Transition metal phthalocyanine-modified shungite-based cathode catalysts for alkaline membrane fuel cell

The alkaline anion exchange membrane fuel cell (AEMFC) is one of the green solutions for the growing need for energy conversion technologies. For the first time, we propose a natural shungite based non-precious metal catalyst (NPMC) as an alternative cathode catalyst to Pt-based materials for AEMFCs application. The Co and Fe phthalocyanine (Pc)-modified shungite materials were prepared via pyrolysis and used for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) studies. The most promising ORR performance was observed in alkaline media for FePc-modified and acid-leached shungite-based NPMC material. The catalysts were also evaluated as cathode materials in a single cell AEMFC and peak power densities of 232 and 234 mW cm^?2 at 60 °C using H₂ and O₂ gases at 100% RH were observed for CoPc- and FePc-modified acid-treated materials, respectively.     

Water mediated modification of structure and physical chemical properties of nanocarbons

Considerable amount of water incapsulated in native shungite carbon (ShC) and its amphiphilic properties are originated from fullerene-like structure. We report on the study of ShC and its stable aqueous dispersion by high-resolution solid state ¹³С and ¹Н MAS NMR, and time-of-flight (TOF) mass spectrometry. ¹³С NMR spectrum changes substantially as ShC was transformed into aqueous dispersion: a narrow sp²-carbon signal (at 116 ppm) attributed to the basic structural unit (BSU) in the form of bowls is observed. Distance from carbon atoms in BSU to hydrogen atoms of water was estimated at  0.8 nm using cross-polarization technique. ¹H solid state NMR spectrum consists of two peaks at 0.40 and 3.16 ppm. They were assumed to be related to water complexes on BSU (0.40 ppm) and to adsorbed water (3.16 ppm). TOF mass spectra of the ShC aqueous dispersion showed maximum intensity at  284 m/z corresponding to the dominant structure of ShC.     

Diamagnetism of natural fullerene-like carbon

Carbon from shungite rocks from Karelia (Russia) displays an increase in diamagnetism between ca. 90 and 150 K. The diamagnetic effect is largest for samples that contain twisted graphene layers up to 100 nm across, preferentially oriented, and with nanometer-sized pores as seen in high-resolution transmission electron microscopy images. No increase in diamagnetism was observed for shungite rocks containing carbon with randomly oriented graphene layers. Such diamagnetism has been observed for doped fullerites but has not previously been reported for amorphous natural carbon.     

Pore structures in shungites as revealed by small-angle neutron scattering

The analysis of the small-angle neutron scattering data from shungites, one of the natural forms of carbon, is reported. Samples from different deposits are investigated. It is shown that shungites have a complex pore structure at a nanoscale of 1-100 nm depending on their origin. Along with it, common features, in particular, two-level organization at the given scale can be observed. The absorption of deuterated water by shungites is used to match the scattering from open pores and to separate the information about the open and closed porosity in the samples. The revealed structural units are compared with the previous experimental results obtained by the complementary techniques.     

Medium-range order in molecular materials: Fluctuation electron microscopy for detecting fullerenes in disordered carbons

During a fluctuation electron microscopy (FEM) study of disordered carbons, we found that samples containing C₆₀ exhibit a normalized variance peak at 7.1 nm⁻¹ that appears to be a unique indicator of tight curvature in layered materials. This peak is associated with the characteristic in-plane carbon–carbon bond distance of ∼0.14 nm in graphene. Diffraction from this spacing is normally forbidden in planar graphene (and graphite), but becomes allowed when the layer structure is interrupted. Such interruptions arise at the edges of graphite fragments and also when 5-rings are incorporated into a layer. We show that the curvature induced by a high density of 5-rings, such as that in C₆₀, can dominate the variance peak at 7.1 nm⁻¹. FEM simulations reveal that the variance peak at ∼7.1 nm⁻¹, which we label F₁, is one of several fullerene-signature peaks, with others occurring at Q values of 10.6 nm⁻¹ (F₂) and 12.4 nm⁻¹ (F₃). We conclude that FEM is a sensitive method for detecting dilute quantities of highly curved pentagon-rich fullerenes, such as C₆₀, when dispersed within disordered graphitic carbon.