Oxygen reduction on chemically heterogeneous iron-containing nanoporous carbon: the effects of specific surface functionalities

Synthetic activated carbon containing iron and sulfur heteroatoms, obtained from polystyrene sulfonic acid-based organic salt, and commercial wood-based carbon containing phosphorous were tested as catalysts for oxygen reduction reactions. The carbons were characterized using adsorption of nitrogen, TA-MS, FTIR, XRD, XPS, potentiometric titration, SEM/EDX, and HR-TEM microscopy. The introduction of iron to the carbon resulted a marked electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline medium. A current density was higher than that on commonly used platinum modified carbon and number of electron transfer (~4e-) indicated a high ORR efficiency. This was accompanied by a high tolerance to methanol oxidation and a good long-term stability after 1500 potential cycles. The extensive surface characterization indicated the fast O2 adsorption and charge transfer was owed to the surface hydrophobicity, small pores and conductivity. The synergistic effect of porosity and specific iron species containing sulfur lead to high ORR activity and high kinetic current densities

Superior Performance of Copper Based MOF and Aminated Graphite Oxide Composites as CO₂ Adsorbents at Room Temperature

New composites Cu-BTC MOF and graphite oxide modified with urea (GO-U) are developed and tested as CO₂ adsorbents at room temperature. The composite containing GO-U with the highest nitrogen content exhibits an excellent CO₂ uptake (4.23 mmol/g) at dynamic conditions. The incorporation of GO-U into MOF changes the chemistry and microstructure of the parent MOF and results in synergistic features beneficial for CO₂ retention on the surface. To identify these features the initial and exhausted materials were extensively characterized from the points of view of their porosity and chemistry. Although the adsorption forces are relatively strong, the results indicate that CO₂ is mainly physisorbed on the composites at dry dynamic conditions at ambient temperature and pressure. The primary adsorption sites include small micropores specific for the composites, open Cu sites, and cage window sites

Electrochemical Reduction of Oxygen on Hydrophobic Ultramicroporous PolyHIPE Carbon

A new kind of polyHIPE (polymerized high internal phase emulsion)-based carbon derived from coreacted furfuryl alcohol and tannin was tested as an ORR catalyst. To understand the reduction process, the surface was extensively characterized from the point of view of texture and chemistry. The prepared materials show subtle differences in the chemistry but marked differences in the porosity. The best-performing sample had a very high volume of ultramicropores and the highest degree of defects on the surface. The oxygen was present on the surface mainly in epoxy and ether configurations. Those oxygen groups located in large pores promoted transfer of O₂ dissolved in water/electrolyte to small pores of the hydrophobic surface. There, a strong adsorption of oxygen was energetically favorable. This led to weakening of O–O bonds, subsequent dissociation of oxygen, and its reduction/protonation. The presented polyHIPE carbons show high electrochemical stability and better tolerance to methanol than Pt/C. High kinetic current density was measured on them

Graphene-Based Materials for the Fast Removal of Cytokines from Blood Plasma

There is a range of medical conditions, which include acute organ failure, bacterial and viral infection, and sepsis, that result in overactivation of the inflammatory response of the organism and release of proinflammatory cytokines into the bloodstream. Fast removal of these cytokines from blood circulation could offer a potentially efficient treatment of such conditions. This study aims at the development and assessment of novel biocompatible graphene-based adsorbents for blood purification from proinflammatory cytokines. These graphene-based materials were chosen on the basis of their surface accessibility for small molecules further facilitated by the interlayer porosity, which is comparable to the size of the cytokine molecules to be adsorbed. Our preliminary results show that graphene nanoplatelets (GnP) exhibit high adsorption capacity, but they cannot be used in direct contact with blood due to the risk of small carbon particle release into the bloodstream. Granulation of GnP using poly­(tetrafluoroethylene) as a binder eliminated an undesirable nanoparticle release without affecting the GnP surface accessibility for the cytokine molecules. The efficiency of proinflammatory cytokine removal was shown using a specially designed flow-through system. So far, GnP proved to be among the fastest acting and most efficient sorbents for cytokine removal identified to date, outperforming porous activated carbons and porous polymers