Heat treated Tethered Iron Phthalocyanine Carbon Nanotube-based Catalysts for Oxygen Reduction Reaction in Hybrid Fuel Cells

Pyridine Grafted on SnO2 -Loaded Carbon Nanotubes Acting as Cocatalyst for Highly Efficient Electroreduction of CO2

Sn-based electrocatalysts have shown great potential in the future industrial application of CO₂ electroreduction (CO₂ ER) to C₁ products due to their non-toxicity and low price. However, it is a great challenge to fabricate a Sn-based electrocatalytic system with high performance and stability. Herein, grafted pyridine was innovatively coupled with SnO₂ to construct an organic-inorganic composite (SnO₂ /Py-CNTO) for highly efficient CO₂ ER. The detailed studies showed that pyridine and protonated pyridine coexist on the surface of SnO₂ /Py-CNTO, and both play distinctive roles in promoting the selectivity of CO₂ ER. Benefiting from the merits, SnO₂ /Py-CNTO delivered an excellent faradaic efficiency (FE) of 96 % for CO₂ ER at -1.29 V_RHE where the HCOOH production with 85 % FE dominated, and good stability for 32 h electrolysis. The theoretical calculations showed that protonated pyridine not only facilitates the CO₂ adsorption and HCOOH desorption, but also significantly reduces the limiting potential for the conversion of CO₂ to HCOOH.

Degradation of carbamazepine by MWCNTs-promoted generation of high-valent iron-oxo species in a mild system with O-bridged iron perfluorophthalocyanine dimers

Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine (CBZ). However, metal phthalocyanine tends to undergo their own dimerization or polymerization, thereby reducing their activity points and affecting their catalytic properties. In this study, a catalytic system consisting of O-bridged iron perfluorophthalocyanine dimers (FePcF₁₆-O-FePcF₁₆), multi-walled carbon nanotubes (MWCNTs) and H₂O₂ was proposed. The results showed MWCNTs loaded with FePcF₁₆-O-FePcF₁₆ can achieve excellent degradation of CBZ with smaller dosages of FePcF₁₆-O-FePcF₁₆ and H₂O₂, and milder reaction temperatures. In addition, the results of experiments revealed the reaction mechanism of non-hydroxyl radicals. The highly oxidized high-valent iron-oxo (Fe(IV)=O) species was the main reactive species in the FePcF₁₆-O-FePcF₁₆/MWCNTs/H₂O₂ system. It is noteworthy that MWCNTs can improve the dispersion of FePcF₁₆-O-FePcF₁₆, contributing to the production of highly oxidized Fe(IV)=O. Then, the pathway of CBZ oxidative degradation was speculated, and the study results also provide new ideas for metal phthalocyanine-loaded carbon materials to degrade emerging pollutants.

Enhancing CO2 Electroreduction with Au/Pyridine/Carbon Nanotubes Hybrid Structures

Selective electrochemical reduction of CO₂ by using renewable electricity has received considerable attention because of the potential to convert a harmful greenhouse gas into useful chemicals. A high-performance electrocatalyst for CO₂ reduction is constructed based on metal nanoparticles/organic molecule hybrid materials. On the nanoscale, Au nanoparticles are uniformly anchored on carbon nanotubes to afford substantially increased current density, improved selectivity for CO, and enhanced stability. On the molecular level, the catalytic performance is further enhanced by introducing axial pyridine groups to the surface of the carbon nanotubes. The resulting hybrid catalyst exhibits around 93 % faradaic efficiency for CO production over a wide potential range (-0.58 to -0.98 V), a high mass activity of 251 A g_Au ^-1 at -0.98 V in aqueous solution at near-neutral pH, and strong stability with continuous electrolysis for 10 h at -0.58 V. DFT calculations indicate that the synergistic effects of Au and axial pyridine could dramatically stabilize the key intermediate (*COOH) formed in the rate-limiting step of CO₂ reduction, which effectively lowers the overpotential.