Alloying at a Subnanoscale Maximizes the Synergistic Effect on the Electrocatalytic Hydrogen Evolution

Advanced Bismuth-Based Anode Materials for Efficient Potassium Storage: Structural Features, Storage Mechanisms and Modification Strategies

Potassium-ion batteries (PIBs) are considered as a promising energy storage system owing to its abundant potassium resources. As an important part of the battery composition, anode materials play a vital role in the future development of PIBs. Bismuth-based anode materials demonstrate great potential for storing potassium ions (K+) due to their layered structure, high theoretical capacity based on the alloying reaction mechanism, and safe operating voltage. However, the large radius of K+ inevitably induces severe volume expansion in depotassiation/potassiation, and the sluggish kinetics of K+ insertion/extraction limits its further development. Herein, we summarize the strategies used to improve the potassium storage properties of various types of materials and introduce recent advances in the design and fabrication of favorable structural features of bismuth-based materials. Firstly, this review analyzes the structure, working mechanism and advantages and disadvantages of various types of materials for potassium storage. Then, based on this, the manuscript focuses on summarizing modification strategies including structural and morphological design, compositing with other materials, and electrolyte optimization, and elucidating the advantages of various modifications in enhancing the potassium storage performance. Finally, we outline the current challenges of bismuth-based materials in PIBs and put forward some prospects to be verified.

Sub-1 nm Materials Chemistry: Challenges and Prospects

Subnanometer materials (SNMs) refer to nanomaterials with a feature size close to 1 nm, similar to the diameter of a single polymer, DNA strand, and a single cluster/unit cell. The growth and assembly of subnanometer building blocks can be controlled by interactions at atomic levels, representing the limit for the precise manipulation of materials. The size, geometry, and flexibility of 1D SNMs inorganic backbones are similar to the polymer chains, bringing excellent gelability, adhesiveness, and processability different from inorganic nanocrystals. The ultrahigh surface atom ratio of SNMs results in significantly increased surface energy, leading to significant rearrangement of surface atoms. Unconventional phases, immiscible metal alloys, and high entropy materials with few atomic layers can be stabilized, and the spontaneous twisting of SNMs may induce the intrinsic structural chirality. Electron delocalization may also emerge at the subnanoscale, giving rise to the significantly enhanced catalytic activity. In this perspective, we summarized recent progress on SNMs, including their synthesis, polymer-like properties, metastable phases, structural chirality, and catalytic properties, toward energy conversion. As a critical size region in nanoscience, the development of functional SNMs may fuse the boundary of inorganic materials and polymers and conduce to the precise manufacturing of materials at atomic levels.

Regulating Local Atomic Environment around Vacancies for Efficient Hydrogen Evolution

Defect engineering is essential for the development of efficient electrocatalysts at the atomic level. While most work has focused on various vacancies as effective catalytic modulators, little attention has been paid to the relation between the local atomic environment of vacancies and catalytic activities. To face this challenge, we report a facile synthetic approach to manipulate the local atomic environments of vacancies in MoS2 with tunable Mo-to-S ratios. Our studies indicate that the MoS2 with more Mo terminated vacancies exhibits better hydrogen evolution reaction (HER) performance than MoS2 with S terminated vacancies and defect-free MoS2. The improved performance originates from the adjustable orbital orientation and distribution, which is beneficial for regulating H adsorption and eventually boosting the intrinsic per-site activity. This work uncovers the underlying essence of the local atomic environment of vacancies on catalysis and provides a significant extension of defect engineering for the rational design of transition metal dichalcogenides (TMDs) catalysts and beyond.

Ultra-small Mo-Pt subnanoparticles enable CO2 hydrogenation at room temperature and atmospheric pressure

We present a partially-oxidised bimetallic Mo-Pt subnanoparticle (Mo4Pt8Ox) enabling thermally-driven CO2 hydrogenation to CO at room temperature and atmospheric pressure. A mechanistic study explained the full catalytic cycle of the reaction from CO2 activation to catalyst reactivation. DFT calculations revealed that alloying with Mo lowers the activation barrier by weakening the CO adsorption. This finding could be a first step for low-energy CO2 conversion.

Bimetallic Sites for Catalysis: From Binuclear Metal Sites to Bimetallic Nanoclusters and Nanoparticles

Heterogeneous bimetallic catalysts have broad applications in industrial processes, but achieving a fundamental understanding on the nature of the active sites in bimetallic catalysts at the atomic and molecular level is very challenging due to the structural complexity of the bimetallic catalysts. Comparing the structural features and the catalytic performances of different bimetallic entities will favor the formation of a unified understanding of the structure-reactivity relationships in heterogeneous bimetallic catalysts and thereby facilitate the upgrading of the current bimetallic catalysts. In this review, we will discuss the geometric and electronic structures of three representative types of bimetallic catalysts (bimetallic binuclear sites, bimetallic nanoclusters, and nanoparticles) and then summarize the synthesis methodologies and characterization techniques for different bimetallic entities, with emphasis on the recent progress made in the past decade. The catalytic applications of supported bimetallic binuclear sites, bimetallic nanoclusters, and nanoparticles for a series of important reactions are discussed. Finally, we will discuss the future research directions of catalysis based on supported bimetallic catalysts and, more generally, the prospective developments of heterogeneous catalysis in both fundamental research and practical applications.