Facile Single-Step Synthesis of Nitrogen-Doped Reduced Graphene Oxide-Mn₃O₄ Hybrid Functional Material for the Electrocatalytic Reduction of Oxygen

Abstract

Development of efficient electrocatalyst based on non-precious metal that favors the four-electron pathway for the reduction of oxygen in alkaline fuel cell is a challenging task. Herein, we demonstrate a new facile route for the synthesis of hybrid functional electrocatalyst based on nitrogen-doped reduced graphene oxide (N-rGO) and Mn3O4 with pronounced electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline solution. The synthesis involves one-step in situ reduction of both graphene oxide (GO) and Mn(VII), growth of Mn3O4 nanocrystals and nitrogen doping onto the carbon framework using a single reducing agent, hydrazine. The X-ray photoelectron (XPS), Raman and FTIR spectral, and X-ray diffraction measurements confirm the reduction of GO and growth of nanosized Mn3O4. The XPS profile reveals that N-rGO has pyridinic (40%), pyrrolic (53%), and pyridine N oxide (7%) types of nitrogen. The Mn3O4 nanoparticles are single crystalline and randomly distributed over the wrinkled N-rGO sheets. The hybrid material has excellent ORR activity and it favors the 4-electron pathway for the reduction of oxygen. The electrocatalytic performance of the hybrid catalyst is superior to the N-rGO, free Mn3O4 and their physical mixture. The hybrid material shows an onset potential of -0.075 V, which is 60-225 mV less negative than that of the other catalyst tested. It has excellent methanol tolerance and high durability. The catalytic current density achieved with the hybrid material at 0.1 mg cm(-2) is almost equivalent to that of the commercial Pt/C (10%). The synergistic effect of N-rGO and Mn3O4 enhances the overall performance of the hybrid catalyst. The nitrogen in N-rGO is considered to be at the interface to bridge the rGO framework and Mn3O4 nanoparticles and facilitates the electron transfer.

Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

“…39,85 The reported facile single-step synthesis of a nitrogen-doped reduced graphene oxide-Mn 3 O 4 hybrid was characterized by XPS. 65 As seen from Fig. 9b, the deconvoluted analysis of N 1s at binding energies from 396 to 404 eV, suggests the desirable doping of N to graphene.…”

“…Bag and co-workers 65 successfully synthesized nitrogendoped reduced graphene oxide (N-rGO) and Mn 3 O 4 hybrid (Mn 3 O 4 /N-rGO) by the one-step in situ reduction of both graphene oxide (GO) and Mn 7+ by hydrazine (Fig. 6a), and the resulting functional electrocatalysts exhibit pronounced electrocatalytic activity towards ORR in alkaline solution.…”

“…In particular, the graphene-based transition metal oxide nanocomposites show outstanding ORR performance in saving cost, thus further decreasing the onset and half-wave potentials, elevating the durability and methanol tolerance. 43,47,48,[50][51][52]55,59,65,66,68,69,74,114,131,132 Iron containing nanoparticles on graphene catalysts have been found to be a group of promising non-noble metal nanocatalysts for the ORR. In a recent work, 43 three-dimensional N-doped graphene aerogel-supported Fe 3 O 4 nanoparticles (Fe 3 O 4 /N-GAs) were synthesized for the efficient catalysis of the ORR.…”

“…However, slight differences of ORR activity of the above catalysts depended strongly on the crystallographic structures with the order of α-> β-> γ-MnO 2 . 63,140 In addition, Bag et al 65 …”

Synthesis of Porous Ni–Co–Mn Oxide Nanoneedles and the Temperature Dependence of Their Pseudocapacitive Behavior

“…and Mn 3+ is difficult (Bag et al, 2014). Based on these analyses, the surface of as-prepared Ni-Co-Mn oxide possesses a composition containing Ni 2+ , Ni 3+ , Co 2+ , Co 3+ , Mn 2+ , and Mn 3+ .…”