Controllable nanoarchitecture arrays of the transition metal selenide, supported on conductive substrates, are promising materials for high-performance electrochemical energy storage and conversion applications. Herein, Ni₃Se₂ nanowire arrays with a rich-grain-boundary are rationally grown on a nickel foam (NF) substrate by the solvothermal method. Under optimized conditions, the Ni₃Se₂ nanowire arrays prominently display high areal capacitance of 635 μA h cm⁻² at a current density of 3 mA cm⁻² and excellent rate capability. As an asymmetric supercapacitor, the Ni₃Se₂ electrode (cathode) shows a high energy density of 42.6 W h kg⁻¹ at a power density of 284.8 W kg⁻¹. When used as a two-dimensional (2D) electrode for water splitting reaction, the Ni₃Se₂ electrode exhibits high catalytic activity to achieve 100 mA cm⁻² at an overpotential of 320 mV in the oxygen evolution reaction and a low overpotential of 95 mV at a current density of 50 mA cm⁻² in the hydrogen evolution reaction in a 1.0 M KOH solution. The Ni₃Se₂ nanowire array electrode is shown to be a high-performance alkaline water electrolyzer with current density of 10 mA cm⁻² at a cell voltage of 1.62 V. The results demonstrate Ni₃Se₂ as a promising 2D highly active electrode for electrochemical energy storage and conversion applications.

The chemosynthesis of bio-renewable poly(γ-butyrolactone) (PγBL) with a high molecular weight via ring opening polymerization (ROP) of non-strained γ-butyrolactone (γBL) remains a big challenge although several catalysts have been developed in the past two years. In this contribution, we reported the efficient ROP of γBL using a strong base/urea binary synergistic catalytic system. Either an alkaline alkoxide or organophosphazene superbase was used as a strong base in this study. The base/urea binary catalyst showed high catalytic activity and high selectivity for ring opening relative to transesterification toward the ROP of γBL, and the organophosphazene superbase in combination with urea showed better catalytic activity compared to an alkaline alkoxide/urea system. The effects of bases, ureas, and reaction conditions on monomer conversions and resultant molecular weights of PγBL were systematically investigated. A PγBL homopolymer with a high molecular weight up to 35.0 kDa was synthesized using a combination of a cyclic trimeric phosphazene superbase (CTPB) and suitable ureas with electron-donating substituents. The thermal stabilities of PγBL improved dramatically with an increase in its molecular weight. The obtained PγBL exhibited unprecedented superior mechanical properties with an elongation at break of 858 ± 79%, which paves the way for its practical applications.