Ioannis Yentekakis

Abstract:

Mixed oxide materials with high lattice oxygen ion lability, typically ionically (O^2-)-conducting materials, can be used as catalyst supports and tunable metal-support interaction carriers, effectively controlling catalytic properties of the metal particles interfaced with them. This occurs via an effective dipolar layer of ionic promoter species formed at the catalyst particle surfaces, which imposes significant alterations on the adsorption properties of the reactants and reaction intermediates with concomitant dramatic effects on surface catalysis phenomena (catalytic performance) as discovered by Vayenas and his co-workers about three decades ago [1, 2]. The dipolar layer and its intensity (promoter species population) can be controlled electrochemically; the so-called Electrochemical Promotion of Catalysis (EPOC) or NEMCA effect [1, 2] can be spontaneously created on traditional-type highly dispersed catalysts via thermally-driven spillover of ionic species from the support on the nanoparticle surfaces [3, 4].
Remarkable achievements on energy and environmentally important catalytic reactions have been accomplished by this concept of promotion.
An additional innovative effect of the spontaneously created effective-double-layer on metal nano-particles, supported by high oxygen ion lability, has been recently discovered [5-6]. This concerns their stabilization against thermal sintering: a topic of great importance in industrial heterogeneous catalytic processes. A novel interpretative model for the action of the effective-double-layer on the two main mechanisms of particles growth, i.e. large particles’ migration and coalescence (PMC) and Ostwald ripening (OR), and thus on their sinter resistance behavior, was developed and discussed in the present paper together with some experimental results.

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[5] I.V. Yentekakis, G. Goula, P. Panagiotopoulou, S. Kampouri, M.J. Taylor, G. Kyriakou, R.M. Lambert, Appl. Catal. B 192 (2016) 357-364.
[6] I.V. Yentekakis, G. Goula, S. Kampouri, I. Betsi-Argyropoulou, P. Panagiotopoulou, M.J. Taylor, G. Kyriakou, R.M. Lambert, Catal. Lett. 148 (2018) 341-347.