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The development of low-price and highly efficient catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has always been challenging with regard to water splitting. Pyrrhotite Fe7S8 has become a research hotspot due to its abundant reserves, high electrical conductivity and excellent catalytic activity. In general, introducing metal heteroatoms into transition metal sulfides (TMSs) can effectively enhance the activity and stability of TMSs. Herein, Co-doped pyrrhotite Fe7S8 nanosheets were obtained by a straightforward two-step method consisting of hydrothermal treatment followed by subsequent heat treatment. Results from XPS analysis and contact angle measurements showed that doping optimized the chemical environment around iron atoms and enhanced the adsorption of water molecules on the surface of Fe7S8, thereby greatly improving the electrocatalytic efficiency of water electrolysis. Compared with other counterparts, Co0·95Fe6·05S8 exhibited superior OER activity with an overpotential of 311 mV at a current density of 10 mA cm−2, and higher performance towards HER with an overpotential of 284 mV at 10 mA cm−2 in alkaline solution. In sum, Co0·95Fe6·05S8 is promising as a bifunctional catalyst for water splitting under alkaline conditions.

Nanoarchitecture materials are widely investigated to enhance hydrogen evolution reaction (HER) performance. However, it is beset with difficulties to obtain nanomaterials at industrial-scale in comparison with bulk materials. Herein, bulk electrocatalyst Fe4.5Ni4.5S8/Fe7S8 is prepared using flotation method and alkali cleaning from natural nickel ore. Sulfur vacancies and electron interaction between Fe7S8 and Fe4.5Ni4.5S8 may efficiently reduce hydrogen adsorption energy's absolute value, thus significantly improving hydrogen production efficiency. Hybrid catalyst requires ultralow overpotential of 48 mV at 10 mA cm−2 for HER in 0.5 M H2SO4 and exhibits high stability (maintaining an almost constant overpotential after 20,000 cyclic voltammetry sweeps). Therefore, it can be affirmed that it demonstrates promising industrial application as an electrocatalyst towards HER.

We performed dynamic Monte Carlo simulations of random copolymers containing variable sliding mobility of non-crystallizable comonomer sequences (reflecting their relative sizes) in the crystalline monomer regions. Upon raising strains, we observed that the comononer sliding mobility does not affect the strain evolution curves of crystallinity. However, in the middle temperature region, the low mobility causes a delay of switching from the intra-molecular to the inter-molecular modes of crystal nucleation in the copolymers holding low fractions of comonomers. We attributed the effect to the difficulty of comonomers to be excluded from the nucleating domains that are limited by sequence segregation in the oriented amorphous segments. The implication of this effect to the efficiency of crystal nucleation upon cyclic loading has been discussed.

We developed a linear combination of two Flory’s melting-point theories, one for stretched and the other for solution polymers, to predict the melting point of stretched solution polymers. The dependences of the melting strains on varying temperatures, polymer volume fractions, and solvent qualities were verified by the onset strains of crystallization in our dynamic Monte Carlo simulations of stretched solution polymers under a constant strain rate. In addition, owing to phase separation before crystallization in a poor solvent, calibration of polymer concentration to the polymer-rich phase appears necessary for the verification. Our results set up a preliminary thermodynamic background for the investigation of the multicomponent effect on strain-induced crystallization of polymers in rubbers and gels as well as on shear-induced crystallization of polymers in solutions and blends.

The self-assembly structures and their transformation of blends of rod−coil−rod triblock copolymers and homopolymers were first detected. Adding coil homopolymers into block copolymers with a lamellar structure resulted in an increase of d-spacing. When coil homopolymers were added into triblock copolymer with a rod continuous hexagonally packed-cylinder structure, lamellar structures were obtained, and the lamellar d-spacing were smaller than that of the original structure. The addition of rod-like homopolymer into the block copolymers with a lamellar structure also resulted in the increase of the d-spacing. As a result of the interdigitation, the rod blocks must rearrange to a larger angle with respect to the interface.

The cationic grafting polymerization of isobutylene (IB) from a poly(vinyl acetate) (PVAc) backbone was initiated by the combination of PVAc with titanium tetrachloride (TiCl4) in methylene chloride (CH2Cl2) solution at –65°C. A mixture of IB homopolymer and PVAc grafted with approximately 9.5% (mol) PIB copolymer was formed. 1H- and 13C-NMR spectra confirmed that IB was successfully grafted from the PVAc backbone. PVAc exhibits both initiation and modification behavior. PVAc acts as a macro-initiator in the polymerization to form the graft copolymer. It also plays a role in the homopolymerization of IB initiated by the combination of residual water with TiCl4 and the product PIB with a narrow molecular weight distribution.

The cationic polymerization of isobutylene coinitiated by Al(i-Bu)Cl2(Al) was carried out in mixed butane–butene fractions at −50 °C. The expected polymerization processes induced by the trace of moisture with Al system in the presence of a small amount of external electron-donor modifiers, such as methyl acrylate (MA) and dimethyl sulfoxide (DMSO), were obtained. The experimental results showed that these polymerizations produced polymers with relatively high number-average molecular weights and narrow molecular weight distributions (1.5–2.2). That the gel permeation chromatography traces of the polymers depended on the types and concentrations of external donors suggested that there existed competitive complexation reactions of various electron donors (H2O, MA, and DMSO) with the Al Lewis acid. The roles of external electron donors were to take part in the initiation step by competitive complexation and to modify the reactivity of the growing chain ends in the propagation step by mediation and/or solvation, which impaired the high reactivity of the original growing chain ends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2209–2214, 2002

The cationic polymerizations of isobutylene (IB) initiated by the H2O/TiCl4 in dichloromethane (CH2Cl2) at −30 °C were carried out in the absence and presence of various external electron pair dono...