Boron-Doped Trimetallic Cu-Ni-Co Oxide Nanoneedles for Supercapacitor Application

Abstract

Doping has been one of the efficient ways in incorporating potential elements to further increase electrode efficiencies. The introduction of boron as a dopant reinforces transition metal to oxide bonding and makes it stable during the cycling process. Herein, we prepared Cu-Ni-Co oxide (CNCO) with agglomerated nanoneedle-like structures in the first step and then structurally doped it with boron (CNCO-D-SD) in the second step. The agglomerated nanoneedle-like structures with merged tips were retained with boron doping, but stability was decreased. Then, we evaluated the incorporation of boron in one step, and, interestingly, it resulted to self-organized, boron-doped Cu-Ni-Co oxide (CNCO-D-SO) one-dimensional (1D) vertically aligned nanoneedle-like structures. Herein, boric acid acted as a dopant as well as a structural-directing agent. The CNCO-D-SO exhibited superior overall electrochemical performance to the CNCO and CNCO-D-SD. Interestingly, the as-assembled hybrid supercapacitor (HSC) device made from CNCO-D-SO//rGO showed outstanding stability (87% after 8,000 cycles) compared to CNCO-D-SD//rGO (46% after 5,000 cycles) and bare CNCO//rGO (53% after 5,000 cycles). This study demonstrates that doping can improve the stability and/or capacity of Cu-Ni-Co oxide, but the nature of the active materials is also equally important for achieving satisfactory performance. Furthermore, this study suggests a more efficient as well as time-, energy-, and cost-saving preparation of structured electrodes. Overall, the outcomes showed that the as-assembled CNCO-D-SO//rGO HSC device had higher storage capacity, better stability and conductivity, and scalable time-saving fabrication, suggesting that it has great potential in next-generation energy storage applications.

Synergistic integration of three‐dimensional architecture composed of two‐dimensional nanostructure ternary metal oxide for high‐performance hybrid supercapacitors

“…Interestingly, two plateaus of the NCMO electrode are attributed to more abundant active sites arising from ternary metals than others. When current densities increase from 1 to 30 A g −1 , the GCD profiles of NCMO preserve the well‐defined plateau‐like and nearly symmetric profiles (Figure 4D and Figure S5), which is consistent with the reversible Faradic behavior of CVs 27,35,37,46,47 . Figure 4E depicts the plots of the C s values derived from area under the discharge curves varying current densities.…”

“…Noticeably, the D13 HSC delivers maximum ED and PD of 51.22 W h kg −1 and 41.67 kW kg −1 than those of D11 (42.40 W h kg −1 and 37.73 kW kg −1 ), D12 (43.79 W h kg −1 and 39.47 kW kg −1 ), and D14 (48.86 W h kg −1 and 40.94 kW kg −1 ), respectively. The obtained values of D13 are higher than the previously reported data, summarized in Table S2 27‐29,33,42,48 . Furthermore, the long‐term stability was evaluated for the D13 HSC, as shown in Figure 7C.…”

“…As shown in the high‐resolution Ni 2p spectrum in Figure 3C, the observed two prominent peaks of Ni 2p 3/2 and Ni 2p 1/2 with two‐satellite waves (sat. ), which implies the presence of Ni 2+ species 27,32 . Likewise, the high‐resolution Co 2p spectrum exhibits a couple of major peaks of Co 2p 1/2 and Co 2p 3/2 , respectively, along with two shake‐up satellite peaks (sat.)…”

“…The CV curve of the hierarchically structured NCMO microflower at 25 mV s −1 shows two sets of redox couples with a larger current than those of other electrodes (Figure 4A). The existence of typical Faradaic redox reactions in CV shape is associated with M–O/M–O–OH (where M = Ni, Co, or Mo cations) interacting with OH − anions 27,29,30,43 …”

“…Furthermore, the nanostructures of TMOs such as nanoparticles, nanowires, nanorods, nanosheets, nanoflower, microsphere/flower, and core‐shell archistructure can greatly improve the electrochemical performance of HSCs 5,22,28,30‐35 . When the nanostructured materials are assembled into more complex three‐dimensional (3D) structures, the hierarchically structured materials have advantages in terms of their large specific area, fast ion transportation pathway, percolated electronic conduction, and buffering space 27,30,33,35‐38 …”