Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

Abstract

Developments of high-performance cost-effective electrocatalyts that can replace Pt catalysts have been a central theme in polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). In this direction, nitrogen-doped carbon nanostructures free of metallic components have attracted particular attention. Here we show that directing graphitic carbon nitride frameworks into mesoporous architecture can generate a highly promising metal-free electrocatalyst for an oxygen reduction reaction (ORR) in an acidic medium. The ordered mesoporous carbon nitride (OMCN) was synthesized with a nanocasting strategy using ordered mesoporous silica as a template. A variety of characterizations revealed that the OMCN is constructed with graphitic carbon nitride frameworks and ordered arrays of uniform mesopores. The OMCN showed significantly enhanced electrocatalytic activity for ORR compared to bulk carbon nitride and ordered mesoporous carbon in terms of the current density and onset potential. A high surface area and an increased density of catalytically active nitrogen groups in the OMCN appear to contribute concomitantly to the enhanced performance of the OMCN. Furthermore, the OMCN exhibited superior durability and methanol tolerance to a Pt/C catalyst, suggesting its widespread utilization as an electrocatalyst for PEMFCs and DMFCs.

Effect of visible light and electrode wetting on the capacitive performance of S- and N-doped nanoporous carbons: Importance of surface chemistry

“…That peak is especially visible for the C-B and C-BO carbon samples after wetting in sulfuric acid. The presence of this peak is linked to the oxygen reduction reaction [40,41]. KOH [46] have been reported.…”

“…As seen, VL irradiation visibly increases the cathodic current measured. Since this effect was not observed in the absence of oxygen, we link it to oxygen reduction process on the surface of our electrodes [40,41]. The comparison of the photocurrent densities generated on our polymer-derived carbon electrodes after wetting in water and sulfuric acid are presented in Figure 11.…”

Origin and Perspectives of the Photochemical Activity of Nanoporous Carbons

“…The latter visibly increased the cathodic current measured 131. Since this effect was not observed in the absence of oxygen, it was linked it to oxygen reduction process on the surface of the electrodes 146, 147. After wetting in water, the order of a decreasing photocurrent was C–A > C–B > C–AO = C–BO and sulfuric acid wetting changed the order to C–B > C–AO = C–BO > C–A.…”

Carbon Nanotubes/Heteroatom‐Doped Carbon Core–Sheath Nanostructures as Highly Active, Metal‐Free Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells

“…[3][4][5][6] Among such classes of catalysts, nanocarbons doped with heteroatoms have shown highly promising ORR activity, particularly in alkaline media. [6] Over the last few years, various carbon nanostructures, including carbon nanotubes, [7,8] graphene, [9,10] nanoporous carbons, [11] and carbon nitrides, [12] that were doped with various heteroatoms have been exploited as electrocatalysts for the ORR in alkaline media. Despite this rapid progress, there still remains a multitude of challenges in the development of doped nanocarbon-based electrocatalysts.…”