Transforming Hair into Heteroatom‐Doped Carbon with High Surface Area

Abstract

Herein, a unique approach to dispose of human hair by pyrolizing it in a regulated environment is presented, yielding highly porous, conductive hair carbons with heteroatoms and high surface area. α-keratin in the protein network of hair serves as a precursor for the heteroatoms and carbon. The carbon framework is ingrained with heteroatoms such as nitrogen and sulfur, which otherwise are incorporated externally through energy-intensive, hazardous, chemical reactions using proper organic precursors. This judicious transformation of organic-rich waste not only addresses the disposal issue, but also generates valuable functional carbon materials from the discard. This unique synthesis strategy involving moderate activation and further graphitization enhances the electrical conductivity, while still maintaining the precious heteroatoms. The effect of temperature on the structural and functional properties is studied, and all the as-obtained carbons are applied as metal-free catalysts for the oxygen reduction reaction (ORR). Carbon graphitized at 900 °C emerges as a superior ORR electrocatalyst with excellent electrocatalytic performance, high selectivity, and long durability, demonstrating that hair carbon can be a promising alternative for costly Pt-based electrocatalysts in fuel cells. The ORR performance can be discussed in terms of heteroatom doping, surface properties, and electrical conductivity of the resulting porous hair carbon materials.

The enhanced electrocatalytic activity of okara-derived N-doped mesoporous carbon for oxygen reduction reaction

“…Examples including cotton [7], pollen grains [8], and sawdust [9] have been used as precursors for various carbon based catalysts, and silk [10], pulse flour [11], honey [12], hair [13] and egg white [14] for the preparation of nitrogen-doped ORR catalysts by pyrolysis and post activations. However, the ORR performance of these catalysts in acid [10] or alkaline [11e14] medium remains lower than Pt/C catalysts, and from a practical point of view commercially uncompetitive.…”

Nitrogen-Doped Hollow Carbon Spheres with Embedded Co Nanoparticles as Active Non-Noble-Metal Electrocatalysts for the Oxygen Reduction Reaction

“…The potentials of all the electrochemical test results were transferred to the reversible hydrogen electrode (RHE). The relationship between E(vs. RHE) and E(vs. SCE) is shown as follows: E(vs.RHE) = E(vs.SCE) + E SCE + 0.0591 pH (1) where the E SCE at 25 • C is 0.2415 and the pH of 0.1 M KOH is considered as 13. Cyclic voltammetry (CV) or linear sweep voltammetry (LSV) measurements were carried out with a rotating disk electrode (RDE), and a rotating ring disk electrode (RRDE) was used as the working electrode for dual-electrode CV measurements.…”

“…In recent years, fuel cells have been attracting lots of attention due to their high energy conversion efficiency for converting chemical energy into electricity [1][2][3][4][5]. The entire reaction process occurring in fuel cells contains two half-reactions; one is the oxygen reduction reaction (ORR) at the cathode and the other is the hydrogen oxidation reaction (HOR) taking place at the anode.…”

Nitrogen-doped porous carbon derived from citric acid and urea with outstanding supercapacitance performance

“…Previous studies have demonstrated that the surface N-containing functionalities can give ACs acid/base characters, therefore playing a critical role in enhancing capacitance performance by providing pseudocapacitance via reversible redox reaction together with improving wettability between electrodes and electrolytes [23][24][25]. Popular strategies for the synthesis of N-doped ACs (NACs) include the direct carbonization approach, in which N-rich carbon precursors are directly pyrolyzed at high temperature [26], and the post-treatment approach, 4 which attempts to treat carbon with N-containing dopants (such as ammonia, amine, or urea) [11,25,27,28]. The latter approach can maintain the properties of the bulk material, but is time-consuming and results in heterogeneity of N-doping.…”