Exposed N and S Active Sites: An Indicator for Oxygen Reduction on Metal‐Free Yam‐Derived Porous Carbons

Abstract

Exploring efficient and low‐cost catalysts for the oxygen reduction reaction (ORR) is a key issue in the development of renewable energy devices such as fuel cells and metal−air batteries. The design and construct of advanced catalysts can be guided by identifying the sites with high activity. In this study, an indicative research study on the ORR of yam‐derived N and S self‐doped porous carbons (NSDCs) is presented. The NSDC optimized at 800 °C (NSDC800) with more exposed intrinsic N and S active sites shows a comparable ORR activity to the commercial Pt/C and sets the top level for metal‐free carbons, as well as high stability and tolerance to CO and methanol. Consequently, a homemade primary Al−air battery with NSDC800 demonstrates an open‐circuit potential of 1.66 V and a peak power density of 83 mW cm−2. With a series of NSDCs, the exposed intrinsic N and S sites (pyrrolic‐N, graphitic‐N, and thiophene‐S) are synergistically identified as the activity indicators for the ORR. This finding may provide an insight into the analysis of active sites and open an avenue for the synthesis and volume production of carbon‐based ORR catalysts with low cost and high activity.

Dual‐Functional NaCl Template Strategy towards Synthesis of Metal‐Free Sulfur/nitrogen co‐Doped Carbon Nanosheets Catalysts for Oxygen Reduction Reaction

“…It implies that the graphitic N and pyridinic N groups account for the majority. The S2p XPS spectra reveals that S atoms are in the form of oxidic‐S (‐C‐SO 4 ‐ (169.8 eV), ‐C‐SO 3 ‐ (168.3 eV), ‐C‐SO 2 ‐ (166.2 eV)), thiophenic‐S (S2p 1/2 (165.1 eV)and S2p 3/2 (163.9 eV)) and H 2 S (170.7 eV), as shown in Figure c and Figure S1e, and the thiophenic‐S is dominated in the sulfur species . Figure d shows that the percentages of the four types of N and thiophenic‐S, and it is easy to observe that the contents both of graphitic N and thiophenic‐S of S3/N‐CNS800 are more than those of S3/N‐CN800.…”

Supramolecular Iron Complex Formed Between Nitrogen Riched Phenanthroline Derivative and Iron With Improved Oxygen Reduction Activity in Alkaline Electrolyte

“…The porous features of Fe-PIPhen/C were further characterized by N 2 adsorption-desorption measurements. The N 2 adsorption-desorption isotherm of Fe-PIPhen/C is shown in Figure 3, it represents the type-III of N 2 adsorption/desorption isotherms with large specific surface areas and pore volumes (Fan et al, 2017). As summarized in Table 1, the BET surface area and the pore volume of the Vulcan XC-72 carbon and Fe-PIPhen/C are 108.665 m 2 /g, 1.338 cm 3 /g, and 77.849 m 2 /g, 0.90 cm 3 /g, respectively.…”

Green Crop Yam-Derived Carbons: Off-Plane Active Sites for Oxygen Electroreduction Identified by First-Principles

“…As one of the widely distributed and resource-rich green crop, yam has richened starch, protein, and other components, which has attracted great attention in catalysis . Yao et al developed nanoporous carbon microspheres obtained by hydrothermal carbonization and annealing of starch, featuring a high surface area and pore volume and performing good catalytic activities . However, owing to high-temperature pyrolysis during carbonization, the starch-derived carbons partially lose the typical spherical morphology of starch in nature.…”

“…28 Yao et al 29 developed nanoporous carbon microspheres obtained by hydrothermal carbonization and annealing of starch, featuring a high surface area and pore volume and performing good catalytic activities. 30 However, owing to high-temperature pyrolysis during carbonization, the starch-derived carbons partially lose the typical spherical morphology of starch in nature. It is believed that the spherical structure of carbons features a curved surface structure and good surface accessibility, which can substantially boost ORR performance.…”