Carbon-Encapsulated Iron Nanoparticles as a Magnetic Modifier of Bioanode and Biocathode in a Biofuel Cell and Biobattery

This work demonstrates the application of magnetic carbon-encapsulated iron nanoparticles (CEINs) for the construction of bioelectrodes in a biobattery and a biofuel cell. It has been shown that carbon-encapsulated iron nanoparticles are a suitable material for the immobilization of laccase (Lc) and 1,4-naphthoquinone (NQ) and fructose dehydrogenase (FDH). The system is stable; no leaching of the enzyme and mediator from the surface of the modified electrode was observed. The onset of the catalytic reduction of oxygen to water was at 0.55 V, and catalytic fructose oxidation started at −0.15 V. A biobattery was developed in which a zinc plate served as the anode, and the cathode was a glassy carbon electrode modified with carbon-encapsulated iron nanoparticles, laccase in the Nafion (Nf) layer. The maximum power of the cell was ca. 7 mW/cm2 at 0.71 V and under external resistance of 1 kΩ. The open-circuit voltage (OCV) for this system was 1.51 V. In the biofuel cell, magnetic nanoparticles were used both on the bioanode and biocathode to immobilize the enzymes. The glassy carbon bioanode was coated with carbon-encapsulated iron nanoparticles, 1,4-naphthoquinone, fructose dehydrogenase, and Nafion. The cathode was modified with carbon-encapsulated magnetic nanoparticles and laccase in the Nafion layer. The biofuel cell parameters were as follows: maximum power of 78 µW/cm2 at the voltage of 0.33 V and under 20 kΩ resistance, and the open-circuit voltage was 0.49 V. These enzymes worked effectively in the biofuel cell, and laccase also effectively worked in the biobattery

Extraordinary Adsorption of Methyl Blue onto Sodium-Doped Graphitic Carbon Nitride

Herein, the adsorption performance of sodium-doped graphitic carbon nitride in relation to the removal of methyl blue is investigated. The adsorbent was synthesized via the direct thermal polycondensation of cyanamide in the presence of sodium chloride. The inclusion of sodium in graphitic carbon nitride resulted in a substantial improvement of its adsorption capacity and adsorption kinetics. The maximum capacity for methyl blue was at least 8 times higher in comparison to commercial activated carbon and even 36 times higher than in the case of undoped material. The obtained adsorbents had very low porosity, and the resultant high adsorption capacities, as determined from the experiments, pointed to the extraordinary adsorption. Moreover, the equilibrium of the adsorption process was reached at the contact time less than 5 min. The obtained adsorbent was thoroughly investigated by means of various physical and chemical analyses. Additionally, the regeneration studies of the spent adsorbents were carried out

Graphitic Carbon Nitride Doped with the s‑Block Metals: Adsorbent for the Removal of Methyl Blue and Copper(II) Ions

The synthesis of graphitic carbon nitride (g-C₃N₄) doped with s-block metals is described. The materials were synthesized via thermal polycondensation of cyanamide and the appropriate metal chloride. The inclusion of the metal precursor strongly influenced the surface chemistry features as well as the textural, morphological, and structural properties of the g-C₃N₄. The doping of g-C₃N₄with s-block metals markedly enhanced its adsorption performance, which was studied during the removal of two model solutes (methyl blue and copper ions) from aqueous solutions. The maximum adsorption capacity for the organic dye was increased by 680 times after the doping process. The uptake of copper­(II) increased ca. 30 times for the doped g-C₃N₄. The improvement of the adsorption performance is discussed in terms of the surface chemistry and textural features