NiO/nanoporous graphene composites with excellent supercapacitive performance produced by atomic layer deposition

Abstract

Nickel oxide (NiO) is a promising electrode material for supercapacitors because of its low cost and high theoretical specific capacitance of 2573 F g(-1). However, the low electronic conductivity and poor cycling stability of NiO limit its practical applications. To overcome these limitations, an efficient atomic layer deposition (ALD) method is demonstrated here for the fabrication of NiO/nanoporous graphene (NG) composites as electrode materials for supercapacitors. ALD allows uniform deposition of NiO nanoparticles with controlled sizes on the surface of NG, thus offering a novel route to design NiO/NG composites for supercapacitor applications with high surface areas and greatly improved electrical conductivity and cycle stability. Electrochemical measurements reveal that the NiO/NG composites obtained by ALD exhibited excellent specific capacitance of up to ∼ 1005.8 F g(-1) per mass of the composite electrode (the specific capacitance value is up to ∼ 1897.1 F g(-1) based on the active mass of NiO), and stable performance after 1500 cycles. Furthermore, electrochemical performance of the NiO/NG composites is found to strongly depend on the size of NiO nanoparticles.

Conformally deposited NiO on a hierarchical carbon support for high-power and durable asymmetric supercapacitors

“…Excluding the peaks of the carbon substrate, all other diffraction peaks can be well indexed to NiO (JCPDS 65-5745), which match well as previous reports on ALD NiO. 34 XPS survey spectra of the GF-CNT@NiO is presented in Figure 2b-d (the wide range spectra is in Electronic Supplementary Information). The peaks located at 871.5 and 853.0-854.7 eV accompanied by a broad satellite peak correspond to the characteristic Ni 2p 1/2 and Ni 2p 3/2 peaks of Ni 2+ (Figure 2b), 36,37 and the peak of O 1s centered at 530.1 eV and 531.6 eV can be attributed to the metal oxide form (O2 -) and surface -OH group, respectively ( Figure 2c).…”

“…But if the active material of NiO is further increased, the thicker NiO layer can retard the electrochemical reaction at high rate, which can explain the capacity decrease of GF-CNT@900NiO compared with GF-CNT@600NiO. 34,43 In current work, GF-CNT@600NiO shows the optimized capacity. Figure 3c shows the relationship between the capacity of the samples and the charge-discharge current densities.…”

“…Since the amount of deposited NiO can be simply controlled by ALD cycles 32,33 , in present work NiO with 300, 600, and 900 ALD cycles have been deposited on the GF-CNT, noted as GF-CNT@300NiO, GF-CNT@600NiO, and GF-CNT@900NiO, respectively. The growth rate of NiO on CNT is ~ 0.02 nm per cycle, which is a little faster than a similar work of NiO on graphene, 34 and it is comparable to the growth rate of Fe2O3 on CNT. 35 To further study the detailed nanostructure and chemical composition of the GF-CNT@NiO, transmission electron microscopy (TEM) was performed, and the results are shown in Figure 1d-f.…”

“…38 In Figure 2d, the C 1s peak at 284.6 eV illustrates the C-C bond, and the C-O and C=O bonds are also shown by the small peaks at 285.8 and 288.6 eV, respectively. 34 A detailed XPS results on all three samples(GF-CNT@300NiO, GF-CNT@600NiO, and GF-CNT@900NiO) is shown in Figure S3. From the XPS results, we found the Ni 2p spectra from all the three samples are almost the same, but in the C 1s spectra, the GF-CNT@900NiO shows less C-O and C=O bonds than the other two samples, which may result in poorer stability than those of GF-CNT@300NiO and GF-CNT@600NiO.…”

Nickel Oxide/Graphene Composites: Synthesis and Applications

“…Chen et al. achieved a uniform deposition of NiO NPs with controlled sizes on graphene through this method, which provided a specific capacitance of 907 F g −1 and 94 % retention after 1500 cycles . Yu et al.…”