Oxygen vacancies in Ru/TiO2 - drivers of low-temperature CO2 methanation assessed by multimodal operando spectroscopy

High-efficiency electrocatalytic nitrite reduction toward ammonia synthesis on CoP@TiO2 nanoribbon array

Electrochemical reduction of nitrite (NO₂^-) can satisfy the necessity for NO₂^- contaminant removal and deliver a sustainable pathway for ammonia (NH₃) generation. Its practical application yet requires highly efficient electrocatalysts to boost NH₃ yield and Faradaic efficiency (FE). In this study, CoP nanoparticle-decorated TiO₂ nanoribbon array on Ti plate (CoP@TiO₂/TP) is verified as a high-efficiency electrocatalyst for the selective reduction of NO₂^- to NH₃. When measured in 0.1 M NaOH with NO₂^-, the freestanding CoP@TiO₂/TP electrode delivers a large NH₃ yield of 849.57 μmol h^-1 cm^-2 and a high FE of 97.01% with good stability. Remarkably, the subsequently fabricated Zn-NO₂^- battery achieves a high power density of 1.24 mW cm^-2 while delivering a NH₃ yield of 714.40 μg h^-1 cm^-2.

Investigating the impact of TiO2 crystalline phases on catalytic properties of Ru/TiO2 for hydrogenolysis of polyethylene plastic waste

A series of TiO₂-supported Ru catalysts with different TiO₂ crystalline phases was synthesized and employed for the hydrogenolysis of polyethylene (PE). CO chemisorption, high-angle annular dark-field-scanning transmission electron microscopy, temperature-programmed reduction, and CO-Fourier transform infrared spectroscopy suggested that the degree of strong metal-support interactions (SMSIs) varied depending on the type of the TiO₂ phase and the reduction temperature, eventually influencing the catalysis of PE hydrogenolysis. Among the synthesized catalysts, Ru/TiO₂ with the rutile phase (Ru/TiO₂-R) exhibited the highest catalytic activity after high-temperature reduction at 500 °C, indicating that a certain degree of SMSI is necessary for ensuring high activity in PE hydrogenolysis. Ru/TiO₂-R could be successfully employed for the hydrogenolysis of post-consumer plastic wastes such as LDPE bottles to produce valuable chemicals (liquid fuel and wax) in high yields of 74.7%. This work demonstrates the possibility of harnessing the SMSIs in the design and synthesis of active catalysts for PE hydrogenolysis.

Controlling the Fe2O3-SiO2 interaction: The effect on the H2S selective catalytic oxidation and catalyst deactivation

Biogas utilization is one of the most promising options for reducing the consumption of fossil fuels for energy production, but the presence of H₂S represents a serious industrial and environmental problem. In this work, two different synthesis methods (sol-gel and incipient wetness impregnation) were used to synthesize iron oxide supported on silica catalysts (Fe₂O₃/SiO₂) with metal loadings ranging from 0.5 to 10 %wt. The catalysts were tested for the selective oxidation of H₂S, changing the operating conditions like O₂/H₂S (0.5-2.5), temperature (170-250°C), and water content (0-50%). The optimum condition was O₂/H₂S = 0.5 and no water at 230 °C with the conversion of approximately 100%, the selectivity of 97%, and the deactivation of 0.6%. A detailed characterization of the fresh and spent catalysts' surface revealed the presence of four deactivation mechanisms: metal surface reduction, oxygen vacancy loss, pore plugging, and sintering. Among the observed deactivation mechanisms, the sintering showed the highest impact on catalytic activity and deactivation. The sol-gel catalysts (SG) showed the highest metal-oxide/support interaction, which reduced the metal-oxide nanoparticles sintering compared with the incipient wetness impregnation method (IWI), reporting a lower sintering, higher activity, and selectivity, lower deactivation rates and lower sensitivity to the operating conditions. A catalytic cycle representing the possible surface intermediate states of the catalyst is proposed based on the performance and characterization results obtained.