Ni/Fe-based
bimetallic nanoarchitecture materials play an important
role in the development of non-precious-metal-based electrocatalysts
toward water splitting, but the low activity and poor stability greatly
hinder their commercial applications. It is significant to explore
facile and effective methods to improve their electrocatalytic activity.
A simple self-template strategy is demonstrated to fabricate a hollow
bipyramid constructed by P-doped FeNi alloys/NiFe2O4 nanoparticles encapsulated in carbon network (P-Ni0.5Fe@C). Bimetallic analogous MIL-101 (Fe) precursor (Ni0.5Fe-BDC CP) with uniform morphology and stable structure was synthesized
through a solvothermal reaction. By subsequent carbonization and phosphorization
steps, P element was doped into the composite FeNi alloys/NiFe2O4 nanoparticles. Benefiting from the efficient
mass and electron transfer of the hollow structure, the precise adjustment
for the electron structure of P dopants, and carbon-encapsulated active
components that could provide large numbers of active sites as well
as prevent the aggregation and dissolution of active components, the
optimal P-Ni0.5Fe@C catalyst exhibits a low overpotential
of 256 mV to reach a current density of 10 mA cm–2, a small Tafel slope of 65 mV dec–1, and remarkable
long-term stability toward oxygen evolution reaction in 1 M KOH, which
is better than that of commercial IrO2 (318 mV at 10 mA
cm–2 for overpotential and 120 mV dec–1 for Tafel slope, respectively). More remarkably, when it was employed
in a two-electrode configuration based on P-Ni0.5Fe@C as
anode and commercial Pt/C as cathode catalysts (P-Ni0.5Fe@C || Pt/C), a potential of only 1.49 V (corresponding overpotential
of 260 mV) was required to achieve 10 mA·cm–2. This work provides insight into the rational composition and morphology
design of an earth-abundant electrocatalyst with highly efficient
electrocatalytic activities toward overall water splitting.
NiFe0.1O with grain boundary defects possesses a smaller ECSA (Cdl = 3.23 mF cm−2) than other samples. However, NiFe0.1O shows the highest electrocatalytic OER performance.
Metal–organic frameworks (MOFs), as precursors for synthesizing new carbon materials, hold promise for applications in the oxygen reduction reaction (ORR).
A set of novel catalysts FeMn/N‐CNTs that partly maintain the core‐shell structure have been prepared successfully by calcination of analogous MOF‐74, which has bimetallic species (Fe and Mn) and a cheap organic ligand (2, 5‐dihydroxylbenzoic acid, DHBA) with melamine as additional nitrogen source. These catalysts exhibit a distinctive microstructure of Fe−Mn alloys surrounded by N‐doped carbon nanotubes (CNTs). Electrochemical methods have been employed to investigate their activity in oxygen reduction reaction (ORR) in alkaline solution. The highest ORR performance of Fe3Mn1/N‐CNTs‐100 shows that the half wave potential is at 0.865 V and the kinetic current density (at 0.9 V) is 1.447 mA cm−2, which are higher than those of commercial Pt/C (0.855 V, 0.946 mA cm−2). In addition, Fe3Mn1/N‐CNTs‐100 is much more durable than commercial Pt/C under the conditions tested. The highly efficient ORR performance may be attributed to the unique microstructure and large surface area with appropriate pore size, as well as to the synergistic effects between the pyridinic N species and the Fe−Nx species that play important roles in ORR in alkaline solution. However, in acid medium, only Fe−Nx species catalyze ORR and pyridinic N species are limited to work as the active sites. This study may prompt others to explore the development of heteroatom‐doped CNTs surrounding particles as efficient catalyst for ORR and fuel cell applications.
Catalysts applied for oxygen evolution reaction (OER) are vital to bring future renewable energy systems and convert the water to oxygen and hydrogen fuel. Herein, we report that bimetal-glycerate hollow spheres organized by nanosheets (CoFeG-HS) can be first produced by the one-pot template-free method as an efficient OER electrocatalyst. According to the time-dependent experiments, the growing mechanism gets revealed, assigned to the Ostwald ripening process. Compared with the samples after they are annealed, the catalyst of CoFeG-HS shows greatly lower overpotential and enhanced kinetics for OER, with an overpotential of 242 mV at 10 mA•cm −2 , and a Tafel slope of 49.4 mV•dec −1 because of the richness of oxyhydroxidecontaining species on the surface of catalysts is helpful to the high performance of the OER. Based on the comparison with the Co-glycerate and Fe-glycerate, the CoFeG-HS with more highly active performance and cycled stability profits from the specific hollow structure, optimized composition on the surface, and interaction of Co 2+ and Fe 3+ . The experiment of the catalyst with/without black carbon shows that the important role of black carbon is in reducing the electron transfer resistance to improve the activity. Thus, the currently developed CoFeG-HS with superior OER performance may potentially serve as a material for use in industrial alkaline water electrolyzers.
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