Shape Control of Mn₃O₄ Nanoparticles on Nitrogen‐Doped Graphene for Enhanced Oxygen Reduction Activity

Abstract

Three kinds of Mn3O4 nanoparticles with different shapes (spheres, cubes, and ellipsoids) are selectively grown on nitrogen‐doped graphene sheets through a two‐step liquid‐phase procedure. These non‐precious hybrid materials display an excellent ORR activity and good durability. The mesoporous microstructure, nitrogen doping, and strong bonding between metal species and doped graphene are found to facilitate the ORR catalytic process. Among these three kinds of Mn3O4 particles, the ellipsoidal particles on nitrogen‐doped graphene exhibit the highest ORR activity with a more positive onset‐potential of –0.13 V (close to that of Pt/C, –0.09 V) and a higher kinetic limiting current density (JK) of 11.69 mA cm–2 at –0.60 V. It is found that the ORR performance of hybrid materials can be correlated to the shape of Mn3O4 nanocrystals, and specifically to the exposed crystalline facets associated with a given shape. The shape dependence of Mn3O4 nanoparticles integrated with nitrogen‐doped graphene on the ORR performance, reported here for the first time, may advance the development of fuel cells and metal‐air batteries.

Mn3O4@CoMn2O4–CoxOyNanoparticles: Partial Cation Exchange Synthesis and Electrocatalytic Properties toward the Oxygen Reduction and Evolution Reactions

“…(7)(8)(9)(10)(11)(12)(13)(14) Among transition metal oxides, Mn-based oxides and particularly spinels have shown outstanding performance for ORR and, to a minor extent, for OER. (7,(15)(16)(17)(18)(19)(20)(21) Besides, Co-based oxides are excellent electrocatalysts for OER, (22)(23)(24)(25) However, the multiple valence and related structural variability of transition metal oxides, which is at the origin of their exceptional electrocatalytic performance, is also behind the difficulty to produce these compounds in a reproducible and controlled manner. This is a particularly important limitation when taking into account the strong dependence of the physicochemical properties of transition metal oxides on composition, structural parameters, and distribution and oxidation state of cations.…”

Effects of surface stability on the morphological transformation of metals and metal oxides as investigated by first-principles calculations

“…The synthesis of highly active facets has been considered as an important procedure to significantly promote the catalytic activity of noble metals, metal oxides, and semiconductors [43][44][45][46]. In particular, the peculiar particle morphological structures of metals and their oxides, such as cube, flower-like, octahedron, and rod, have attracted wide attention in the field of electrochemical device applications [47][48][49]. The basis of this strategy is that the surface atomic configuration and coordination control the reactivity and can be finely tuned by morphological control [50,51].…”

In situ anchoring of Co9S8 nanoparticles on N and S co-doped porous carbon tube as bifunctional oxygen electrocatalysts

“…In principle, in situ anchoring of active TMC NPs on heteroatom-doped porous carbons can be a good solution to this problem due to their high electron conductivity, porous structure for high flux of mass transportation and the extra active sites induced by heteroatom doping. 1,[18][19][20] Furthermore, the possible synergistic effects between TMC NPs and heteroatom-doped porous carbon may be collected to markedly enhance the OER and ORR performance. Therefore, it is highly important to explore the hybrids of TMCs and heteroatom-doped carbons towards novel bifunctional catalysts for both the OER and ORR.…”