Interface engineering of porous Fe2P-WO2.92 catalyst with oxygen vacancies for highly active and stable large-current oxygen evolution and overall water splitting

Constructing a low cost,and high-efficiency oxygen evolution reaction(OER)electrocatalyst is of great significance for improving the performance of alkaline electrolyzer,which is still suffering from highenergy consumption.Herein,we created a porous iron phosphide and tungsten oxide self-supporting electrocatalyst with oxygen-containing vacancies on foam nickel(Fe₂P-WO_2.92/NF)through a facile insitu growth,etching and phosphating strategies.The sequence-controllable strategy will not only generate oxygen vacancies and improve the charge transfer between Fe₂P and WO_2.92 components,but also improve the catalyst porosity and expose more active sites.Electrochemical studies illustrate that the Fe₂P-WO_2.92/NF catalyst presents good OER activity with a low overpotential of 267 mV at 100 mA cm^-2,a small Tafel slope of 46.3 mV dec^-1,high electrical conductivity,and reliable stability at high current density(100 mA cm^-2 for over 60 h in 1.0 M KOH solution).Most significantly,the operating cell voltage of Fe₂P-WO_2.92/NF‖Pt/C is as low as 1.90 V at 400 mA cm^-2 in alkaline condition,which is one of the lowest reported in the literature.The electrocatalytic mechanism shows that the oxygen vacancies and the synergy between Fe₂P and WO_2.92 can adjust the electronic structure and provide more reaction sites,thereby synergistically increasing OER activity.This work provides a feasible strategy to fabricate high-efficiency and stable non-noble metal OER electrocatalysts on the engineering interface.     

Bio-smart materials: kinetics of immobilized enzymes in p(HEMA)/p(pyrrole) hydrogels in amperometric biosensors

Various strategies are being pursued to confer the highly specific molecular recognition properties of bioactive molecules to the transducer action of inherently conductive polymers. We have successfully integrated inherently conductive polypyrrole within electrode-supported, UV cross-linked hydroxyethyl methacrylate (HEMA)-based hydrogels. These electroactive composites were used as matrixes for the physical immobilization of several oxidase enzymes to fabricate clinically important biosensors. Measurements were made of the amperometric responses via H₂O₂ oxidation for each biosensor. Apparent Michaelis constants, K_m(app), for glucose oxidase immobilized in p(HEMA) membranes and in p(HEMA)/p(Pyrrole) composite membranes were 13.8 and 43.7 mM respectively compared to 33 mM in solution. The inclusion of polypyrrole in the hydrogel network increased the thermal stability of the immobilized enzyme at 60°C by 30% and 40% compared to p(HEMA) membranes and solution phase respectively. The composite also yielded larger I_max values (19 μA/cm⁻²) for glucose biosensors compared to similar glucose biosensors fabricated without the conducting polymer (15 μA). K_m(app) values for cholesterol oxidase immobilized in the same composite films were ca. three orders of magnitude higher than the K_m for the soluble enzyme. The polypyrrole component is shown to reduce diffusive transport but to confer thermal stability to these biosensors.     

Formation,structure and properties of polymer networks: gel‐point prediction in endlinking polymerisations

Gel points, predicted using Ahmed‐Rolfes‐Stepto (ARS) theory and a Monte‐Carlo (MC) simulation method accounting for intramolecular reaction, are compared with experimental data for polyester (PES)‐, polyurethane (PU)‐ and poly(dimethyhl siloxane) (PDMS)‐forming polymerisations. The PES and PU polymerisations were from stoichiometric reactions at different initial dilutions and the PDMS ones were from critical‐ratio experiments at different dilutions of one reactant. The predictions use realistic chain statistics to define intramolecular reaction probabilities and employ no arbitrary parameters. Universal plots of excess reaction at gelation versus ring‐forming parameter are devised to enable the experimental data and theoretical predictions to be compared critically. It is shown that various gel points can be predicted by MC simulations, depending on the criterion for gelation used. Due to the lengthy computations needed and the uncertainties in the predictions, MC simulation is not a viable approach. Although inconsistencies are noted in the measured gel points, so that a unified interpretation of the data cannot be achieved, ARS theory is shown to be the preferred basis for gel‐point prediction. It is also concluded that, before one can be certain of agreement between experiment and predictions, more experimental systems at different initial dilutions and ratios of reactants need to be studied and the various methods used for detecting gel points need to be compared.     

Creation of novel polymer materials by processing with inclusion compounds

The processing of polymer materials from their inclusion compounds (ICs) formed with urea (U) and cyclodextrin (CD) hosts is described. Several examples are presented and serve to demonstrate the fabrication of unique polymer‐polymer composites and blends, including intimate blends of normally incompatible polymers, and the delivery of additives to polymers by means of embedding polymer‐ or additive‐U and CD‐ ICs into carrier polymer films and fibers, followed by coalescence of the IC guest, or by coalescence of two polymers or a polymer and an additive from their common CD‐IC crystals.     

Λ‐{1,4,7,10‐Tetrakis­[(S)‐2‐hydroxy­propyl‐κO]‐1,4,7,10‐tetra­aza­cyclo­do­decane‐κ4N}cadmium(II) bis(2,4,6‐tri­nitro­phenolate) aceto­nitrile solvate

Crystallization of [Cd(S‐thpc12)](ClO₄)₂·H₂O {S‐thpc12 is 1,4,7,10‐tetrakis­[(S)‐2‐hydroxy­propyl]‐1,4,7,10‐tetra­aza­cyclo­do­decane} in the presence of two equivalents of sodium picrate monohydrate (sodium 2,4,6‐tri­nitro­phenolate monohydrate) diastereoselectively produces a neutral receptor complex, viz. the title compound, Λ‐[Cd(C₂₀H₄₄N₄O₄)](C₆H₂N₃O₇)₂·CH₃CN. In this complex, two picrate anions hydrogen bond, via their phenolate moieties, to the pendant hydroxyl groups of the receptor which, together with the four N atoms, themselves bond to Cd^II in an approximately cubic arrangement. One picrate anion hydrogen bonds to all four hydroxyl groups, one of which also acts as the sole hydrogen‐bond donor to the second picrate anion.