Generalized Brønsted–Evans–Polanyi relationships and descriptors for O–H bond cleavage of organic molecules on transition metal surfaces

Linear Scaling Relationships for Furan Hydrodeoxygenation over Transition Metal and Bimetallic Surfaces

Brønsted-Evans-Polanyi (BEP) and transition-state-scaling (TSS) relationships have become valuable tools for the rational design of catalysts for complex reactions like hydrodeoxygenation (HDO) of bio-oil (containing heterocyclic and homocyclic molecules). In this work, BEP and TSS relationships are developed for all the elementary steps of furan activation (C and O hydrogenation and CHx -OHy scission, for both ring and open-ring intermediates) to oxygenates, ring-saturated compounds and deoxygenated products on the most stable facets of Ni, Co, Rh, Ru, Pt, Pd, Fe and Ir surfaces using Density Functional Theory (DFT) calculations. Furan ring opening barriers were found to be facile and strongly dependent on carbon and oxygen binding strength on the investigated surfaces. Our calculations suggest linear chain oxygenates form on Ir, Pt, Pd and Rh surfaces due to their low hydrogenation and high CHx -OHy scission barriers, while deoxygenated linear products are favoured on Fe and Ni surfaces due to their low CHx -OHy scission and moderate hydrogenation barriers. Bimetallic alloy catalysts were also screened for their potential HDO activity and PtFe catalysts were found to significantly lower the ring opening and deoxygenation barriers relative to the corresponding pure metals. The developed BEPs for monometallic surfaces can be extended to estimate the barriers on bimetallic surfaces for ring opening and ring hydrogenation reactions but fails to predict the barriers for open-ring activation reactions due to the change in transition state binding sites on the bimetallic surface. The obtained BEP and TSS relationships can be used to develop microkinetic models for facilitating accelerated catalyst discovery for HDO.

Single-atom alloy catalysts designed by first-principles calculations and artificial intelligence

Single-atom-alloy catalysts (SAACs) have recently become a frontier in catalysis research. Simultaneous optimization of reactants' facile dissociation and a balanced strength of intermediates' binding make them highly efficient catalysts for several industrially important reactions. However, discovery of new SAACs is hindered by lack of fast yet reliable prediction of catalytic properties of the large number of candidates. We address this problem by applying a compressed-sensing data-analytics approach parameterized with density-functional inputs. Besides consistently predicting efficiency of the experimentally studied SAACs, we identify more than 200 yet unreported promising candidates. Some of these candidates are more stable and efficient than the reported ones. We have also introduced a novel approach to a qualitative analysis of complex symbolic regression models based on the data-mining method subgroup discovery. Our study demonstrates the importance of data analytics for avoiding bias in catalysis design, and provides a recipe for finding best SAACs for various applications.

Implicit solvent effects in the determination of Brønsted–Evans–Polanyi relationships for heterogeneously catalyzed reactions

The Brønsted–Evans–Polanyi relationship derived for the water dissociation reaction within an implicit solvent approach is similar to that without such effects.

Prediction of metallic nanotube reactivity for H2O activation

The reactivity of metallic nanotubes toward the catalysis of water dissociation, a key step in the water gas shift reaction (WGSR), was analyzed through density functional theory (DFT) calculations. Water dissociation was studied on surfaces of nanotubes based on copper, gold and platinum, and also on platinum doped copper and gold nanotubes. Gold and copper nanotubes present activities that are similar to those of their corresponding extended surfaces but, in the case of the Pt(5,3) nanotube, a significant improvement in the activity is found when compared with the extended surfaces. In fact, the calculations predict the water dissociation to be spontaneous on Pt(5,3) with a low activation energy barrier. The platinum doping of gold and copper nanotubes leads to contrasting effects, i.e., with a slight increase of activity found on gold and a slight decrease of activity in the case of copper. The consideration of a Brönsted-Evans-Polanyi (BEP) relationship to estimate the activation energy barriers for the O-H bond break leads to a satisfactory agreement between estimated and explicitly calculated values which suggests the validity of the BEP relationship for qualitative predictions of the activities of metal nanotubes towards the water dissociation reaction.

Catalytic activity of transition metal doped Cu(111) surfaces for ethanol synthesis from acetic acid hydrogenation: a DFT study

The effects of transition metal dopants on Cu(111) surfaces for ethanol synthesis from acetic acid hydrogenation are investigated.

Effect of the Exchange-Correlation Potential on the Transferability of Brønsted-Evans-Polanyi Relationships in Heterogeneous Catalysis

As more and more accurate density functional methods emerge, the transferability of Brønsted-Evans-Polanyi (BEP) relationships obtained with previous models is an open question. In this work, BEP relationships derived from different density functional theory based calculations are analyzed to answer this question. In particular, BEP relationships linking the activation energy of O-H bond breaking reactions taking place on metallic surfaces with the adsorption energy of the reaction products are chosen as a case study. These relationships are obtained with the widely used Perdew-Wang (PW91) generalized gradient approximation (GGA) exchange-correlation functional and with the more accurate meta-GGA Tao-Perdew-Staroverov-Scuseria (TPSS) one. We provide compelling evidence that BEP relationships derived from PW91 and TPSS functionals are essentially coincidental. This finding validates previously published BEP relationships and indicates that the reaction activation energy barrier can be obtained by the determination of the energy reaction descriptor value at the less computationally demanding GGA level; an important aspect to consider in future studies aimed at the computational design of catalysts with improved characteristics.

Methanol dissociation on bimetallic surfaces: validity of the general Brønsted–Evans–Polanyi relationship for O–H bond cleavage

Density functional theory calculations were used to study the dissociation of the O–H bond in methanol on several bimetallic transition metal surfaces, composed of elements showing high or moderate activity towards this reaction, namely, Ni, Rh, Ru, Ir, Pd, Au, Zn and Cu.