Functional surfaces in heterogeneous catalysis: A short review

Abstract

A Heterogeneous catalysis and functional surfaces are intimately connected. Surface functionalities mediate the catalytic reactions. However, the surface must fulfil several requirements: adsorption of the reactants on the surface must be energetically favoured (but reversible), the surface functionalities must enhance the dissociation of chemical bonds in the reactant and the formation of new ones which will lead to the reaction's product(s), and finally the product(s) must be able to desorb and leave the surface. It was shown that for the ammonia synthesis on ruthenium single crystalline surfaces, both the geometric and electronic functionalities of step edges are crucial to dissociate nitrogen. Another wellinvestigated reaction is the catalytic oxidation of carbon monoxide over platinum and oxidized ruthenium. For both metals, the surface is dynamic, which leads to a change in its functionalities during reaction. These few examples of simple reactions already show the complexity of the necessary surface functionalities for heterogeneous catalysis and the problems connected with the understanding of rather simple reaction mechanisms. The key objective in catalysis research consists in tailoring the geometric and electronic properties of catalysts depending on the target reactions. One attempt in this direction is the investigation of binary alloys and, more recently, of intermetallic compounds. Here the adsorption properties of the reactants could be drastically changed. A completely different way of changing adsorption properties also exists for semiconductor surfaces: the direct application of electric fields leads to a change of charge carriers near the surface -the electro-adsorptive effect.

Heterogeneous Catalysis

“…It may be speculated whether other forms of energy supply to a catalytic system, such as photoactivation,240 the generation of electric fields in electrocatalysis159b, 241 or the stimulation from radicals in plasma catalysis,242 can also lead to such active centers directly or with a low additional energy input. Much more often the effect on the molecular structure of the reactants243 by nonthermal energy, induced directly or through the catalyst, is investigated as a central catalyst function.…”

Postfunctionalization of Azido or Alkyne Poly(3,4‐ethylenedioxythiophene) Surfaces: Superhydrophobic and Parahydrophobic Surfaces

“…Propargyloxymethyl-EDOT : Yield 59%; slightly yellow solid; 1 1 g of (4-hydroxybutyl)-EDOT (4.7 mmol) was dissolved in dry THF (20 mL). 125 mg of sodium hydride (5.2 mmol, 1.1 eq) was added at 0 °C.…”

“…The functionality can be used to manipulate very diverse behaviors such as optical, biological, physical, or chemical properties. [ 1,2 ] Among the functional surfaces, hydrophobic and superhydrophobic ones are of particular interest. [3][4][5][6] Their wide range of applications (from selfcleaning glasses to antibioadhesion surfaces passing through waterproof textile) make them a real challenge for the scientifi c and industrial communities.…”

Time- and Temperature-Varying Activation Energies: Isobutane Selective Oxidation to Methacrolein over Phosphomolybdic Acid and Copper(II) Phosphomolybdates

“…The plots in Figures 4-7 show some oscillatory behavior [15,16], as sometimes observed in heterogeneous catalytic oxidation product reactions [17]. This is likely to be a consequence of heat and mass transport effects [15], as well as activation and deactivation of active sites [18].…”