Herein, we report a "shape fixing via salt recrystallization" method to efficiently synthesize nitrogen-doped carbon material with a large number of active sites exposed to the three-phase zones, for use as an ORR catalyst. Self-assembled polyaniline with a 3D network structure was fixed and fully sealed inside NaCl via recrystallization of NaCl solution. During pyrolysis, the NaCl crystal functions as a fully sealed nanoreactor, which facilitates nitrogen incorporation and graphitization. The gasification in such a closed nanoreactor creates a large number of pores in the resultant samples. The 3D network structure, which is conducive to mass transport and high utilization of active sites, was found to have been accurately transferred to the final N-doped carbon materials, after dissolution of the NaCl. Use of the invented cathode catalyst in a proton exchange membrane fuel cell produces a peak power of 600 mW cm(-2), making this among the best nonprecious metal catalysts for the ORR reported so far. Furthermore, N-doped carbon materials with a nanotube or nanoshell morphology can be realized by the invented method.
Recent advances in the electrical conductivity, intrinsic activity and morphology design of transition-metal-oxide-based oxygen reduction catalysts are summarized.
In this work, an inexpensive electrocatalyst, Ni-doped Mo 2 C nanowires have been directly grown on Ni Foam via a hydrothermal reaction combined with carburization process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and linear scanning 10 voltammetry (LSV) were used to scrutinize the catalysts and the electrochemical performance. The results show that the designed NiMo 2 C/NF catalyst displays enhanced catalytic activity toward hydrogen production with a low onset overpotential of 21 mV. For driving a cathodic current density of 100 mA cm -2 , it only needs overpotential of 150 mV. Such excellent performance of the NiMo 2 C/NF could be ascribed to the high intrinsic activity from a synergistic function of Ni and Mo 2 C, as well as the exposure of more Ni-doped Mo 2 C sites provided by the high aspect ratio of one-dimensional (1D) structure and rich surface area. 15
The sluggish kinetics of the oxygen evolution reaction (OER) is the bottleneck of water electrolysis for hydrogen generation. Developing cost-effective OER materials with a high value of practical application is a prerequisite to achieve extreme performance in both activity and stability. Herein, we report a "dual ligand synergistic modulation" strategy to accurately tune the structure of transition-metal materials at atomic level, which finally achieves satisfactory results for the unity between robust stability and high activity. Remarkably, the elaborately designed S and OH dual-ligand NiCo 2 (SOH) x catalyst exhibits an excellent OER activity with a very small overpotential of 0.29 V at a current density of 10 mA cm −2 and a strong durability even after 30 h accelerated aging at a large current density of 100 mA cm −2 , both of which are superior to most of the state-of-the-art OER catalysts so far. The density functional theory (DFT) calculations disclose that the synergy of OH and S ligands on the surface of NiCo 2 (SOH) x can delicately tune the electronic structure of metal active centers and their chemical environment, which results in optimal binding energies of the OER intermediates (*OH, *O, and *OOH) and a strengthened binding energy between metal and anion ligands, thus leading to an excellent intrinsically enhanced OER activity and stability, respectively. Meanwhile, the special nonmagnetism of NiCo 2 (SOH) x can significantly weaken the resistance of O 2 desorption on the catalyst surface, thus facilitating the O 2 evolution proceedings.
A space-confined interfacial conversion approach is developed to directly transform 3 nm solid Pt nanoparticles into a 5 nm hollow PtFe alloy featuring a Pt-skin surface. The approach presented for the structural evolution from solid Pt NPs to hollow PtFe alloy with controlled size, structure, and composition can be applied to other multimetallic electrocatalysts.
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