Facile Synthesis of N-Doped Graphene-Like Carbon Nanoflakes as Efficient and Stable Electrocatalysts for the Oxygen Reduction Reaction

Abstract

A series of N-doped carbon materials (NCs) were synthesized by using biomass citric acid and dicyandiamide as renewable raw materials via a facile one-step pyrolysis method. The characterization of microstructural features shows that the NCs samples are composed of few-layered graphene-like nanoflakes with controlled in situ N doping, which is attributed to the confined pyrolysis of citric acid within the interlayers of the dicyandiamide-derived g-C3N4 with high nitrogen contents. Evidently, the pore volumes of the NCs increased with the increasing content of dicyandiamide in the precursor. Among these samples, the NCs nanoflakes prepared with the citric acid/dicyandiamide mass ratio of 1:6, NC-6, show the highest N content of ~6.2 at%, in which pyridinic and graphitic N groups are predominant. Compared to the commercial Pt/C catalyst, the as-prepared NC-6 exhibits a small negative shift of ~66 mV at the half-wave potential, demonstrating excellent electrocatalytic activity in the oxygen reduction reaction. Moreover, NC-6 also shows better long-term stability and resistance to methanol crossover compared to Pt/C. The efficient and stable performance are attributed to the graphene-like microstructure and high content of pyridinic and graphitic doped nitrogen in the sample, which creates more active sites as well as facilitating charge transfer due to the close four-electron reaction pathway. The superior electrocatalytic activity coupled with the facile synthetic method presents a new pathway to cost-effective electrocatalysts for practical fuel cells or metal–air batteries.

Mesoporous Ternary Nitrides of Earth-Abundant Metals as Oxygen Evolution Electrocatalyst

“…The RDE measurements confirmed that FePc shows a high intrinsic ORR activity (Fig. S10), superior to commercial Pt/C in 0.1 M KOH [65,66]. Figure 6b displays the charge polarization curves of the two air electrodes (FePc + Ni 3 FeN and Pt/C + RuO 2 ) in ZAB, implying a better charge performance of Ni 3 FeN than RuO 2 as confirmed by its higher current densities at the same potential.…”

A review of oxygen reduction mechanisms for metal-free carbon-based electrocatalysts

“…9 Subsequently, N-doped graphene and graphitic flakes were extensively synthesized and most reported samples can efficiently electrocatalyze the ORR via a four-electron pathway in alkaline fuel cells, which possessed better catalytic activity, stability, and tolerance to methanol crossover effect than Pt/C. [11][12][13][14][15] Following this pioneering work, various heteroatom-doped carbon materials were investigated, such as B-doped CNTs or graphene (BG), 16,17 sulfur-doped graphene (SG), [18][19][20][21] phosphorous-doped graphite layers, 22 iodine-doped graphene 23 , and edge-halogenated (Cl, Br or I) graphene nanoplatelets (GnPs). 24 For example, Antonietti's group developed mesoporous N-doped carbon materials with high surface area of 1500 m 2 g −1 by carbonization of nucleobases dissolved in an all-organic ionic liquid.…”

Preparation of chrome-tanned leather shaving-based hierarchical porous carbon and its capacitance properties

“…51,52 These peaks are attributed to the C]O group (the 1st), the carbonyl oxygen atom in the ester, the amide in the hydroxyl or ether, the anhydride and the carbonyl oxygen atom (the 2nd), the ether oxygen atom in the ester and anhydride (the 3rd) and the atoms in the oxygen carboxyl group (the 4th). 46,47 Similarly, the co-existence of pyridine nitrogen (398.3 eV), pyrrole/pyridone-N (400.2 eV) and pyridine-N-oxygen (402.7 eV) Table 1 Specific surface areas and pore volumes of CTSPC-2 and CTSHPC-x in CTSHPC-2 is demonstrated in the N1s spectrum (Fig. 7d).…”

“…The reason for this is that KOH activation may result in the loss of doped nitrogen content, which is similar to the reported literature. [45][46][47][48][49] In order to further determine the surface chemical composition of CTSHPC-2 carbon material, the C1s, O1s, and N1s spectra of the samples were carefully analyzed by the peak tting method, as shown in Fig. 7b-d.…”