Glucose-derived carbon materials with tailored properties as electrocatalysts for the oxygen reduction reaction

Abstract

Nitrogen-doped biomass-derived carbon materials were prepared by hydrothermal carbonization of glucose, and their textural and chemical properties were subsequently tailored to achieve materials with enhanced electrochemical performance towards the oxygen reduction reaction. Carbonization and physical activation were applied to modify the textural properties, while nitrogen functionalities were incorporated via different N-doping methodologies (ball milling and conventional methods) using melamine. A direct relationship between the microporosity of the activated carbons and the limiting current density was found, with the increase of microporosity leading to interesting improvements of the limiting current density. Regardless of the doping method used, similar amounts of nitrogen were incorporated into the carbon structures. However, significant differences were observed in the nitrogen functionalities according to the doping method applied: ball milling appeared to originate preferentially quaternary and oxidized nitrogen groups, while the formation of pyridinic and pyrrolic groups was favoured by conventional doping. The onset potential was improved and the two-electron mechanism of the original activated sample was shifted closer to a four-electron pathway due to the presence of nitrogen. Interestingly, the high pyridinic content related to a high ratio of pyridinic/quaternary nitrogen results in an increase of the onset potential, while a decrease in the quaternary/pyrrolic nitrogen ratio favors an increase in the number of electrons. Accordingly, the electrocatalyst with the highest performance was obtained from the activated sample doped with nitrogen by the conventional method, which combined the most appropriate textural and chemical properties: high microporosity and adequate proportion of the nitrogen functionalities.

The Role of Lone‐Pair Electrons in Pt–N Interactions for the Oxygen Reduction Reaction in Polymer Exchange Membrane Fuel Cells

“…Along with nitrogen precursors such as pyridine and urea, large quantities of N‐functionalized carbon material could be synthesized by mechanochemical ball milling. Recently, some research groups have succeeded in synthesizing N‐doped carbon by using ball milling with melamine for use as a catalyst in an energy conversion system . This scalable strategy is advantageous for the simple modification of pristine carbon black to edge‐N‐doped carbon as well as to achieve a high N doping concentration (≈10 wt %); therefore, it is possible to use the N‐doped carbon from ball milling as a catalyst support.…”

“…Recently, some research groups have succeeded in synthesizing Ndoped carbon by using ball milling with melamine for use as a catalysti na ne nergy conversion system. [27][28][29] This scalable strategyisadvantageous for the simple modification of pristine carbon black to edge-N-doped carbon as well as to achievea high Nd oping concentration(% 10 wt %);t herefore, it is possible to use the N-doped carbon from ball milling as ac atalyst support.…”

Synthesis of amorphous and graphitized porous nitrogen-doped carbon spheres as oxygen reduction reaction catalysts

“…The amount Table 6: ORR onset potentials (potential value at 0.1 mA•cm −2 ) of the NCS and g-NCS catalysts in the ORR measurements in Figure 8. of pyridinic sites, which is often correlated with the ORR activity of nitrided carbon materials [16,[22][23][24][25], is highest for the NCS-700 catalyst and decreases with higher nitriding tempera-tures. This is opposite to the trend of the ORR activity, which increases with nitriding temperature (Table 2).…”

“…A variety of N bonding configurations can be formed within the carbon lattice [8], among them the pyridinic and quarternary (also: graphitic) nitrogen bonding configurations were assumed as origin of the ORR activity of these N-doped carbon materials [16]. The exact nature of the active site is controversially discussed; some researchers ascribe the ORR activity to graphitic nitrogen sites [17][18][19][20][21], while others propose pyridinic nitrogen as more important [16,[22][23][24][25][26]. Previous results of our groups indicate that the ORR activity of nitrided carbon is dominated by the carbon edge atoms of micropores in graphenic structures and the electronic structure of those atoms which is additionally modified by low-level N-doping [26,27].…”

Hydrothermal Carbon/Carbon Nanotube Composites as Electrocatalysts for the Oxygen Reduction Reaction

“…HTCs are commonly made up of spherical particles, which size can be controlled by modifying the synthesis conditions: concentration and the type of saccharide precursor and temperature and time of the hydrothermal treatment [20]. Nevertheless, the chemical properties of HTCs need to be modified in order to approach the outstanding electrochemical performance of Pt-electrocatalyst reference materials [23,24]. These modifications can be achieved by the incorporation of heteroatoms like nitrogen, sulfur, phosphorus, or boron and/or advanced carbon materials like graphene oxide or carbon nanotubes (CNTs) [9,12,13,17,[25][26][27][28].…”