within the generalized gradient approximation (DFT-GGA) to elucidate the mechanism of CO2 reduction into carbon monoxide and formic acid on the Fe (100) facet. We also sort to understand the transformations of the other isomers of adsorbed CO2 on iron as earlier mechanistic studies are centred on the transformations of the C2v geometry alone and not the other possible conformations i.e., flip-C2v and Cs modes. Two alternative reduction routes were considered i.e., the direct CO2 dissociation against the hydrogen-assisted CO2 transformation through formate and carboxylate into CO and formic acid. Our results show that CO2 in the C2v mode is the precursor to the formation of both products i.e., CO and formic acid. Both the formation and transformation of CO2 in the Cs and flip-C2v is challenging kinetically and thermodynamically compared to the C2v mode. The formic acid formation is favoured over CO via the reverse water gas shift reaction mechanism on Fe (100). Both formic acid formation and CO formation will proceed via the carboxylate intermediate since formate is a stable intermediate whose transformation into formic acid is challenging both kinetically and thermodynamically. Graphic abstract

The inefficient collection of solid wastes is a global phenomenon that has received attention in recent years for the ever-increasing annual waste generation records. However, indicators to the effective application of the amassing routs are missing. Hence, the generally accepted source-sorting model was explored to identify the determinants that will enhance source separation of wastes at the workplace. This paper presents a foremost report on the indicators to an effective operation of solid wastes source segregation. A quantitatively examined data was collected in sixty-six working days during a monitoring and evaluation process of twenty sets of twin-dustbins that were located at the study area. The generated solid wastes were commonly sorted (65%) in comparison with the mixed collection. Most of the wastes were separated on the third month (80%) of education compared to the first (54%) and second months (61%). Wednesday displayed the working day with the utmost sorted wastes (73%) compared to the other days. All dustbins recorded impressive sorting at the different locations in the Institute. A little over one thousand Ghana cedis savings was made in the first year. Tested null hypothesis showed that, duration and timing of continuous education were significant determinants of the efficient source segregation, relative to the dustbin locations. Therefore, the daily education of waste generators on how to separate wastes at source and the economic benefits will enhance source separation irrespective of the location.

Polystyrene is an aromatic hydrocarbon plastic material with applications in the packaging, food, and construction industries. As a packaging material, it protects items against shocks and acts as an insulator in the construction of buildings and food preservation. The polystyrene bowl for food packaging has become a convention in the food and pastries industry in Ghana due to its clean, lightweight, and insulation properties. However, the corresponding waste litters its environment, chocks gutters, and does not decompose. For this reason, we explored the hot melt recycling technique to convert the PS wastes into valuable plastic plates that finds application in the artifact and souvenir industry. The incorporation of a 20% v/w lauric fatty acid (LFA) into the material matrix blocked micro holes in the finished product and induced a smooth surface. Characterizations included experiments such as Fourier Transform-Infra Red spectroscopy, melting point determination, tensile testing, and scanning electron microscopy (SEM). Generated data displayed the absence of a chemical bond between the PS molecules and the LFA additive. However, the methyl chains of the PS molecules were miscible with the saturated dodecyl chains of the LFA additive. Hence, the LFA additive was held in place by weak intermolecular forces between its chains and that of the PS molecules. The measured melting point of the recycled plastic with LFA content (rPS20) fell between 84-142 °C. Mechanically, the tensile strength dropped with the addition of LFA. The LFA induced a smooth surface morphology finishing in rPS20.

The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped LaMnO3 (LBM25) have been studied at the density functional theory (DFT) with Hubbard correction and the results compared with adsorption on 25% Ca-doped LaMnO3 (LCM25) and Sr-doped LaMnO3 (LSM25). The trend in the reduction energies at the Mn cation sites are predicted to be in the order LSM25 < LBM25 < LCM25. In addition, the trend in dissociation energies for the most exothermic dissociated precursors follow the order LBM25 < LSM25 < LCM25. The adsorption energies (− 2.14 to − 2.41 eV) calculated for the molecular O2 precursors at the Mn cation sites of LCM25, LSM25 and LBM25 are thermodynamically stable, when compared directly with the adsorption energies (Eads = − 0.56 to − 1.67 eV) reported for the stable molecular O2 precursors on the Pt, Ni, Pd, Cu and Ir {111} surfaces. The predicted Gibbs energies as a function of temperature (T = 500–1100 °C) and pressures (p = 0.2 atm) for the adsorption and dissociation on the surfaces were negative, an indication of the feasibility of oxygen reduction reaction on the {100} and {110} surfaces at typical operating temperatures reported in this work.