Manganese Oxide/Iron Carbide Encapsulated in Nitrogen and Boron Codoped Carbon Nanowire Networks as Accelerated Alkaline Hydrogen Evolution and Oxygen Reduction Bifunctional Electrocatalysts

Abstract

Along with the widespread applications of various energy storage and conversion devices, the prices of precious metal platinum (Pt) and transition-metal cobalt/nickel keep continuously growing. In the future, designing high-efficiency nonprecious-metal catalysts based on low-cost iron (Fe) and manganese (Mn) metals for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is fairly critical for commercial applications of hydrogen fuel cells. In this study, for the first time, we design novel three-dimensional (3D) hybrid networks consisting of manganese oxide (MnO)-modified, iron carbide (Fe3C)-embedded, and boron (B)/nitrogen (N) codoped hierarchically porous carbon nanofibers (denoted FeMn@BNPCFs). After optimizing the pyrolysis temperatures, the optimal FeMn@BNPCFs-900 catalyst displays the best HER and ORR catalytic activities in an alkaline solution. As expected, the HER onset potential (E onset) and the potential at a current density of −10 mA cm–2 for FeMn@BNPCFs-900 in 1.0 M KOH are just 36 and 194 mV more negative than the state-of-the-art 20 wt % Pt/C catalyst with more superior stability. In particular, the FeMn@BNPCFs-900 catalyst shows excellent ORR catalytic activity with a more positive E onset (0.946 V vs RHE), a more positive half-wave potential (E 1/2 = 0.868 V vs RHE), better long-term stability, and higher methanol tolerance surpassing the commercial 20 wt % Pt/C (E onset = 0.943 V vs RHE, E 1/2 = 0.854 V vs RHE) and most previously reported precious-metal-free catalysts in 0.1 M KOH. The synergistic effects of 3D hierarchically macro-/mesoporous architectures, advanced charge transport capacity, abundant carbon defects/edges, abundant B (2.3 atom %) and N (4.9 atom %) dopants, uniformly dispersed Fe3C@BNC NPs, and MnO nanocrystallines are responsible for the excellent HER/ORR catalytic activities of the FeMn@BNPCFs-900 catalyst.

Construction of a Co/MnO Mott–Schottky Heterostructure to Achieve Interfacial Synergy in the Oxygen Reduction Reaction for Aluminum–Air Batteries

“…The high-resolution TEM (HRTEM) image of the nanoparticle taken near the carbon layer (inset of Figure 2b) demonstrates lattice fringes in two different directions with lattice spacings of 0.208 and 0.229 nm, which correspond to Co(111) and MnO(200), respectively. 32,33 These two phases are in close and direct contact without carbon layers or any other secondary phase in between, indicating that a nanoscale heterointerface between Co and MnO phases is formed near the surface of the composite nanoparticle. The formed heterostructure is expected to be beneficial for the realization of interfacial synergy in the Co/MnO heterostructural electrocatalyst.…”

Synthesis of hierarchically structured Fe3C/CNTs composites in a FeNC matrix for use as efficient ORR electrocatalysts

“…In addition, the Fe 3 C particles wrapped in carbon layers enhanced the electronic structure and activity of the active site, which promoted the activity at the Fe(II) sites and resulted in a high ORR activity. 15,[43][44][45]…”

Ni nanoparticles assembled on the surface of biomass-derived porous carbon as competitive candidates for the hydrogen evolution reaction

“…Recently, with the rapid consumption of fossil fuels and severe environmental pollution problems, it is imperative to develop sustainable clean energies, such as wind energy, solar energy, hydrogen energy, geothermal energy, and advanced energy storage technologies. [1][2][3][4][5][6] Among various clean energies, hydrogen is considered as the most promising energy, which is a substitute to fossil fuels when facing alleviating global warming and associated environmental distress. [7][8][9] Besides, the pollution-free energy sources are increasingly being paid attention to by researchers by referring to the trend of sustainable development and ecological protection.…”