This study focuses on optimizing catalytic activity in photocatalytic hydrogen evolution reaction by precisely designing and modulating the electronic structure of metal single atoms. The catalyst, denoted as PtSA@S-TFPT, integrates low-valence platinum single atoms into sulfur-containing covalent organic frameworks. The robust asymmetric four-coordination between sulfur and platinum within the framework enables a high platinum loading of 12.1 wt%, resulting in efficient photocatalytic hydrogen production activity of 11.4 mmol g⁻¹ h⁻¹ and stable performance under visible light. These outcomes are attributed to a reduced hydrogen desorption barrier and enhanced photogenerated charge separation, as indicated by density functional theory calculations and dynamic carrier analysis. This work challenges traditional notions and opens an avenue for developing low-valence metal single atom-loaded covalent organic framework catalysts to advance photocatalytic hydrogen evolution.

We report a polysiloxane based single-ion conducting polymer electrolyte (SIPE) synthesized via a hydrosilylation technique. Styrenesulfonyl(phenylsulfonyl)imide groups were grafted on highly flexible polysiloxane chains followed by lithiation. The highly delocalized anionic charges in the grafted moiety give rise to weak association with lithium ions in the polymer matrix, resulting in a lithium ion transference number close to unity (0.89) and remarkably high ionic conductivity (7.2 × 10⁻⁴ S cm⁻¹) at room temperature. The high flexibility arising from polysiloxane enables the glass transition temperature (T_g) to be below room temperature. The electrolyte membrane displays high thermal stability and a strong mechanical strength. A coin cell assembled with the membrane comprised of the electrolyte and poly(vinylidene-fluoride-co-hexafluoropropene) (PVDF-HFP) performs remarkably well over a wide range of temperatures with high charge–discharge rates.

Li–S secondary batteries use lithium metal as the anode. The safety hazard arising from the Li dendrite formation on the metal surface presents a formidable challenge that has hindered the technology from practical applications for many years. It has been confirmed that tiny and random lithium deposition takes place at the ion depletion layer on the surface of lithium metal. The time required to reach the ion depletion layer can be quantified using Sand's equation, in which the time is inversely proportional to the transference number of anions (t₋). Therefore, restricting the mobility of anions enables avoidance of ion depletion. In this study, lithium 4-aminophenylsulfonyl(trifluoromethylsulfonyl)imide (LiATFSI) is grafted with poly(ethylene-alt-maleic anhydride) (PEMA, M_w = 100 000–500 000) using a cyclic imide to form a single ion conducting polymer electrolyte (PEMA-graft-LiATFSI). The polymer electrolyte membrane made of PEMA-graft-LiATFSI is capable of withstanding a high current density of ±50 mA cm⁻² (normalized to the surface area of the lithium disk) in a lithium symmetric cell. More remarkably, the metallic luster of the lithium foil remains essentially intact even after a galvanostatic cycling test with a current density of ±10 mA cm⁻² for over 1600 hours, suggesting that the membrane can effectively suppress Li dendrite formation and thus pave a way to use lithium metal directly as the anode material with sufficient energy capacity and good safety. The lithium–sulfur battery assembled with the membrane as the electrolyte as well as the separator delivered a stable capacity of 780.8 mA h g⁻¹ after 1000 cycles at 1C. This work demonstrates the necessity and fundamental importance of single ion conducting electrolyte membranes for achieving safe and stable performance with high energy density lithium metal secondary batteries.

Concentration polarization issues and lithium dendrite formation, which associate inherently with the commercial dual-ion electrolytes, restrict the performance of lithium ion batteries. Single ion conducting polymer electrolytes (SIPEs) with high lithium ion transference numbers (t₊ ≈ 1) are being intensively studied to circumvent these issues. Herein, poly(ethylene-co-vinyl alcohol) (EVOH) is chosen as the backbone and then grafted with lithium 3-chloropropanesulfonyl(trifluoromethanesulfonyl)imide (LiCPSI) via Williamson's reaction, resulting in a side-chain-grafted single ion polymer conductor (EVOH-graft-LiCPSI). The ionomer is further blended with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) by solution casting for practical use. The SIPE membrane with ethylene carbonate and dimethyl carbonate (EC/DMC = 1 : 1, v/v) as plasticizer (i.e., gel SIPE) exhibits an ionic conductivity of 5.7 × 10⁻⁵ S cm⁻¹, a lithium ion transference number of 0.88, a wide electrochemical window of 4.8 V (vs. Li/Li⁺) and adequate mechanical strength. Finally, the gel SIPE is applied in a lithium ion battery as the electrolyte as well as the separator, delivering an initial discharge capacity of 100 mA h g⁻¹ at 1C which remains at 95 mA h g⁻¹ after 500 cycles.