Brpnsted-Evans-Polanyi relation

In the present chapter, we have attempted to illustrate how surface bonding and catalytic activity are closely related. One of the main conclusions is that adsorption energies of the main intermediates in a surface catalyzed reaction is often a very good descriptor of the catalytic activity. The underlying reason is that we find correlations, Brpnsted-Evans-Polanyi relations, between activation barriers and reaction energies for a number of surface reactions. When combined with simple kinetic models such correlations lead to volcano-shaped relationships between catalytic activity and adsorption energies. 

The large value of a in these Brpnsted-Evans-Polanyi relations is consistent with a late transition state for the dissociation reactions as discussed in Chapter 2. The only parameter in the universal relations is the reaction energy Er, which can be easily calculated. 

Reactant or product states of surface reactions are often (de-)stabilized by the presence of other adsorbates. This implies a change in the reaction energy as a function of overlayer composition. The Brpnsted-Evans-Polanyi relation again provides an elegant procedure to estimate the effect of lateral interactions on changes in the activation energies. 

Voj vodic A, Calle-Vallejo F, Guo W, Wang S, Toftelund A, Studt F, Shen J, Man IC, Rossmeisl J, Bligaard T, Nprskov JK, Abild-Pedersen F. On the behavior of Brpnsted-Evans-Polanyi relations for transition metal oxides. J Chem Phys 2011 134 244509. 

Wang SG, Temel B, Shen JA, Jones G, Grabow LC, Studt F, Bligaard T, Abild-Pedersen F, Christensen CH, Nprskov JK. Universal Brpnsted-Evans-Polanyi relations for C-C, C-O, C-N, N-O, N-N, and 0-0 dissociation reactions. Catal Lett 2011 141 370-373. 

BUgaard T, Nprskov JK, Dahl S, Matthiesen J, Christensen CH, Sehested J. The Brpnsted-Evans-Polanyi relation and the volcano curve in heterogeneous catalysis. J Catal 2004 224 206. 

The Brpnsted—Evans Polanyi Reaction-Rate Expression Relations... 

In this section, we move from the elucidation of molecular and atomic adsorption to the fundamental features that control smface reactivity. We start by initially describing dissociative adsorption processes. We focus on elucidating surface chemistry as well as the understanding of how the metal substrate influences the intrinsic surface reactivity. We will also pay attention to geometric ensemble-size related requirements. The Brpnsted-Evans Polanyi relationship between transition-state energy and reaction energy discussed in Chapter 2 is particularly useful in understanding differences in reactivity between different metal surfaces. 

One can then assume a Brpnsted-Evans-Polanyi relationship to relate the dependence of rate constant fc i to the overpotential E ... 

Owing to their strong bond on Ru(OOOl), mixed COa 0.55 V, the shift of the equilibrium between water and adsorbed OHad/Oad towards the latter increases the density of the respective species in the intermixed adlayer, which increases the repulsions between the adsorbed species and hence leads to more weakly bound OHad/Oad and COad species. These latter species are less stable against COOHad or CO2 formation, because of the reduced reaction barrier ( Brpnsted-Polanyi-Evans relation [Bronstedt, 1928]), and can support a reaction via (14.9) or (14.12), respectively, at low rates. (Note that the total density of the adlayer does not need to remain constant, although also this is possible.)... 

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