Beyond confinement effects in Fischer-Tropsch Co/CNT catalysts

Transforming electrochemical hydrogen Production: Tannic Acid-Boosted CoNi alloy integration with Multi-Walled carbon nanotubes for advanced bifunctional catalysis

The dimensions of alloy nanoparticles or nanosheets have emerged as a critical determinant for their prowess as outstanding electrocatalysts in water decomposition. Remarkably, the reduction in nanoparticle size results in an expanded active specific surface area, elevating reaction kinetics and showcasing groundbreaking potential. In a significant leap towards innovation, we introduced tannic acid (TA) to modify multi-walled carbon nanotubes (MWCNTs) and CoNi alloys. This ingenious strategy not only finely tuned the size of CoNi alloys but also securely anchored them to the MWCNTs substrate. The resulting synergistic "carbon transportation network" accelerated electron transfer during the reaction, markedly enhancing efficiency. Furthermore, the exceptional synergy of Co and Ni elements establishes Co0.84Ni1.69/MWCNTs as highly efficient electrocatalysts. Experimental findings unequivocally demonstrate that TA-Co0.84Ni1.69/MWCNTs require minimal overpotentials of 171 and 294 mV to achieve a current density of ± 10 mA cm-2. Serving as both anode and cathode for overall water splitting, TA-Co0.84Ni1.69/MWCNTs demand a low voltage of 1.66 V at 10 mA cm-2, maintaining structural integrity throughout extensive cyclic stability testing. These results propel TA-Co0.84Ni1.69/MWCNTs as promising candidates for future electrocatalytic advancements.

Synthesis and Growth of Green Graphene from Biochar Revealed by Magnetic Properties of Iron Catalyst

Understanding the mechanism of iron-catalyzed graphitization of biomass is an important step for the large-scale synthesis of green graphene. Although iron is known to be the most active transition metal for the catalytic graphitization of cellulose-derived biochar, the direct effect of the iron molecular structure on the formation of highly graphitic carbon remains elusive. Here, biochar was produced from pyrolysis of iron-impregnated cellulose at three different temperatures (1000, 1400, and 1800 °C). X-ray diffraction, X-ray photoelectron spectroscopy, and magnetic measurements were used to probe changes in biochar nanostructure catalyzed by the inclusion of iron. An increase of pyrolysis temperature led to an increase in the iron particle size and the degree of iron reduction, as well as the formation of larger graphitic carbon crystallite sizes, and these two attributes of iron were seen to positively affect the biochar graphitization usually challenging under 2000 °C.

Hydrogen spillover effects in the Fischer–Tropsch reaction over carbon nanotube supported cobalt catalysts

Support (CNTs) surface defect-induced hydrogen spillover significantly impacted the catalytic activity (turnover frequency, TOF) and methane selectivity evolution in cobalt-based Fischer–Tropsch synthesis.

Detailed formation process of Co@C catalysts and the influence of structural regulation on catalytic properties

Co@C is a novel class of catalysts with many structural advantages, such as highly dispersed active species, developed pore structure, and special encapsulated structure. Although considerable progress has been made in the development of new Co@C materials, research on the formation mechanism of these materials is lacking. Herein, the overall microcosmic structure of the Co@C catalyst was investigated by systematic characterization. Subsequently, a pseudo in situ method was employed to explore the detailed structure of the Co@C catalyst pyrolyzed at different temperatures. The special carbon environment of materials is essential for synthesizing materials during pyrolysis at high temperatures. Co ions were reduced to Co⁰ by the surrounding carbon atoms at a high temperature. In return, the surrounding carbon atoms were catalyzed by Co⁰ particles to form carbon nanotubes. However, with the obstruction of amorphous carbon atoms that are not in contact with Co⁰, the paths through which the carbon nanotubes move forward formed the porous structure of the catalyst, as well as the graphitic encapsulated structure. Further, the effects of pretreatment conditions on the structure and properties of the Co@C catalyst were studied systematically.