Electrochemical water splitting is a clean technology for H2 fuels, but greatly hindered by the slow kinetics of the oxygen evolution reaction (OER). Herein, a series of spinel-structured nanosheets with oxygen deficiencies and ultrathin thicknesses were designed to increase the reactivity and the number of active sites of the catalysts, which were then taken as an excellent platform for promoting the water oxidation process. Theoretical investigations showed that the oxygen vacancies confined in the ultrathin nanosheet could lower the adsorption energy of H2O, leading to increased OER efficiency. As expected, the NiCo2O4 ultrathin nanosheets rich in oxygen vacancies exhibited a large current density of 285 mA cm(-2) at 0.8 V and a small overpotential of 0.32 V, both of which are superior to the corresponding values of bulk samples or samples with few oxygen deficiencies and even higher than those of most reported non-precious-metal catalysts. This work should provide a new pathway for the design of advanced OER catalysts.

The transferring and identification of single- and few- layer graphene sheets from SiO2/Si substrates to other types of substrates is presented. Features across large areas (∼cm2) having single and few-layer graphene flakes, obtained by the microcleaving of highly oriented pyrolytic graphite (HOPG), can be transferred reliably. This method enables the fast localization of graphene sheets on substrates on which optical microscopy does not allow direct and fast visualization of the thin graphene sheets. No major morphological deformations, corrugations, or defects are induced on the graphene films when transferred to the target surface. Moreover, the differentiation between single and bilayer graphene via the G′ (∼2700 cm−1) Raman peak is demonstrated on various substrates. This approach opens up possibilities for the fabrication of graphene devices on a substrate material other than SiO2/Si.

We demonstrate here a PMMA-mediated nanotransfer printing technique for reliably transferring nanoscale building blocks and sequentially building purpose-directed nanostructures. The utilization of PMMA film as a mediator introduced several features to this transfer approach, such as high efficiency, fidelity, universality, controllability, and multilevel transferability. Various nanostructures, such as an SWNTs-on-SAM structure, high-density crossbar array of SWNTs, a hybrid n-ZnO nanowire/p-SWNT cross-junction, a gold nanostructure-SAM-gold sandwich structure, a zigzag array of SWNTs, and gold nanobowl array were generated with this transfer approach. A metallic-semiconducting SWNT cross circuit was built to demonstrate its potential application in fabricating nanoelectronic devices. This technique paves the way to generate various structures with homo- or heterogeneous nanoscale building blocks, which facilitates exploring their fundamental properties and building novel devices.

Electrochemical water splitting is aclean technology for H 2 fuels,b ut greatly hindered by the slowk inetics of the oxygen evolution reaction (OER). Herein, as eries of spinelstructured nanosheets with oxygen deficiencies and ultrathin thicknesses were designed to increase the reactivity and the number of active sites of the catalysts,which were then taken as an excellent platform for promoting the water oxidation process.T heoretical investigations showed that the oxygen vacancies confined in the ultrathin nanosheet could lower the adsorption energy of H 2 O, leading to increased OER efficiency.A se xpected, the NiCo 2 O 4 ultrathin nanosheets rich in oxygen vacancies exhibited al arge current density of 285 mA cm À2 at 0.8 Va nd as mall overpotential of 0.32 V, both of whichare superior to the corresponding values of bulk samples or samples with few oxygen deficiencies and even higher than those of most reported non-precious-metal catalysts.This work should provideanew pathwayfor the design of advanced OER catalysts.Electrochemical and photochemical water splitting have been regarded as promising approaches for energy storage and conversion and utilize electric energy to split abundant water into clean H 2 fuel. [1][2][3][4] Amongt he electrochemical processes,the oxygen evolution reaction (OER) is efficiencylimiting owing to the complex four-electron redox process, and thus hinders the large-scale application of electrochemical water splitting. [5][6][7] Generally speaking, an appropriate OER catalyst is required to address the kinetically slow process.Among all tested candidates,ruthenium and iridium oxides are known to exhibit the best overall performances but their use is limited by their scarcity and high cost. [8,9] Accordingly,m uch efforts have been devoted to searching for alternative OER electrocatalysts that are based on abundant and economic 3d metals and their derivatives. [10][11][12][13][14][15] Among these non-precious-metal catalysts,s pinel-structured oxides,w ith their high electronic conductivity and stability, have exhibited asuperior performance in the OER. However, their electrocatalytic performance is still far from the requirements of practical applications.T he design of simple and economic alternative routes to obtain highly active nonprecious-metal catalysts will be key for the development of electrocatalytic water oxidation.Active sites play the key role in catalytic processes. Therefore,increasing the reactivity and number of active sites will be two effective ways to enhance electrocatalytic performance.A sapromising structural motif for realizing ag reat number of active sites,t wo-dimensional (2D) nanosheets with ultrathin thickness possess the maximum number of electroactive surface/active sites,w hich can also lead to adecrease in the length of the diffusion paths of ions and an increase in the contact area with the electrolyte.S uch materials are thus suitable candidates for the realization of highly efficient catalysts for electrochemical processes. [16][17][18]

No abstract

No abstract

No abstract

We herein report a facile strategy to prepare triggered degradable block copolymer nano/macro-objects, ranging from typical micelles, worms, jellyfish, and vesicles to rarely achieved spongosomes, cubosomes, and hexosomes via RAFT-mediated polymerizationinduced self-assembly (PISA). The morphological transitions from a simple spherical micelle to a spongosome, ordered Im ̅ 3m cubosome, and p6mm hexosome were captured and demonstrated by TEM, SEM, and synchrotron SAXS. In addition, morphological phase diagrams including important factors, such as solid contents, degree of polymerization (DP), and stabilizer block chain length, were constructed to unveil the formation mechanism and guide the scalable preparation of complex morphologies with packing parameter (P) > 1. This study not only represents an example that achieved inverse mesophases via acrylate-based monomers with high conversion but also reports a triggered degradable system in the most extended morphological range via PISA. The facile synthesis and stimuli-responsiveness of our system should greatly expand the utility of polymer inverse mesophases for triggered releasing, templating, and many other applications.