Chao Wang

Ordered microphase separation via fluorinated side-chain engineering creates continuous proton pathways and dense vanadium-blocking domains.

Alkaline water electrolysis for hydrogen production suffers from the easy surface reconstruction of transition metal selenides during the oxygen evolution reaction (OER), while their real active phase and structural evolution remain unclear. Herein, a self-supported CoSe@Ni3Se4/NF heterojunction pre-catalyst was constructed by hydrothermal selenization of a NiCo-MOF, which induced Ni/Co phase separation. In situ Raman spectroscopy captured the dynamic surface reconstruction: above 1.3 V, the surface converted in situ to M-OOH (NiOOH/CoOOH) as the real active phase, while the internal heterojunction skeleton stayed intact, revealing a synergy of "surface reconstruction generating activity, internal stability ensuring longevity". Owing to the coupling of interfacial electron redistribution and surface reconstruction, the catalyst delivered overpotentials of only 104 mV for HER and 219 mV for OER at 10 mA cm-2 in 1 M KOH, with an OER Tafel slope as low as 44 mV dec-1, superior to commercial RuO2/NF. An overall water splitting device required only 1.546 V to reach 10 mA cm-2 and remained stable for 72 h. This work provides a new strategy for phase-separation engineering of MOF-derived heterojunctions and sheds light on the dynamic reconstruction of transition metal selenides.

The inherent trade-off between proton conductivity and vanadium-ion selectivity remains a critical barrier for ion-exchange membranes in vanadium redox flow batteries. Herein, we report a molecular-level ion–dipole confinement strategy to address this challenge. By incorporating carbazole comonomers bearing flexible ether-containing C6O2 side chains into a poly(terphenyl-piperidine) backbone and subsequently grafting alkylsulfonate groups, we constructed amphoteric membranes in which ether oxygen atoms interact intimately with sulfonate moieties. These ion–dipole interactions anchor the sulfonate-bearing side chains, restrict their hydration-driven segmental motion, and suppress macroscopic swelling while preserving the connectivity of hydrophilic domains. The optimized membrane exhibits a proton conductivity of 135 mS cm-1, a low area resistance of 0.34 Ω cm2, and significantly reduced vanadium permeability. In a single-cell test, the membrane achieves a coulombic efficiency of 99% and an energy efficiency of 71% at 260 mA cm-2, with stable long-term cycling over 300 cycles. This work establishes a general design principle—using ion–dipole interactions to decouple swelling from ion transport—that can be extended to other flow battery systems, water treatment, and various ion-selective separation applications.

Developing non-noble metal bifunctional catalysts with high stability and sustained activity is essential for alkaline water splitting. Herein, we report a cobalt-iron bimetallic phosphoselenide (P,Se-CoFe/NF) catalyst synthesized via a two-step approach combining hydrothermal growth and low-temperature phosphoselenization. The dual doping of phosphorus and selenium effectively modulates the electronic structure and enriches the active sites of the CoFe matrix, thereby enhancing the catalytic selectivity and activity for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Benefiting from these advantages, the P,Se-CoFe/NF catalyst delivers exceptional bifunctional performance in alkaline media: it requires only 205 mV and 141 mV overpotential to achieve a current density of 10 mA·cm-2 for OER and HER, respectively. Moreover, an overall water splitting cell using this catalyst as both anode and cathode attains 10 mA·cm-2 at a low voltage of 1.576 V. This work provides a feasible and efficient strategy for designing non-noble metal electrocatalysts toward practical alkaline water electrolysis.

Traditional anion exchange membranes (AEMs) inherently suffer from a trade-off between high ionic conductivity and excessive swelling. Polyimides, which offer a combination of exceptional mechanical properties, dimensional stability, and structural designability, are highly promising alternative substrates for AEMs. However, their application is hindered by the long-standing bottleneck of the imide ring's susceptibility to alkaline hydrolysis, resulting in severely limited research in this area. In this work, we propose a molecular design strategy based on synergistic bifunctional block phase separation. A chemically phase-separated architecture was constructed, comprising a trifluoromethyl-based hydrophobic block to provide steric hindrance and a hydrophobic barrier, alongside a benzimidazole-based hydrophilic block that is alkaline-resistant and quaternizable. The microphase-separated structure was precisely optimized by tuning the block ratio. This strategy significantly inhibits the hydrolysis of the imide ring through bifunctional synergy. Simultaneously, by leveraging bicontinuous microphase separation to construct continuous, low-resistance OH- transport channels, we successfully decoupled the trade-off between conductivity and swelling. The optimal QAPI-70 membrane achieved a conductivity of 130.2 mS·cm-1 with a swelling ratio of only 22% at 80 ℃. Furthermore, it retained 88.7% of its initial conductivity after aging in 1 M NaOH at 80 ℃ for 1000 hours. MD simulations further confirmed that QAPI-70 possesses the optimal microphase-separated structure and OH- transport performance. AEMWE cell based on this membrane delivered a current density of 1050 mA·cm-2 at 1.8 V and 60 ℃, operating stably for 50 hours. This work provides a new paradigm for the development of high-performance polyimide-based AEMs.

Manganese-regulated polymetallic ZIF derivatives: Highly efficient bifunctional water electrolysis catalysts prepared via electrodeposition and low-temperature annealing.