Imidazolatic-Framework Bimetal Electrocatalysts with a Mixed-Valence Surface Anchored on an rGO Matrix for Oxygen Reduction, Water Splitting, and Dye Degradation

Abstract

This paper presents a simple strategy for manufacturing bifunctional electrocatalystsgraphene nanosheets (GNS) coated with an ultrafine NiCo-MOF as nanocomposites (denoted NiCo-MOF@GNS) having a N-doped defect-rich and abundant cavity structure through one-pool treatment of metal− organic frameworks (MOFs). The precursors included N-doped dodecahedron-like graphene nanosheets (GNS), in which the NiCo-MOF was encompassed within the inner cavities of the GNS (NiCo-MOF@GNS) at the end or middle portion of the tubular furnace with several graphene layers. Volatile imidazolate N x species were trapped by the NiCo-MOF nanosheets during the pyrolysis process, simultaneously inserting N atoms into the carbon matrix to achieve the defect-rich porous nanosheets and the abundantly porous cavity structure. With high durability, the asprepared nanomaterials displayed simultaneously improved performance in the oxygen reduction reaction (ORR), the oxygen evolution reaction (OER), and photocatalysis. In particular, our material NiCo-MOF@GNS-700 exhibited excellent electrocatalytic activity, including a half-wave potential of 0.83 V (E ORR, 1/2 ), a low operating voltage of 1.53 V (E OER, 10 ) at 10 mA cm −2 , a potential difference (ΔE) of 1.02 V between E OER, 10 and E ORR, 1/2 in 0.1 M KOH, and a low band gap of 2.61 eV. This remarkable behavior was due to the structure of the defect-rich porous carbon nanosheets and the synergistic impact of the NPs in the NiCo-MOF, the N-doped carbon, and NiCo-N x . Furthermore, the hollow structure enhanced the conductivity and stability. This useful archetypal template allows the construction of effective and stable bifunctional electrocatalysts, with potential for practical viability for energy conversion and storage.

One-Step Electrodeposition of a Mesoporous Ni/Co-Imidazole-Based Bimetal-Organic Framework on Pyramid-like NiSb with Abundant Coupling Interfaces as an Ultra-Stable Heterostructural Electrocatalyst for Water Splitting

“…46 On the other hand, the NiCo-MOF surrounding the NiSb layers had distinct lattice fringes with a d-spacing of 0.215 nm, which is well indexed to the (111) plane of this MOF. 47 In Figure 3f, the selected area electron diffraction (SAED) patterns revealed the presence of the welldefined diffraction circles, corresponding to the (111), (220), and (311) planes, implying that the NiCo-MOF was a polycrystalline. 47,48 Taken together, obtained results support the successful formation of the MOF structures on the NiSb layer.…”

“…By comparing the XPS spectra of Ni and Co in monometallic Ni-MOF@NiSb and Co-MOF@NiSb with those of bimetallic NiCo-MOF@NiSb, it can be seen that the characteristic peaks of NiCo-MOF@NiSb have shifted toward less binding energy, which is possibly due to the changes in the coordination environment between Hmim ligands and metal centers after the introduction of second metal ion, leading to alteration in the local electronic structure to an electron-rich state by the metal sites. , As an outcome, the synergistic effect of mixed metals redistributes atomic charge between Ni and Co centers in the MOF structure, modulating the adsorption/desorption of reaction intermediates during the HER and OER reactions. , …”

Aerosol‐assisted synthesis of bimetallic nanoparticle‐loaded bamboo‐like N‐doped carbon nanotubes as an efficient bifunctional oxygen catalyst for Zn‐air batteries

“…However, although it was observed in some cases in RDE experiments in same measurement conditions, this phenomenon was rarely investigated in detail so far in the literature. [37][38][39][40] The presence of an obvious reduction peak may be attributed to the reduction of the O 2 adsorbed on the surface of catalyst, which coincides with the reduction of O 2 diffused in the electrolyte bulk. The presence of reduction peaks was relevant to non-steady-state phenomena originated from experimental condition in which potential varied linearly in time.…”

Ultrathin Two-Dimensional Bimetal–Organic Framework Nanosheets as High-Performance Electrocatalysts for Benzyl Alcohol Oxidation

“…In terms of electrocatalytic performance, the current density of NiCo-61-MOF/NF was as high as 338.16 mA cm −2 , which was the best compared to those of Ni-MOF/NF (298.84 mA cm −2 ) and NiCo-21-MOF/NF (295.48 mA cm −2 ) (Figure 3c). 40 When compared with the previous reports in Table S2, 25,28,29,41−47 it was clear that the Ni-based electrocatalysts presented efficient EBO performance. The NiCo-61-MOF nanosheets demonstrated a comparable and even superior electrocatalytic performance compared to the previous reports under a similar condition.…”

“…The onset potentials of NiCo-61-MOF/NF and NiCo-21-MOF/NF were around 1.25 V (vs RHE) lower than that of Ni-MOF/NF (1.34 V vs RHE). In terms of electrocatalytic performance, the current density of NiCo-61-MOF/NF was as high as 338.16 mA cm –2 , which was the best compared to those of Ni-MOF/NF (298.84 mA cm –2 ) and NiCo-21-MOF/NF (295.48 mA cm –2 ) (Figure c) . When compared with the previous reports in Table S2, ,,,− it was clear that the Ni-based electrocatalysts presented efficient EBO performance.…”