Ultrathin Metal–Organic Framework Nanosheet-Derived Ultrathin Co₃O₄ Nanomeshes with Robust Oxygen-Evolving Performance and Asymmetric Supercapacitors

Abstract

Ultrathin metal-organic framework (MOF) nanosheets possessing inherent advantages of both two-dimensional (2D) features and MOFs are attracting intensive research interest. The direct manufacture of MOF nanosheets is still a challenge up to now. Here, we have developed a novel bottom-up approach to synthesize zeolitic imidazolate framework-67 (ZIF-67) nanosheets, which can be in situ converted into CoO ultrathin nanomeshes after thermal treatment. Interestingly, the obtained CoO nanomeshes are rich in oxygen defects, providing fruitful active sites for the faradaic reaction. The modified electrode exhibits a large specific capacitance (1216.4 F g at 1 A g), as well as a high rate capability (925.5 F g at 20 A g). Moreover, an asymmetric supercapacitor made of CoO//activated carbon shows an energy density of 46.5 Wh kg at 790.7 W kg. Furthermore, the 2D CoO ultrathin nanomeshes show an outstanding performance for the oxygen evolution reaction with an overpotential of 230 mV at the onset potential and a small Tafel slope of 74.0 mV dec. The present method presents a facile avenue to the preparation of other 2D ultrathin metal oxide nanostructures with various applications in energy catalysis and conversion.

Silica‐Free Synthesis of Mesoporous Co3O4/CoOxPy as a Highly Active Oxygen Evolution Reaction Catalyst

“…Deconvolution of Co 2 + , Co 3 + , and satellite peaks are performed based on previous reports. [35][36][37] The Co 3 + /Co 2 + ratio in MÀ Co 3 O 4 is measured as 1.53 : 1, similar to but lower than that of pristine Co 3 O 4 (2 : 1), suggesting the partial surface reduction to CoO and the formation of oxygen vacancies during synthesis. [38,39] On the other hand, this value was reduced dramatically to 0.37 : 1 for MÀ Co 3 O 4 /CoO x P y , further validating the surface reduction as a result of the phosphorization.…”

“…Figure a shows the high‐resolution Co 2p spectra of M−Co 3 O 4 and M−Co 3 O 4 /CoO x P y with 2p 3/2 and 2p 1/2 splitting. Deconvolution of Co 2+ , Co 3+ , and satellite peaks are performed based on previous reports . The Co 3+ /Co 2+ ratio in M−Co 3 O 4 is measured as 1.53 : 1, similar to but lower than that of pristine Co 3 O 4 (2 : 1), suggesting the partial surface reduction to CoO and the formation of oxygen vacancies during synthesis .…”

Co3O4 Supraparticle‐Based Bubble Nanofiber and Bubble Nanosheet with Remarkable Electrochemical Performance

“…The GCD curves (Figure 5c) of the three samples show that the discharging time of RGO/HSP-Co 3 O 4 is much longer and has smaller internal resistance (IR) drop than other samples, indicating higher specific capacitance and faster reaction kinetics. [13,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] The high rate performance can be attributed to the bubble nanosheet structure and fast electrolyte diffusion inside the whole electrode. It is worth noting that 57.8% of capacitance was maintained even at a high scan rate of 200 mV s −1 , indicating that the bubble-nanosheet-structured electrode shows excellent rate performance.…”

Recent Advance in Co3O4 and Co3O4-Containing Electrode Materials for High-Performance Supercapacitors

“…This is because the organic ligand of UPC-9 prevents the agglomeration of Co 3 O 4 caused by calcination. In addition, another ultrathin Co 3 O 4 nanosheet was constructed by the zeolitic imidazolate framework-67 ( Figure 4a) [67]. The Co 3 O 4 electrode showed a large Cs of 1216.4 F•g −1 at 1 A•g −1 and a higher rate capability of 76.1% at 20 A•g −1 .…”