The mitochondrial respiratory Complex II or succinate:ubiquinone oxidoreductase (SQR) is an integral membrane protein complex in both the tricarboxylic acid cycle and aerobic respiration. Here we report the first crystal structure of Complex II from porcine heart at 2.4 A resolution and its complex structure with inhibitors 3-nitropropionate and 2-thenoyltrifluoroacetone (TTFA) at 3.5 A resolution. Complex II is comprised of two hydrophilic proteins, flavoprotein (Fp) and iron-sulfur protein (Ip), and two transmembrane proteins (CybL and CybS), as well as prosthetic groups required for electron transfer from succinate to ubiquinone. The structure correlates the protein environments around prosthetic groups with their unique midpoint redox potentials. Two ubiquinone binding sites are discussed and elucidated by TTFA binding. The Complex II structure provides a bona fide model for study of the mitochondrial respiratory system and human mitochondrial diseases related to mutations in this complex.

lithium-sulfur, sodium-, magnesium-, and aluminum-based batteries. [2] Among these competitors, lithium-sulfur battery (LSB) is a promising candidate since the earth-abundant sulfur has a high theoretical capacity of 1675 mAh g −1 and LSB provides a high theoretical energy density of 2600 Wh kg −1 or 2800 Wh l −1 . [3] Nevertheless, the practical application of LSB is still limited by the poor electric/ionic conductivity of sulfur and the "shuttle effect" caused by the dissolution and diffusion of lithium polysulfides (LiPSs), resulting in an uncompetitive capacity, rate performance, and cycling life. [4] To address these issues, intensive studies have been done, such as cathode design, separator modification, electrolyte optimization, and anode protection. [5] LiPSs immobilization and LiPSs ↔ Li 2 S 2 /Li 2 S conversion acceleration are two major considerations for LSB cathode design. [6] The anchoring and catalyzing effect of various candidates (such as metal oxides/sulfide/nitride) have been investigated by first principle calculations [7] or quantitative adsorption experiments. [8] Although some species show strong chemical interactions with LiPSs or effective catalysis on the conversion reaction, battery performances have been largely restrained by the poor electronic/ionic conductivity As the lightest member of transition metal dichalcogenides, 2D titanium disulfide (2D TiS 2 ) nanosheets are attractive for energy storage and conversion. However, reliable and controllable synthesis of single-to few-layered TiS 2 nanosheets is challenging due to the strong tendency of stacking and oxidation of ultrathin TiS 2 nanosheets. This study reports for the first time the successful conversion of Ti 3 C 2 T x MXene to sandwich-like ultrathin TiS 2 nanosheets confined by N, S co-doped porous carbon (TiS 2 @NSC) via an in situ polydopamine-assisted sulfuration process. When used as a sulfur host in lithium-sulfur batteries, TiS 2 @NSC shows both high trapping capability for lithium polysulfides (LiPSs), and remarkable electrocatalytic activity for LiPSs reduction and lithium sulfide oxidation. A freestanding sulfur cathode integrating TiS 2 @NSC with cotton-derived carbon fibers delivers a high areal capacity of 5.9 mAh cm −2 after 100 cycles at 0.1 C with a low electrolyte/sulfur ratio and a high sulfur loading of 7.7 mg cm −2 , placing TiS 2 @NSC one of the best LiPSs adsorbents and sulfur conversion catalysts reported to date. The developed nanospace-confined strategy will shed light on the rational design and structural engineering of metal sulfides based nanoarchitectures for diverse applications.

Different classes of coating materials with their functional groups and mechanism of interaction with PSs.

Lithium–sulfur batteries (LSBs) have attracted tremendous interest due to their high theoretical energy density and the earth‐abundant sulfur feedstock. Multifarious characterization techniques have been applied to investigate the electrochemical mechanisms and the structure–property relationships in LSBs. Among them, cyclic voltammetry (CV), a basic electrochemical tool, can provide indispensable thermodynamic and kinetics information of the redox processes. However, the CV analysis in most LSB studies is sketchy—providing some well‐known information while ignoring some specific features. To fulfill the versatile role of CV and thus spur further breakthroughs on LSBs, the electrochemical reactions and challenges are first described, followed by the work principles and experimental setup of LSBs for the CV technique. Then, various protocols for specific research purposes in LSBs are summarized, particularly on the performance evaluation of sulfur cathodes. Ending with challenges and the outlook of the CV technique in the LSB study, the Review provides a timely summary and thus can be a guidance for future studies on batteries.