Electrochemical CO₂ reduction has the vast potential to neutralize CO₂ emission and valorizes this greenhouse gas into chemicals and fuels under mild conditions. Its commercial realization hinges on catalyst innovation as well as device engineering for enabling reactions at industrially relevant conditions. Copper has been widely examined for the selective production of multicarbon chemicals particularly ethylene, while there is still a substantial gap between the expected and the attainable. In this work, we report that the surface promotion of copper with alumina clusters is a viable strategy to enhance its electrocatalytic performance. AlO_x-promoted Cu catalyst is derived from Cu-Al layered double hydroxide nanosheets after alkali etching and cathodic conversion. It can catalyze CO₂ to ethylene and multicarbon products with great selectivity and stability far superior to pristine copper in both an H-cell and a zero-gap membrane electrode assembly (MEA) electrolyzer. The surface promotion effect is understood via computational simulations showing that alumina clusters can stabilize key reaction intermediates (*COOH and *OCCOH) along the reaction pathway.

Lithium–sulfur (Li–S) batteries hold great promise to be the next-generation candidate for high-energy-density secondary batteries but in the prerequisite of using low electrolyte-to-sulfur (E/S) ratios. Highly solvating electrolytes (HSEs) and sparingly solvating electrolytes (SSEs), with opposite nature towards the dissolution of polysulfides, have recently emerged as two effective solutions to decrease the E/S ratio and increase the overall practical energy density of Li–S batteries. HSEs featuring with high polysulfide solvation ability have the potential to reduce the E/S ratio by dissolving more polysulfides with less electrolyte, while SSEs alter the sulfur reaction pathway from a dissolution–precipitation mechanism to a quasi-solid mechanism, thereby independent on the use of electrolyte amount. Both HSEs and SSEs show respective effectiveness in lean-electrolyte Li–S batteries, but encounter different challenges to bring Li–S batteries into practical application. This review aims to present a comparative discussion on their unique features and basic electrochemical reaction mechanisms in practical lean-electrolyte Li–S batteries. Emphasis is focused on the current technical challenges and possible solutions for their future development.

Carbon nitride (C₃N₄) holds great promise for photocatalytic H₂O₂ production from oxygen reduction. In spite of great research efforts, they still suffer from low catalytic efficiency primarily limited by the fast recombination of photogenerated charge carriers. In this work, we report the multiscale structural engineering of C₃N₄ to significantly improve its optoelectronic properties and consequently photocatalytic performance. The product consists of porous spheres with high surface areas, abundant nitrogen defects, and alkali metal doping. Under visible light irradiation, our catalyst shows a remarkable H₂O₂ production rate of 3,080 μmol·g⁻¹·h⁻¹, which is more than 10 times higher than that of bulk C₃N₄ and exceeds those of most other C₃N₄-based photocatalysts. Moreover, the catalyst exhibits great stability, and can continuously work for 15 h without obvious activity decay under visible light irradiation, eventually giving rise to a high H₂O₂ concentration of ca. 45 mM.

Potassium-ion batteries are regarded as the low-cost alternative to lithium-ion batteries. However, their development is hampered by the lack of suitable electrode materials. In this work, we demonstrate that MoS₂ with expanded interlayers represents a promising candidate for the electrochemical storage of potassium ions. Hierarchical interlayer-expanded MoS₂ assemblies supported on carbon nanotubes are prepared via a straightforward solution method. The increased interlayer spacing not only enables the better accommodation of foreign ions, but also lowers the diffusion energy barrier and improves diffusion kinetics of ions. When investigated as the anode material of potassium ion batteries, our interlayer-expanded MoS₂ assemblies exhibit an excellent electrochemical performance with large capacity (up to ~ 520 mAh·g^-1), good rate capability (~ 310 mAh·g^-1 at 1,000 mA·g^-1) and impressive cycling stability, superior to most competitors.

