CO2 Hydrogenation on ZrO2/Cu(111) Surfaces: Production of Methane and Methanol

First-principles study of CO2 hydrogenation on Cd-doped ZrO2: Insights into the heterolytic dissociation of H2

Cd-doped ZrO2 catalyst has been found to have high selectivity and activity for CO2 hydrogenation to methanol. In this work, density functional theory calculations were carried out to investigate the microscopic mechanism of the reaction. The results show that Cd doping effectively promotes the generation of oxygen vacancies, which significantly activate the CO2 with stable adsorption configurations. Compared with CO2, gaseous H2 adsorption is more difficult, and it is mainly dissociated and adsorbed on the surface as [HCd-HO]* or [HZr-HO]* compact ion pairs, with [HCd-HO]* having the lower energy barrier. The reaction pathways of CO2 to methanol has been investigated, revealing the formate path as the dominated pathway via HCOO* to H2COO* and to H3CO*. The hydrogen anions, HCd* and HZr*, significantly reduce the energy barriers of the reaction.

Nature of Zirconia on a Copper Inverse Catalyst Under CO2 Hydrogenation Conditions

The growing concern over the escalating levels of anthropogenic CO2 emissions necessitates effective strategies for its conversion to valuable chemicals and fuels. In this research, we embark on a comprehensive investigation of the nature of zirconia on a copper inverse catalyst under the conditions of CO2 hydrogenation to methanol. We employ density functional theory calculations in combination with the Grand Canonical Basin Hopping method, enabling an exploration of the free energy surface including a variable amount of adsorbates within the relevant reaction conditions. Our focus centers on a model three-atom Zr cluster on a Cu(111) surface decorated with various OH, O, and formate ligands, noted Zr3Ox (OH)y (HCOO)z/Cu(111), revealing major changes in the active site induced by various reaction parameters such as the gas pressure, temperature, conversion levels, and CO2/H2 feed ratios. Through our analysis, we have unveiled insights into the dynamic behavior of the catalyst. Specifically, under reaction conditions, we observe a large number of composition and structures with similar free energy for the catalyst, with respect to changing the type, number, and binding sites of adsorbates, suggesting that the active site should be regarded as a statistical ensemble of diverse structures that interconvert.

Cu Facet-Dependent Elementary Surface Reaction Kinetics of CO2 Hydrogenation to Methanol Catalyzed by ZrO2/Cu Inverse Catalysts

ZrO2-Cu-based catalysts are active in catalyzing the hydrogenation of CO2 to methanol. Herein, we report Cu facet effects on the catalytic performance of ZrO2/Cu inverse catalysts in CO2 hydrogenation to methanol using various Cu nanocrystals with well-defined Cu morphologies and facets. The ZrO2-Cu interface is the active site, in which the ZrO2-Cu{100} and ZrO2-Cu{110} interfaces exhibit similar apparent activation energies of ∼42.6 kJ/mol, smaller than that of the ZrO2-Cu{111} interface (∼64.5 kJ/mol). Temporal in situ diffuse reflectance infrared Fourier transform spectroscopy characterization results identify the bridge formate hydrogenation as the rate-determining elementary surface reaction under typical reaction temperatures, whose activation energy is similar at the ZrO2-Cu{100} (∼36.3 kJ/mol) and ZrO2-Cu{110} (∼40.5 kJ/mol) interfaces and larger at the ZrO2-Cu{111} interface (∼54.5 kJ/mol). This fundamental understanding suggests Cu facet engineering as a promising strategy to improve the catalytic performance of ZrO2/Cu inverse catalysts for CO2 hydrogenation to methanol.

Facile solvothermal synthesis of nitrogen-doped SnO2 nanorods towards enhanced photocatalysis

Heteroatom doping has proved to be one of the most effective approaches to further improve the photocatalytic activities of semiconducting oxides originating from the modulation of their electronic structures. Herein, nitrogen-doped SnO₂ nanorods were synthesized via facile solvothermal processes using polyvinylpyrrolidone (PVP) as a dispersing agent and ammonium water as the N source, respectively. Compared with pure SnO₂ sample, the as-synthesized nitrogen-doped SnO₂ nanorods demonstrated enhanced photocatalytic performances, evaluated by the degradation of rhodamine B (RhB), revealing the effectiveness of nitrogen doping towards photocatalysis. In particular, the optimal photocatalyst (using 0.6 g PVP and 1 mL ammonia water) could achieve up to 86.23% pollutant removal efficiency under ultraviolet (UV) light irradiation within 150 min, showing 17.78% higher efficiency than pure SnO₂. Detailed structural and spectroscopic characterization reveals the origin of activity enhancement of nitrogen-doping SnO₂ in contrast with pure SnO₂. Specifically, the bandgap and the morphologies of nitrogen-doped SnO₂ have changed with more chemisorbed sites, which is supposed to result in the enhancement of photocatalytic efficiency. Moreover, the possible formation mechanism of nitrogen-doped SnO₂ nanorods was discussed, in which PVP played a crucial role as the structure orientator.