Ultra-Low-Dose Pre-Metallation Strategy Served for Commercial Metal-Ion Capacitors.

HIGHLIGHTS: Interfacial bonding strategy has been successfully applied to address the high overpotential issue of sacrificial additives, which reduced the decompositon potential of Na2C2O4 from 4.50 to 3.95 V. Ultra-low-dose technique assisted commercial sodium ion capacitor (AC//HC) could deliver a remarkable energy density of 118.2 Wh kg-1 as well as excellent cycle stability. In-depth decomposition mechanism of sacrificial compound and the relative influence after pre-metallation were revealed by advanced in situ and ex situ characterization approaches. Sacrificial pre-metallation strategy could compensate for the irreversible consumption of metal ions and reduce the potential of anode, thereby elevating the cycle performance as well as open-circuit voltage for full metal ion capacitors (MICs). However, suffered from massive-dosage abuse, exorbitant decomposition potential, and side effects of decomposition residue, the wide application of sacrificial approach was restricted. Herein, assisted with density functional theory calculations, strongly coupled interface (M-O-C, M = Li/Na/K) and electron donating group have been put forward to regulate the band gap and highest occupied molecular orbital level of metal oxalate (M2C2O4), reducing polarization phenomenon and Gibbs free energy required for decomposition, which eventually decrease the practical decomposition potential from 4.50 to 3.95 V. Remarkably, full sodium ion capacitors constituted of commercial materials (activated carbon//hard carbon) could deliver a prominent energy density of 118.2 Wh kg-1 as well as excellent cycle stability under an ultra-low dosage pre-sodiation reagent of 15-30 wt% (far less than currently 100 wt%). Noteworthily, decomposition mechanism of sacrificial compound and the relative influence on the system of MICs after pre-metallation were initially revealed by in situ differential electrochemical mass spectrometry, offering in-depth insights for comprehending the function of cathode additives. In addition, this breakthrough has been successfully utilized in high performance lithium/potassium ion capacitors with Li2C2O4/K2C2O4 as pre-metallation reagent, which will convincingly promote the commercialization of MICs.

Electronic Effect and Regiochemistry of Substitution in Pre-sodiation Chemistry.

The low oxidation potential of a pre-sodiation cathode additive intrinsically prevents decomposition of the electrolyte. Although the introduction of electron-donating substitution reduces the oxidation potential, the additional molecular weight restricts the output capacity. Herein, as theroretically predicted, the electrochemical oxidation potential of sodium carboxylate is manipulated by the electronic effect and regiochemistry of the functionality, in which the stronger electron-donating substituent, p-π conjugation, and optimized regiochemistry can dramatically lead to the lower potential originated from the elevation of the highest occupied molecular orbital level. Thus, benefiting from the para-NH2 unit accompanied by a conjugated aromatic architecture, molecularly engineered sodium para-aminobenzoate (PABZ-Na) presents a reduced oxidation plateau of 3.45 V. Triggered by the positive compensation merit, sodium-based electrochemical storage systems manifest excellent electrochemical performances. This breakthrough sheds light into the correlation between the electronic effect of the functional group and the oxidation potential of the organic additive, affording in-depth insights into the fundamental guidance of pre-sodiation chemistry.

Mussel-inspired surface modification of titania nanotubes as a novel drug delivery system.

Titania nanotubes (TNTs) have attracted considerable attention for the development of new devices for local drug delivery applications. In this study TNTs were synthesized by hydrothermal method from titania nanoparticles and then the surface of TNTs were functionalized by in situ polymerization of bioinspired polydopamine (PDA). The proposed strategies emphasized on remarkable properties of these materials and their unique combination to design local drug delivery system with advanced performance. The samples were characterized using Transmission Electron Microscope (TEM), Field Emission Scanning Electron Microscope (FESEM), X-ray diffraction pattern (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and surface area analysis (BET). The results showed that the specific surface area significantly is increased by creating tubular nanostructure. TGA results indicated Surface functionalization of TNTs with PDA (TNTs-PDA) about 19.3% that led to increase biocompatibility and bioactivity of TNTs as well as improve drug loading and release properties. It is attributed to the effect of NH2 groups which immobilize drug molecules on the TNTs. According to the obtained release profiles for the samples, the release profiles followed from a Hill model. Thus, PDA modified TNTs can be excellent candidate as specific drug delivery systems.