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Homogeneity and heterogeneity; only ' b ' is homogeneous Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image.A homogeneous feature is uniform in composition or character (i.e. color, shape, size, weight, height, distribution, texture, language, income, disease, temperature, radioactivity, architectural design, etc.); one that is heterogeneous ...
An electrocatalyst can be heterogeneous such as a platinized electrode. [1] Homogeneous electrocatalysts, which are soluble, assist in transferring electrons between the electrode and reactants, and/or facilitate an intermediate chemical transformation described by an overall half reaction. [2] Major challenges in electrocatalysts focus on fuel ...
Heterogeneous photocatalysis is a discipline which includes a large variety of reactions: mild or total oxidations, dehydrogenation, hydrogen transfer, 18 O 2 – 16 O 2 and deuterium-alkane isotopic exchange, metal deposition, water detoxification, and gaseous pollutant removal.
Biocatalysts can be thought of as an intermediate between homogeneous and heterogeneous catalysts, although strictly speaking soluble enzymes are homogeneous catalysts and membrane-bound enzymes are heterogeneous. Several factors affect the activity of enzymes (and other catalysts) including temperature, pH, the concentration of enzymes ...
Heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reagents or products. [1] The process contrasts with homogeneous catalysis where the reagents, products and catalyst exist in the same phase.
The separation of homogeneous catalysts from products can be challenging. In some cases involving high activity catalysts, the catalyst is not removed from the product. In other cases, distillation can extract volatile organic products. Homogeneous catalysts have limited thermal stability compared to heterogeneous catalysts.
The activity of heterogeneous catalysts in cross-coupling seems to be tied to the ability of the electrophile (usually an aryl halide) to undergo oxidative addition with an atom of Pd(0), whether on the solid catalyst surface or already in solution, after which the rest of the catalytic cycle will take place – in solution. Figure 1.
A homogeneous WOC [Co(Py 5)(H 2 O)](ClO 4) 2 [10] operates by a proton-coupled electron transfer to form a [Co III--OH] 2+ species, which on further oxidation forms a Co IV intermediate. The intermediate formed reacts with water to liberate O 2. The cobalt-polyoxometalate complex [Co 4 (H 2 O) 2 (α-PW 9 O 34) 2] 10− is highly efficient WOC. [11]