Comparative FTIR study of the cobalt and iron porphyrin reactions with CO. Does cobalt porphyrin form a bis-carbonyl complex in the Ar matrix?

Investigation of Molecular Mechanism of Cobalt Porphyrin Catalyzed CO2 Electrochemical Reduction in Ionic Liquid by In-Situ SERS

This study explores the electrochemical reduction in CO₂ using room temperature ionic liquids as solvents or electrolytes, which can minimize the environmental impact of CO₂ emissions. To design effective CO₂ electrochemical systems, it is crucial to identify intermediate surface species and reaction products in situ. The study investigates the electrochemical reduction in CO₂ using a cobalt porphyrin molecular immobilized electrode in 1-n-butyl-3-methyl imidazolium tetrafluoroborate (BMI.BF4) room temperature ionic liquids, through in-situ surface-enhanced Raman spectroscopy (SERS) and electrochemical technique. The results show that the highest faradaic efficiency of CO produced from the electrochemical reduction in CO₂ can reach 98%. With the potential getting more negative, the faradaic efficiency of CO decreases while H₂ is produced as a competitive product. Besides, water protonates porphyrin macrocycle, producing pholorin as the key intermediate for the hydrogen evolution reaction, leading to the out-of-plane mode of the porphyrin molecule. Absorption of CO₂ by the ionic liquids leads to the formation of BMI·CO₂ adduct in BMI·BF₄ solution, causing vibration modes at 1100, 1457, and 1509 cm^-1. However, the key intermediate of CO2-· radical is not observed. The υ(CO) stretching mode of absorbed CO is affected by the electrochemical Stark effect, typical of CO chemisorbed on a top site.

Analysis of thermal decomposition of acidified sediments in gold plants and harmless disposal of it

In the present work, thermal decomposition of ASs in air was characterized by a combination of TG-DSC, XRD, and TG-FTIR. The treatment of generated toxic (CN)₂ gas was investigated as well. The result showed that the decomposition of Zn₂Fe(CN)₆ in ASs preferentially reacted with CuSCN leading to the early decomposition of ASs, in which a part of CuSCN decomposed into Cu₅FeS₄ or Cu₂S followed by being oxidized to sulfates and oxides as the temperature increased to 420 °C. For Zn₂Fe(CN)₆·3H₂O in ASs, the decomposition products below 500 °C include ZnS, ZnSO₄, Cu_xFe_yS_z, iron oxides and Zn(CN)₂; instead, Fe₃O₄, ZnSO₄ and ZnFe₂O₄ were formed. The FTIR and chemical quantitative analysis showed that nitrogen-containing gaseous products predominately contained (CN)₂, HCN and small amounts of NH₃ and NO_x. In view of toxic gases released, catalytic oxidation employing in-situ generation of roasting slag at 600 °C (AS1) can be effectively used for the conversion of (CN)₂ to N₂ under the optimal conditions of airflow rate of 0.7 L/min and AS1/ASs mass ratio of 0.5. Significantly, the ZnFe₂O₄ phase in AS1 completely disappeared and was converted to ZnSO₄ after the experiment, which facilitated the subsequent acid leaching, thereby achieving the synergistic treatment of exhaust gases and slag.