N‐doped oxygen vacancy‐rich NiCo ₂ O ₄ nanoarrays for supercapacitor and non‐enzymatic glucose sensing

Abstract

Summary Battery‐type transition metal oxides (TMOs) gained great attention as an electrode in a supercapacitor (SC) owing to their high electrochemical activity, however, the performance of SCs influenced by low intrinsic conductivity and lower cycling stability. To address the issues, we propose an effective strategy of nitrogen doping and increasing the oxygen vacancies of hydrothermally synthesized nickel‐cobalt oxide (N‐Ov/NiCo2O4‐350) nanowire arrays. The modified electrode has a variable superficial nanoporous architecture and a favorable electronic structure resulting in a greatly increased specific surface area and a suitable electron/ion diffusion network. The synthesized hybrid electrode exhibited a specific capacity of 256 mAh g−1 and a high energy density of 83.18 Wh kg−1 at 203.1 W kg−1. Likewise, a non‐enzymatic glucose sensor with N‐Ov/NiCo2O4‐350 achieved a broad linear detection range of 0–555 mM, an ultra‐high sensitivity of 29 811.53 μA·mM−1·cm−2, a short response time of approximately 2.2 s, and a low detection limit of 0.02 μM (S/N = 3). The superior electrochemical and glucose‐sensing capabilities of the N‐Ov/NiCo2O4‐350 hybrid nanostructure demonstrated the potential of the electrode.

Highly sensitive detection of glucose at a novel non‐enzyme electrochemical sensing based on Mo‐doped CoO Nanosheets

“…This showed that appropriate amount of Mo doping can increase the proportion of oxygen vacancies and the number of available active sites, which will improve the electrochemical reaction rate. [46][47] In Mo 3d spectra (Figure 4d), the peak for Mo 6 + 3d 5/2 and Mo 6 + 3d 3/2 were at 232.26 and 235.37 eV, and the peak positioned at 233.08 eV and 236.26 eV should be attributed to Mo 6 + 3d 5/2 and Mo 6 + 3d 3/2 , in consistent with the vibrational peaks from Raman spectra. Based on the above XPS analysis, it can be concluded that the successful doping of Mo element in MoÀ CoO-1 endowed the material more defects and oxygen vacancy, benefiting the nearby Co(II) convert into Co(IV) during the electrochemical process and enhancing the electrochemical catalytic activity of the prepared material.…”

“…It can be clearly seen that the proportion of oxygen vacancy in Mo−CoO‐1 is 47 %, which is significantly increased compared with 34 % and 40 % of the other two samples. This showed that appropriate amount of Mo doping can increase the proportion of oxygen vacancies and the number of available active sites, which will improve the electrochemical reaction rate [46–47] . In Mo 3d spectra (Figure 4d), the peak for Mo 6+ 3d 5/2 and Mo 6+ 3d 3/2 were at 232.26 and 235.37 eV, and the peak positioned at 233.08 eV and 236.26 eV should be attributed to Mo 6+ 3d 5/2 and Mo 6+ 3d 3/2 , in consistent with the vibrational peaks from Raman spectra.…”

Plasma‐Engineering of Oxygen Vacancies on NiCo2O4 Nanowires with Enhanced Bifunctional Electrocatalytic Performance for Rechargeable Zinc‐air Battery

“…As shown in Figure S16 (Supporting Information), the broad oxidation peak (A 1 ) in the first CV cycle from 1.2 to 1.4 V belongs to the M 2+ /M 3+ (M = Ni and Co) redox couples, and the peak (A 2 ) at ≈1.50 V corre-sponds to the Co 3+ /Co 4+ oxidation process. The whole process is described by the following reactions: [70,71] NiCo…”

“…Previous works have revealed that the Co 2+ and Ni 2+ sites were oxidized to CoOOH and NiOOH as the active sites for oxygen electrocatalysis. [45,[70][71][72][73][74][75] On the other hand, the cathodic sweep from 1.6 to 1.1 V also exhibits a broad peak (C 1 ) at ≈1.44 V and a small peak (C 2 ) at ≈1.18 V, which are identified as the reduction of Co 4+ to Co 3+ and M 3+ to M 2+ , respectively. It is clearly shown in Figure S17 (Supporting Information) that the C 2 peak for M 3+ to M 2+ is negligible, and meanwhile, the A 1 peak for M 2+ to M 3+ in the second and followed CV curves are much lower than that in the first CV curves, suggesting that the pre-oxidation of M 2+ to M 3+ in the first anodic sweep is an irreversible reaction, which provides a stable catalytic surface for the oxygen electrocatalysis.…”

Research Progress on Biomimetic Nanomaterials for Electrochemical Glucose Sensors

“…In addition, spinel are relatively mature nanomaterials developed for biomimetic catalysis of glucose. Seong et al [ 73 ] proposed an effective nitrogen doping strategy to synthesize the oxygen vacancy of Ni-Co oxide (N-Ov/NiCo 2 O 4 -350) nanowire arrays. The modified electrode has obvious nanoporous structure and favorable electronic structure, thus significantly increasing the specific surface area and suitable electron/ion diffusion network.…”