Transition metal sulfides (TMSs) have a wide range of applications owing to their intriguing properties. Significant efforts have been devoted to nanostructuring TMSs to enhance their properties and performance, still there is a high need in general synthesis of TMS nanostructures. Herein, for the first time, a simple solvent free reactive nanocasting approach that integrates solid precursor loading, in-situ sulfuration and carbonization into a single heating step is developed for the universal synthesis of ordered mesoporous TMS@N-doped carbon composites (denoted as OM-TMS@NCs) with methionine (Met) and metal chlorides as the precursors and the mesoporous silica (SBA-15) as the hard template. A series of OM-TMS@NCs with a hexagonal mesostructure, ultra-high surface areas (430–754 m²·g^-1), large pore volumes (0.85–1.32 cm³·g^-1), and unique TMS stoichiometries, including MoS₂, Fe₇S₈, Co₉S₈, NiS, Cu₇S₄ and ZnS, are obtained. Two distinct structure configurations, namely, highly dispersed ultrathin TMS nanosheets within NCs and TMS@NC co-nanowire arrays, can be obtained depending on different metals. The structure evolution of the OM-TMS@NCs over the solvent-free nanocasting process is studied in detail for a deep understanding of the synthesis. As demonstrations, these materials are promising for electrocatalytic hydrogen evolution reaction and lithium ion storage with high performances.

The development of Pt-based core/shell nanoparticles represents an emerging class of electrocatalysts for fuel cells, such as methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Here, we present a one-pot synthesis approach to prepare hexagonal PtBi/Pt core/shell nanostructure composed of an intermetallic Pt₁Bi₁ core and an ultrathin Pt shell with well-defined shape, size, and composition. The structure and the synergistic effect among different components enhanced their MOR and EOR performance. The optimized Pt₂Bi nanoplates exhibit excellent mass activities in both MOR (4, 820 mA·mg_Pt^–1) and EOR (5, 950 mA·mg_Pt^–1) conducted in alkaline media, which are 6.15 times and 8.63 times higher than those of commercial Pt/C, respectively. Pt₂Bi nanoplates also show superior operation durability to commercial Pt/C. This work may inspire the rational design and synthesis of Pt-based nanoparticles with improved performance for fuel cells and other applications.

The past decade has witnessed a rapid surge of interest in the research and development of non-precious metal-based electrocatalysts for the oxygen reduction reaction (ORR). Until now, the best catalysts in acidic electrolytes have exclusively been Fe-N-C-type materials from high-temperature pyrolysis. Despite the ORR activities of metal phthalocyanine or porphyrin macrocycles having long been known, their durability remains poor. In this work, we use these macrocycles as a basis to develop a novel organic-carbon hybrid material from in-situ polymerization of iron phthalocyanine on conductive multiwalled carbon nanotube scaffolds using a low-temperature microwave heating method. At an optimal polymerto-carbon ratio, the hybrid electrocatalyst exhibits excellent ORR activity with a positive half-wave potential (0.80 V), large mass activity (up to 18.0 A/g at 0.80 V), and a low peroxide yield (< 3%). In addition, strong electronic coupling between the polymer and carbon nanotubes is believed to suppress demetallization of the macrocycles, significantly improving cycling stability in acids. Our study represents a rare example of non-precious metal-based electrocatalysts prepared without high-temperature pyrolysis, while having ORR activity in acidic media with potential for practical applications.

Nanostructured metal sulfides are potential electrode materials for sodium-ion batteries; however, they typically suffer from very poor cycling stability due to large volume changes and dissolution of discharge products. Herein we propose a rational material design strategy for sulfide-based materials to address these problems. Taking nickel sulfide (NiS_x) as an example, we demonstrated that its electrochemical performance can be dramatically improved by confining the NiS_x nanoparticles in a percolating conductive carbon nanotube network, and stabilizing them with an ultrathin carbon coating layer. The carbon layer serves as a physical barrier to alleviate the effects of both the volume change and dissolution of active materials. The hybrid material exhibited a large reversible specific capacity of > 500 mAh/g and excellent cycling stability over 200 cycles. Given the traditionally problematic nature of NiS_x as a battery anode material, we believe that the observed high performance reported here reflects the effectiveness of our material design strategy.