1 3
facile method to prepare nitrogen-rich carbon nano-onions from collagen to use as
an ORR electrocatalyst. They used goat skin wastes as a source of collagen. Electrochemical measurements demonstrated that the electrocatalytic activity of the prepared carbon samples is significantly comparable to that of commercially available
20% Pt/C electrocatalyst. The best electrocatalytic performance was observed for the
carbon sample synthesized at 750 °C for 8 h with an onset potential of −50 mV vs.
Ag/AgCl while comparing to 81 mV for 20% Pt/C. The electrocatalyst with higher
pyridinic nitrogen content exhibited an effective four-electron transfer ORR mechanism with a current density that is almost comparable to commercial Pt/C. The main
driving force enhancing ORR performance is the existence of the pyridinic nitrogen
atoms, which act as active sites as well as delivering net positive charge on the adjacent carbon atoms to facilitate oxygen adsorption along with the attraction of electrons from the anode. Furthermore, the nitrogen-rich carbon nano-onion-based electrocatalysts displayed outstanding durability performance in the alkaline medium as
well as superior methanol tolerance as compared with the 20% Pt/C.
Laccases are known as MCOs that are usually found in bacteria, fungi, and plants.
They can couple the one-electron oxidation of four substrate equals with four-electron reduction of an oxygen molecule to water. The electroreduction mechanism
happens by following a ping-pong mechanism. Oxidation of the substrates takes
place near the solvent-accessible T1 site. The electrons are then transferred through
the protein by following the Cys–His pathway over a distance of ∼12 Å to the trinuclear copper center where the ORR takes place. Luque et al. [56] reported the
synthesis of an unprecedented electrically active silica-encapsulated laccase material through a facile and eco-friendly one-pot biosilicification process and used for
the ORR for the first time. The one-pot biosilicification preparation facilitated the
lodging of the enzymes in the highly active alignments required for direct transfer of
the electrons of T1 redox centers.
As a result, the biosilicified laccase material that is deposited on the nickel electrodes displayed an effective bioelectrocatalytic reduction of oxygen, delivering
an outstanding current density of up to 0.94 mA/cm
2
and good long-term stability
properties (Fig. 4).
To design a metal-free ORR electrocatalyst, Chen et al. [57] reported a novel
strategy for preparing nitrogen-doped carbon nanomaterial-based electrocatalysts by
utilizing pyrolysis of the protein-enriched enoki mushroom at 900 °C, along with
carbon nanotubes as an inserting matrix and conductive agent. The mushrooms are
an abundantly available, renewable biomass source and are amino acid-rich. They
behave as a single precursor material for both carbon and heteroatoms, thus avoiding the utilization of complicated chemicals in the preparation method. It was found
that numerous forms of nitrogen (graphitic, pyrrolic and nitrile) were inserted into
the carbon molecular skeleton of the product, which displayed excellent ORR electrocatalytic performance as well as better durability behavior in alkaline medium
compared with those in acidic medium. The onset potential of the electrocatalyst
obtained in this study was about 0.94 V in the alkaline medium, which is comparable
with state-of-the-art Pt/C electrocatalysts (0.98 V). Remarkably, the measured ORR
half-wave potential of the prepared electrocatalyst was found to be 0.81 V in alkaline medium, which is slightly lower than that of the 20 wt% Pt/C electrocatalysts
246
Reprinted from the journal
Topics in Current Chemistry (2020) 378:43
facile method to prepare nitrogen-rich carbon nano-onions from collagen to use as
an ORR electrocatalyst. They used goat skin wastes as a source of collagen. Electrochemical measurements demonstrated that the electrocatalytic activity of the prepared carbon samples is significantly comparable to that of commercially available
20% Pt/C electrocatalyst. The best electrocatalytic performance was observed for the
carbon sample synthesized at 750 °C for 8 h with an onset potential of −50 mV vs.
Ag/AgCl while comparing to 81 mV for 20% Pt/C. The electrocatalyst with higher
pyridinic nitrogen content exhibited an effective four-electron transfer ORR mechanism with a current density that is almost comparable to commercial Pt/C. The main
driving force enhancing ORR performance is the existence of the pyridinic nitrogen
atoms, which act as active sites as well as delivering net positive charge on the adjacent carbon atoms to facilitate oxygen adsorption along with the attraction of electrons from the anode. Furthermore, the nitrogen-rich carbon nano-onion-based electrocatalysts displayed outstanding durability performance in the alkaline medium as
well as superior methanol tolerance as compared with the 20% Pt/C.
Laccases are known as MCOs that are usually found in bacteria, fungi, and plants.
They can couple the one-electron oxidation of four substrate equals with four-electron reduction of an oxygen molecule to water. The electroreduction mechanism
happens by following a ping-pong mechanism. Oxidation of the substrates takes
place near the solvent-accessible T1 site. The electrons are then transferred through
the protein by following the Cys–His pathway over a distance of ∼12 Å to the trinuclear copper center where the ORR takes place. Luque et al. [56] reported the
synthesis of an unprecedented electrically active silica-encapsulated laccase material through a facile and eco-friendly one-pot biosilicification process and used for
the ORR for the first time. The one-pot biosilicification preparation facilitated the
lodging of the enzymes in the highly active alignments required for direct transfer of
the electrons of T1 redox centers.
As a result, the biosilicified laccase material that is deposited on the nickel electrodes displayed an effective bioelectrocatalytic reduction of oxygen, delivering
an outstanding current density of up to 0.94 mA/cm
2
and good long-term stability
properties (Fig. 4).
To design a metal-free ORR electrocatalyst, Chen et al. [57] reported a novel
strategy for preparing nitrogen-doped carbon nanomaterial-based electrocatalysts by
utilizing pyrolysis of the protein-enriched enoki mushroom at 900 °C, along with
carbon nanotubes as an inserting matrix and conductive agent. The mushrooms are
an abundantly available, renewable biomass source and are amino acid-rich. They
behave as a single precursor material for both carbon and heteroatoms, thus avoiding the utilization of complicated chemicals in the preparation method. It was found
that numerous forms of nitrogen (graphitic, pyrrolic and nitrile) were inserted into
the carbon molecular skeleton of the product, which displayed excellent ORR electrocatalytic performance as well as better durability behavior in alkaline medium
compared with those in acidic medium. The onset potential of the electrocatalyst
obtained in this study was about 0.94 V in the alkaline medium, which is comparable
with state-of-the-art Pt/C electrocatalysts (0.98 V). Remarkably, the measured ORR
half-wave potential of the prepared electrocatalyst was found to be 0.81 V in alkaline medium, which is slightly lower than that of the 20 wt% Pt/C electrocatalysts
246
Reprinted from the journal
Topics in Current Chemistry (2020) 378:43