Graphene-templated synthesis of sandwich-like porous carbon nanosheets for efficient oxygen reduction reaction in both alkaline and acidic media

Abstract

Developing low-cost, high-performance electrocatalysts for the oxygen reduction reaction (ORR) is crucial for implementation of fuel cells and metal-air batteries into practical applications. Graphene-based catalysts have been extensively investigated for ORR in alkaline electrolytes. However, their performance in acidic electrolytes still requires further improvement compared to the Pt/C catalyst. Here we report a self-templating approach to prepare graphene-based sandwich-like porous carbon nanosheets for efficient ORR in both alkaline and acidic electrolytes. Graphene oxides were first used to adsorb m-phenylenediamine molecules which can form a nitrogen-rich polymer network after oxidative polymerization. Then iron (Fe) salt was introduced into the polymer network and transformed into ORR active Fe-N-C sites along with Fe, FeS, and FeN 0.05 nanoparticles after pyrolysis, generating ORR active sandwich-like carbon nanosheets. Due to the presence of multiple ORR active sites. The as-obtained catalyst exhibited prominent ORR activity with a half-wave potential~30 mV more positive than Pt/C in 0.1 mol L −1 KOH, while the half-wave potential of the catalyst was only~40 mV lower than that of commercial Pt/C in 0.1 mol L −1 HClO 4 . The unique planar sandwich-like structure could expose abundant active sites for ORR. Meanwhile, the graphene layer and porous structure could simultaneously enhance electrical conductivity and facilitate mass transport. The prominent electrocatalytic activity and durability in both alkaline and acidic electrolytes indicate that these carbon nanosheets hold great potential as alternatives to precious metalbased catalysts, as demonstrated in zinc-air batteries and proton exchange membrane fuel cells.

Three‐dimensional Polypyrrole Derived N‐doped Carbon Nanotube Aerogel as a High‐performance Metal‐free Catalyst for Oxygen Reduction Reaction

“…The O 1s peak can be deconvoluted into three peaks of the O−C (O 1 ) at the BE of 531.5 eV, the O=C (O 2 ) at 532.6 eV and the O−C=O at 533.8 eV (C−O; O 3 ), respectively. As shown in Figure S2 (a–d), the S 2p peak can be fitted into three peaks of the S 1 and S 2 for −C−S−C− at the BE of 163.9 and 165.0 eV, and the S 3 for −C−SO 2 −C− at the BE of 168.0 eV . Previous studies have shown that the −C−S−C− group may increase the ORR activity .…”

“…As shown in Figure S2 (a–d), the S 2p peak can be fitted into three peaks of the S 1 and S 2 for −C−S−C− at the BE of 163.9 and 165.0 eV, and the S 3 for −C−SO 2 −C− at the BE of 168.0 eV . Previous studies have shown that the −C−S−C− group may increase the ORR activity . The contents of S element in PPy/C‐500, PPy/C‐700, PPy/C‐900 and PPy/C‐1050 are respectively 0.20, 0.16, 0.21 and 0.17 at%, which are rather low and change little with the annealing temperature.…”

“…[31] Previous studies have shown that the À CÀ SÀ CÀ group may increase the ORR activity. [31][32] The contents of S element in PPy/C-500, PPy/C-700, PPy/C-900 and PPy/C-1050 are respectively 0.20, 0.16, 0.21 and 0.17 at%, which are rather low and change little with the annealing temperature. Therefore, the S element may have little effect on catalytic activity of the carbon catalysts pyrolyzed at different temperatures in this study.…”

Controllable synthesis of two-dimensional tungsten nitride nanosheets as electrocatalysts for oxygen reduction reaction

“…Oxygen reduction reaction (ORR) catalysts for the cathodic reaction of DMFCs have been extensively investigated to replace platinum-containing groups, with the aim of enhancing the catalytic activity of ORR while reducing the cost [4,5]. A number of alternative ORR catalysts including non-precious metal (NPM), metal composites, and metal-free composites have been recently considered as potential substitutes for platinum-containing groups catalysts.…”

Fe/Co-based nanoparticles encapsulated in heteroatom-doped carbon electrocatalysts for oxygen reduction reaction

“…Metal-based nanoparticles (NPs) were often generated by an annealing process [19][20][21][22][23], and significant progress in metal-based NPs encapsulated within heteroatomdoped carbon catalysts for ORR has been reported [24]. During the annealing process, metal or other heteroatoms were doped into carbon matrix, and metal-based NPs were encapsulated by heteroatom-doped carbon layers.…”