Heterogene Katalysatoren – fundamental betrachtet

Abstract

Ein heterogener Katalysator ist ein Funktionsmaterial, das mit seinen Reaktanten unter Reaktionsbedingungen kontinuierlich aktive Zentren erzeugt. Diese Zentren verändern die Geschwindigkeit chemischer Reaktionen der an sie gebundenen Reaktanten, ohne die Lage des thermodynamischen Gleichgewichtes dieser Stoffe zu verändern.

Template-based synthesis of metallic Pd nanotubes by electroless deposition and their use as catalysts in the 4-nitrophenol model reaction

“…It is a significant parameter for evaluating the catalytic activity of a specific catalyst in heterogeneous catalysis. 49 The surface area of a catalyst is sometimes hardly calculable. The massnormalized rate constant (k M ) can also be taken as a characterisation parameter.…”

Kinetics of Lifetime Changes in Bimetallic Nanocatalysts Revealed by Quick X‐ray Absorption Spectroscopy

“…[9][10][11] Whilst catalysts were originally assumed to be static substances,intense research in the past decades has witnessed that (bi)metal catalysts are dynamically changing nanomaterials under reaction conditions. [12] During the catalyst lifetime, multiple atomic scale processes shape the working state of the catalyst and thereby influence its performance.I tg oes without saying that understanding these processes and detailing their kinetics is of crucial importance to control their occurrence and thus the catalyst performance.T ot his aim, techniques which provide high time resolution, but do not require long range order and can be applied in situ, are crucial for interrogating the kinetic behavior of (often disordered) bimetallic nanocatalysts under operating conditions.F or example,i ns itu, dispersive and quick X-ray absorption spectroscopy (XAS) have established ar ole of utmost importance in uncovering the motifs of (bi)metallic nanoparticle restructuring. [13][14][15][16][17][18] Herein, we probe the dynamic lifetime changes in aPt 13 In 9 model nanocatalyst induced by high-temperature O 2 -H 2 redox cycling with quick X-ray absorption spectroscopy (QXAS).…”

In Situ Growth and Characterization of Metal Oxide Nanoparticles within Polyelectrolyte Membranes

“…Doing so endears the composite material to applications in heterogeneous catalysis, [1][2][3] sensors [4] for both biological compounds [5] and chemical warfare agents; [6,7] actuators, [8] optoelectronics, [9,10] energy storage, [11] and chemical protection. The method is demonstrated drawing on the example of Nafion membranes and avariety of metal oxides with an emphasis placed on zinc oxide.T he in situ formation of nanoparticles is controlled by changing the solvent composition and conditions of synthesis that for the first time allows one to tailor not only the size, but also the nanoparticle shape,g iving ap reference to growth of ap articular crystal facet.…”

“…Doing so endears the composite material to applications in heterogeneous catalysis, [1][2][3] sensors [4] for both biological compounds [5] and chemical warfare agents; [6,7] actuators, [8] optoelectronics, [9,10] energy storage, [11] and chemical protection. Doing so endears the composite material to applications in heterogeneous catalysis, [1][2][3] sensors [4] for both biological compounds [5] and chemical warfare agents; [6,7] actuators, [8] optoelectronics, [9,10] energy storage, [11] and chemical protection.…”

“…The produced nanocomposite films are flexible,m echanically robust and have ap otential to be employed in sensing,o ptoelectronics and catalysis.There is atremendous demand in developing novel polymer composites that contain an inorganic phase with particular interest towards the inclusion of semiconducting metal oxide nanoparticles (MONP). Doing so endears the composite material to applications in heterogeneous catalysis, [1][2][3] sensors [4] for both biological compounds [5] and chemical warfare agents; [6,7] actuators, [8] optoelectronics, [9,10] energy storage, [11] and chemical protection. [12] In this study,w ef abricate MONP-polyelectrolyte nanocomposites and investigate the conditions that lead to the in situ growth of MONP within hydrated polyelectrolyte films impregnated by aqueous solutions of metal salts.B yi nvoking consecutive reaction schemes,the metal cations are converted to MONP within the polyelectrolyte matrix.…”