New thermoset systems based on disulfide bonds were synthesized with self-healing capabilities. The self-healing mechanism is not related to disulfide–disulfide exchange reactions, but to thiol–disulfide exchange reactions that are pH-dependent. Stress relaxation experiments showed large relaxation for systems having PTM2 as a curing agent, which indicates that the system can rearrange its molecular structure as a mechanism to release stress. However, relaxation rates decreased for samples tested longer after production. This indicates the disappearance of thiol-groups probably caused by thiol–thiol oxidation.

The increasing availability of quantum-chemical data on surface reaction intermediates invites one to revisit unresolved mechanistic issues in heterogeneous catalysis. One such issue of particular current interest is the molecular basis of the Fischer–Tropsch reaction. Here we review current molecular understanding of this reaction that converts synthesis gas into longer hydrocarbons where we especially elucidate recent progress due to the contributions of computational catalysis. This perspective highlights the theoretical approach to heterogeneous catalysis that aims for kinetic prediction from quantum-chemical first principle data. Discussion of the Fischer–Tropsch reaction from this point of view is interesting because of the several mechanistic options available for this reaction. There are many proposals on the nature of the monomeric single C atom containing intermediate that is inserted into the growing hydrocarbon chain as well as on the nature of the growing hydrocarbon chain itself. Two dominant conflicting mechanistic proposals of the Fischer–Tropsch reaction that will be especially compared are the carbide mechanism and the CO insertion mechanism, which involve cleavage of the C–O bond of CO before incorporation of a CH_x species into the growing hydrocarbon chain (the carbide mechanism) or after incorporation into the growing hydrocarbon chain (the CO insertion mechanism). The choice of a particular mechanism has important kinetic consequences. Since it is based on molecular information it also affects the structure sensitivity of this particular reaction and hence influences the choice of catalyst composition. We will show how quantum-chemical information on the relative stability of relevant reaction intermediates and estimates of the rate constants of corresponding elementary surface reactions provides a firm foundation to the kinetic analysis of such reactions and allows one to discriminate between the different mechanistic options. The paper will be concluded with a short perspective section dealing with the needs for future research. Many of the current key questions on the physical chemistry as well as computational study of heterogeneous catalysis relate to particular topics for further research on the fundamental aspects of Fischer–Tropsch catalysis.

Carbon dioxide is a desired feedstock for platform molecules, such as carbon monoxide or higher hydrocarbons, from which we will be able to make many different useful, value-added chemicals. Its catalytic hydrogenation over abundant metals requires the amalgamation of theoretical knowledge with materials design. Here we leverage a theoretical understanding of structure sensitivity, along with a library of different supports, to tune the selectivity of methanation in the Power-to-Gas concept over nickel. For example, we show that carbon dioxide hydrogenation over nickel can and does form propane, and that activity and selectivity can be tuned by supporting different nickel particle sizes on various oxides. This theoretical and experimental toolbox is not only useful for the highly selective production of methane, but also provides new insights for carbon dioxide activation and subsequent carbon–carbon coupling towards value-added products thereby reducing the deleterious effects of this environmentally harmful molecule.

Indium oxide (In₂O₃) is a promising catalyst for selective CH₃OH synthesis from CO₂ but displays insufficient activity at low reaction temperatures. By screening a range of promoters (Co, Ni, Cu, and Pd) in combination with In₂O₃ using flame spray pyrolysis (FSP) synthesis, Ni is identified as the most suitable first-row transition-metal promoter with similar performance as Pd–In₂O₃. NiO–In₂O₃ was optimized by varying the Ni/In ratio using FSP. The resulting catalysts including In₂O₃ and NiO end members have similar high specific surface areas and morphology. The main products of CO₂ hydrogenation are CH₃OH and CO with CH₄ being only observed at high NiO loading (≥75 wt %). The highest CH₃OH rate (∼0.25 g_MeOH/(g_cat h), 250 °C, and 30 bar) is obtained for a NiO loading of 6 wt %. Characterization of the as-prepared catalysts reveals a strong interaction between Ni cations and In₂O₃ at low NiO loading (≤6 wt %). H₂-TPR points to a higher surface density of oxygen vacancy (O_v) due to Ni substitution. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electron paramagnetic resonance analysis of the used catalysts suggest that Ni cations can be reduced to Ni as single atoms and very small clusters during CO₂ hydrogenation. Supportive density functional theory calculations indicate that Ni promotion of CH₃OH synthesis from CO₂ is mainly due to low-barrier H₂ dissociation on the reduced Ni surface species, facilitating hydrogenation of adsorbed CO₂ on O_v.

Resolving the structure and composition of supported nanoparticles under reaction conditions remains a challenge in heterogeneous catalysis. Advanced configurational sampling methods at the density functional theory level are used to identify stable structures of a Pd8 cluster on ceria (CeO2) in the absence and presence of O2. A Monte Carlo method in the Gibbs ensemble predicts Pd-oxide particles to be stable on CeO2 during CO oxidation. Computed potential energy diagrams for CO oxidation reaction cycles are used as input for microkinetics simulations. Pd-oxide exhibits a much higher CO oxidation activity than metallic Pd on CeO2. This work presents for the first time a scaling relation for a CeO2-supported metal nanoparticle catalyst in CO oxidation: a higher oxidation degree of the Pd cluster weakens CO binding and facilitates the rate-determining CO oxidation step with a ceria O atom. Our approach provides a new strategy to model supported nanoparticle catalysts.