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Abstract

The development of effective catalysts for sustainable hydrogen production is essential for the gradual transition to low-emission technologies. In this thesis, we focus on an ab initio investigation of experimentally relevant catalysts for dry reforming of methane and the hydrogen evolution reaction. Our aim is to explore structure–activity relationships and provide valuable insights into the design of highly efficient catalysts.
First, we investigate the dry reforming of methane (CH₄ + CO₂ → 2CO + 2H₂) over Ni-based catalysts. We examine the origin of the experimentally observed differences between undoped and Mn-doped CeO₂/Ni catalysts through vibrational analysis and reaction mechanism studies. Metallic Ni is found to be active for the reaction but prone to carbon deposition, whereas NiO is inactive but resistant to carbon poisoning. Our results suggest that the key difference between undoped and Mn-doped catalysts lies in the oxidation state of Ni: the Mn-doped catalyst contains partially oxidized Ni, which retains its catalytic activity while exhibiting greater resistance to carbon deposition.

Next, we study the hydrogen evolution reaction on Pt- and Ru-based catalysts. For platinum, surface Pourbaix diagrams are constructed for both ideal surfaces and nanoparticle models, and kinetic analyses are performed on ideal surfaces. The results reveal higher reactivity for the nanoparticle models and a strong dependence of activation barriers on the coverage of chemisorbed H. For ruthenium, we compare the catalytic activity of the hcp and fcc crystal phases by examining close-packed ideal surfaces and Wulff-constructed nanoparticles. Interestingly, the close-packed surfaces exhibit an activity trend opposite to that observed experimentally for hcp- and fcc-structured nanoparticles. The high activity of fcc Ru catalysts is attributed to the presence of less stable facets on the nanoparticles.
Finally, we investigate models of supported Pt and Ru nanoparticles to compare conventional carbon supports with the highly effective TiON support. The latter is found to influence the catalysts in two ways: (i) it strengthens the adhesion of metal nanoparticles to the support, thereby enhancing their durability and resistance to agglomeration; and (ii) it slightly weakens hydrogen binding, thereby improving catalytic activity toward the hydrogen evolution reaction.