Influence of Nitrogen Doping on Oxygen Reduction Electrocatalysis at Carbon Nanofiber Electrodes

Abstract

Nondoped and nitrogen-doped (N-doped) carbon nanofiber (CNF) electrodes were prepared via a floating catalyst chemical vapor deposition (CVD) method using precursors consisting of ferrocene and either xylene or pyridine to control the nitrogen content. Structural and compositional differences between the nondoped and N-doped varieties were assessed using TEM, BET, Raman, TGA, and XPS. Electrochemical methods were used to study the influence of nitrogen doping on the oxygen reduction reaction (ORR). The N-doped CNF electrodes demonstrate significant catalytic activity toward oxygen reduction in aqueous KNO(3) solutions at neutral to basic pH. Electrochemical data are presented which indicate that the ORR proceeds by the peroxide pathway via two successive two-electron reductions. However, for N-doped CNF electrodes, the reduction process can be treated as a catalytic regenerative process where the intermediate hydroperoxide (HO(2)(-)) is chemically decomposed to regenerate oxygen, 2HO(2)(-) <==> O(2) + 2OH(-). The proposed electrocatalysis mechanisms for ORR at both nondoped and N-doped varieties are supported by electrochemical simulations and by measured difference in hydroperoxide decomposition rate constants. Remarkably, approximately 100 fold enhancement for hydroperoxide decomposition is observed for N-doped CNFs, with rates comparable to the best known peroxide decomposition catalysts. Collectively the data indicate that exposed edge plane defects and nitrogen doping are important factors for influencing adsorption of reactive intermediates (i.e., superoxide, hydroperoxide) and for enhancing electrocatalysis for the ORR at nanostructured carbon electrodes.

Successful functionalization of superporous zeolite templated carbon using aminobenzene acids and electrochemical methods

“…It is known that the generation of nitrogen surface groups is of high interest due to the number of applications that are available for nitrogen-doped carbon materials. Among others, they are of interest for increasing the electrochemical activity of carbon materials in the oxygen reduction reaction [7], [8]; for increasing the capacitance, rate performance and durability as electrodes of supercapacitors [9]- [11]; for enhancement of gas and liquid adsorption of acid adsorbates [12]; for the preparation of novel heterogeneous catalysts [13], [14] and for the immobilization of bio-molecules [15]. The synthesis of Ncontaining ZTC is done using chemical vapor deposition during its synthesis with which Nspecies are incorporated in the carbon network [16]- [20]; however, it is not possible to control the type of N-species and it inevitably becomes diverse.…”

Highly efficient cathode catalyst layer based on nitrogen-doped carbon nanotubes for the alkaline direct methanol fuel cell

“…Recently, nitrogen-modified carbon materials have been shown to have inherent oxygen reduction activity that can reach or even exceed the activity of Pt-catalysts, while being immune to CO and methanol poisoning, and catalyst nanoparticle agglomeration [10][11][12]. These catalysts show moderate activity towards oxygen reaction in acidic and neutral conditions, and excellent activity in alkaline conditions [13][14][15][16][17].…”

“…graphene [10,[23][24][25][26][27][28][29][30][31][32][33], carbon nanotubes [11,20,21,[34][35][36][37][38][39][40][41][42][43], carbon nanofibers [12,[44][45][46][47], mesoporous carbon [15,22], graphitic carbon [48,49], carbon spheres [19,[50][51][52][53], carbon nanocages 4 [54], flower-like carbon [55], carbon aerogel [56,57], vesicular carbon [58], nanodiamonds [59]) relatively few have been tested in actual fuel cell conditions [58,[60][61][62]…”

Nanocarbon-based electrochemical systems for sensing, electrocatalysis, and energy storage

“…[111] A 9 strong correlation between the ORR peak potential and the nitrogen doping level was also observed; ORR peaks 10 shifted about +30 mV per 1 atom% nitrogen incorporated.…”

“…CNFs provide easier electron transfer along the continuous conductive fibers than do disconnected 6 carbon systems (e.g., carbon particles) where the interfacial resistances between the individual carbon entities exception is nitrogen-doped CNFs. [111] Examples of utilizing carbon nanomaterials for the development of elec-…”