NiCo nanoalloy encapsulated in graphene layers for improving hydrogen storage properties of LiAlH4

Abstract

NiCo nanoalloy (4–6 nm) encapsulated in grapheme layers (NiCo@G) has been prepared by thermolysis of a 3D bimetallic complex CoCo[Ni(EDTA)]2·4H2O and successfully employed as a catalyst to improve the dehydrogenation performances of LiAlH4 by solid ball-milling. NiCo@G presents a superior catalytic effect on the dehydrogenation of LiAlH4. For LiAlH4 doped with 1 wt% NiCo@G (LiAlH4-1 wt% NiCo@G), the onset dehydrogenation temperature of LiAlH4 is as low as 43 °C, which is 109 °C lower than that of pristine LiAlH4. 7.3 wt% of hydrogen can be released from LiAlH4-1 wt% NiCo@G at 150 °C within 60 min. The activation energies of LiAlH4 dehydrogenation are extremely reduced by 1 wt% NiCo@G doping.

Two-dimensional CoNi nanoparticles@S,N-doped carbon composites derived from S,N-containing Co/Ni MOFs for high performance supercapacitors

“…Many studies have demonstrated that the formed carbon structure during pyrolysis of MOFs precursor acts as dual role, namely, reduction reagent to reduce metal ions into active metal phase and conductive support for dispersed metal nanoparticles. 19,22,29 In this study, relatively uniformly dispersed nanoparticles with sizes of 5.0~15 nm can be clearly observed on carbon sheets after pyrolysis treatment of Co/Ni MOFs precursor, exhibiting an average particle size of ~7.9 nm (Fig. 2d).…”

“…Also, we found that the distribution of S element is more obvious located at CoNi nanoparticles, possibly meaning the formation of sectional Co or/and Ni sulfides during pyrolysis of Co/Ni MOFs. This could 22 The actually measured atomic ratio of Co to Ni is 0.89 (slightly lower than 1:1) in CoNi@SNC sample by ICP-OES, possibly meaning partial Ni 2+ substituting Co 2+ in MOFs structure. Except for the diffraction peaks of CoNi alloy, several weaker diffraction peaks at 2θ=29.8, 41.5, 47.4° can be ascribed to the (311) plane of cubic Co9S8 and (010), (011) planes of hexagonal Co, indicating a coexistence of Co9S8, hexagonal Co and CoNi alloy after pyrolysis of Co/Ni MOFs nanosheets.…”

“…2e shows very clear crystalline planes with d-spacings of 0.204 nm and 0.177 nm, which can be ascribed to the (111) and (200) planes of metallic Co and Ni respectively, suggesting the formation of highly crystalline CoNi alloy nanoparticles on carbon sheet structure after pyrolysis treatment of Co/Ni MOFs nanosheets. 22,30,31 Fig. 2f shows the EDX mapping images of Co/Ni MOFs derived carbon material obtained from Fig.…”

“…Incorporation of Co/Ni-based active components into porous carbon structures has been widely adopted to fabricate high performance electrode materials for supercapacitors. 18,19,[22][23][24][25] The advantages of the above approach mentioned are: (1) the formed carbon material concurrently as reduction reagent to in situ reduce Co 2+ /Ni 2+ on carbon structure into metal Co or Ni or CoNi alloy nanoparticles; (2) carbon material with high surface area capable of improving the dispersibility of Co or Ni or CoNi alloy nanoparticles, favourable for the exposure of electrochemical active sites; (3) the formed Co or Ni or CoNi alloy nanoparticles on carbon substrate with enhanced electrical conductivity, favourable for electron transfer; (4) the composite with porous structure to improve redox-related mass transport during electrochemical measurement. These advantages of the fabricated composites collectively contribute high supercapacitor performance when used as electrode materials.…”

Graphitic Carbon‐NiCo Nanostructures as Efficient Non‐Precious‐Metal Electrocatalysts for the Oxygen Reduction Reaction

“…[33] Deconvolution of the N 1s XPS spectrum (Figure 4b) revealed two different kinds of nitrogen atoms: 64 % of pyridinic N (398.6 eV) and 34.8 % of graphitic N (400.8 eV) atoms. Binding energies of 852.7 and 869.6 eV revealed the presence of metallic nickel (Ni 0 ) in the NiCo@GC-600 catalyst; [35] in addition, the two major-intensity peaks having binding energies of 855.1 and 872.5 eV confirmed the presence of oxidized metallic nickel species, arising from surface oxidation; [36] furthermore, strong satellite peaks at 861.3 and 879.6 eV revealed that the majority of the surface nickel was in the higher oxidation state of Ni 2 + . Binding energies of 852.7 and 869.6 eV revealed the presence of metallic nickel (Ni 0 ) in the NiCo@GC-600 catalyst; [35] in addition, the two major-intensity peaks having binding energies of 855.1 and 872.5 eV confirmed the presence of oxidized metallic nickel species, arising from surface oxidation; [36] furthermore, strong satellite peaks at 861.3 and 879.6 eV revealed that the majority of the surface nickel was in the higher oxidation state of Ni 2 + .…”