Magdalena Diak

Noble metal-based bimetallic nanoparticles: the effect of the structure on the optical, catalytic and photocatalytic properties

Nanoparticles composed of two different metal elements show novel electronic, optical, catalytic or photocatalytic properties from monometallic nanoparticles. Bimetallic nanoparticles could show not only the combination of the properties related to the presence of two individual metals, but also new properties due to a synergy between two metals. The structure of bimetallic nanoparticles can be oriented in random alloy, alloy with an intermetallic compound, cluster-in-cluster or core-shell structures and is strictly dependent on the relative strengths of metal-metal bond, surface energies of bulk elements, relative atomic sizes, preparation method and conditions, etc. In this review, selected properties, such as structure, optical, catalytic and photocatalytic of noble metals-based bimetallic nanoparticles, are discussed together with preparation routes. The effects of preparation method conditions as well as metal properties on the final structure of bimetallic nanoparticles (from alloy to core-shell structure) are followed. The role of bimetallic nanoparticles in heterogeneous catalysis and photocatalysis are discussed. Furthermore, structure and optical characteristics of bimetallic nanoparticles are described in relation to the some features of monometallic NPs. Such a complex approach allows to systematize knowledge and to identify the future direction of research.

Photocatalytic ozonation using doped TiO2 catalysts for the removal of parabens in water

Conventional wastewater treatments are inefficient for the removal of parabens. The aim of this study was finding a suitable solution using ozone and UVA irradiation combined with TiO2 catalysts doped with different noble metals (Ag, Pt, Pd, Au). Photocatalytic ozonation required lower amounts of ozone for higher efficiency on the removal of parabens, chemical oxygen demand (COD) and total organic carbon (TOC). The best catalyst for the initial contaminants degradation was 0.5% Ag-TiO2 leading to total parabens removal using 46mgO3/L. Due to the relative low mineralization achieved, the toxicity of the treated solutions was still compared with the initial one over several species (Vibrio fischeri, Lepidium sativum and Corbicula fluminea). All the treatments applied led to a clear decrease on the toxicity compared with initial mixture of parabens. From an economical point of view, it was concluded that the presence of UVA irradiation increased the energy consumption compared with catalytic ozonation with these catalysts but it can decrease the time of reaction. From the by-products analysis, it was concluded that hydroxylation appears to be the most significant reaction pathway and the main responsible for parabens degradation.

The Photocatalytic Conversion of (Biodiesel Derived) Glycerol to Hydrogen - A Short Review and Preliminary Experimental Results Part 1: A Review

Abstract The paper presents a short review of published results about different methods of waste glycerol conversion to the various chemicals and energy carriers as well the preliminary experimental results of the photocatalytic glycerol conversion into hydrogen. The first part of the paper presents literature data pertaining to the glycerol utilization, including thermal methods (incineration, pyrolysis, gasification and reforming), catalytic oxidation, chemical and biochemical conversion and photoconversion into hydrogen, are presented. The mechanism of selected processes and reaction conditions are also discussed. The second part of the paper presents the results of the hydrogen production over irradiated aqueous glycerol solution containing TiO2-based photocatalysts (TiO2- modified W, Mn, Cr, Ni, Co, Pt, Pd, Au and Ag). The test runs were performed in the batch and semi-batch reactors equipped with Xe lamps as a light source. Much higher hydrogen productivity was observed for the titania modified by noble metals than for transition metal used for modification. The highest hydrogen productivity (24.2 mmol H2·gcat-1·h-1) was reached in the presence of Pt/TiO2, when glycerol concentration in the solution equaled to 4.5 wt.% and the photocatalysts loading in the suspension was ~ 0.042 wt.%.

The Photocatalytic Conversion of (Biodiesel Derived) Glycerol to Hydrogen - A Short Review and Preliminary Experimental Results Part 2: Photocatalytic Conversion of Glycerol to Hydrogen in Batch and Semi-batch Laboratory Reactors

Abstract The paper presents a short review of published results about different methods of waste glycerol conversion to the various chemicals and energy carriers as well the preliminary experimental results of the photocatalytic glycerol conversion into hydrogen. The first part of the paper presents literature data pertaining to the glycerol utilization, including thermal methods (incineration, pyrolysis, gasification and reforming), catalytic oxidation, chemical and biochemical conversion and photoconversion into hydrogen, are presented. The mechanism of selected processes and reaction conditions are also discussed. The second part of the paper presents the results of the hydrogen production over irradiated aqueous glycerol solution containing TiO2-based photocatalysts (TiO2-modified W, Mn, Cr, Ni, Co, Pt, Pd, Au and Ag). The test runs were performed in the batch and semi-batch reactors equipped with Xe lamps as a light source. Much higher hydrogen productivity was observed for the titania modified by noble metals than for transition metal used for modification. The highest hydrogen productivity (24.2 mmol H2·gcat-1·h-1) was reached in the presence of Pt/TiO2, when glycerol concentration in the solution equaled to 4.5 wt.% and the photocatalysts loading in the suspension was ~ 0.042 wt.%.