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Oxygen reduction reaction (ORR) plays a critical position in direct methanol fuel cells. However, electrocatalytic materials currently utilized in ORR use a rare and expensive metal Pt, so it is vital to develop cathode catalysts with cheap and high ORR activity. Herein, chitosan, a natural material made from chitin, was employed as a complex precursor of carbon source and nitrogen (N) source to synthesize N-doped mesoporous biomass carbon ORR catalysts. Adding different pore agents regulated specific surface area and N type of catalysts. The relationship between the properties of the catalysts and their ORR electrocatalytic performance was investigated. It was luckily found that the addition of ferric nitrate as a pore-forming agent created a huge specific surface area of the N-doped mesoporous biomass carbon (1190 m 2 /g) significantly. More importantly, the synthesized catalyst was doped by whole pyridinic-N at high content (11.58 at %) and inhibited the two-electron reaction efficiently, promoted the four-electron reaction, and accelerated the ORR reaction rate. Furthermore, it provided significant catalytic activity with robust methanol tolerance, and notable cycle stability, indicating the practical applicability of the huge surface area, ultrahigh pyridinic-N-doped mesoporous biomass carbon catalyst.

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A new metal ion-loaded (Zr(IV), Al(III), Fe(III)) fibrous protein (MFP) was synthesized and characterized by surface charge (pH pzc ), surface morphology, and infrared spectrum. The pH pzc (point of zero charge) of MFP was located in alkaline zone, higher than that of fibrous protein (FP, 5.5−6.0) before impregnation. FTIR studies indicated that metal hydroxyl functional groups (M−OH, M representing surface metal ions of Zr(IV), Al(III), Fe(III)) played an important role in fluoride adsorption by MFP. The effects of pH, contact time, initial fluoride concentration, sorbent dosage and coexisting anions were investigated in order to clarify the adsorption properties of MFP for fluoride ion. The results suggested that MFP adsorbents exhibited reasonably significant fluoride removal over a wide range of pH values (4.0−9.0). Zr(IV)-loaded fibrous protein (ZrFP) had a maximum fluoride adsorption capacity up to 58.41 mg/g, and the maximum fluoride adsorption capacities were 37.51 and 15.24 mg/g for Al(III)-loaded fibrous protein (AlFP) and Fe(III)-loaded fibrous protein (FeFP), respectively, much higher than those of other common adsorbents. The sorption process was subjected to Langmuir and Freundlich isotherms, and Langmuir isotherm fit better than Freundlich. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS°indicated that the nature of fluoride sorption is spontaneous and exothermic. Kinetic studies indicated that the equilibrium was fast and was approached within 150 min, and the pseudo-second-order model could describe sorption of fluoride on MFP well.