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In recent decades, the environmental protection and long-term sustainability have become the focus of attention due to the increasing pollution generated by the intense industrialization. To overcome these issues, environmental catalysis has increasingly been used to solve the negative impact of pollutants emission on the global environment and human health. Supported platinum-metal-group (PGM) materials are commonly utilized as the state-of-the-art catalysts to eliminate gaseous pollutants but large quantities of PGMs are required. By comparison, single-atom site catalysts (SACs) have attracted much attention in catalysis owing to their 100% atom efficiency and unique catalytic performances towards various reactions. Over the past decade, we have witnessed burgeoning interests of SACs in heterogeneous catalysis. However, to the best of our knowledge, the systematic summary and analysis of SACs in catalytic elimination of environmental pollutants has not yet been reported. In this paper, we summarize and discuss the environmental catalysis applications of SACs. Particular focus was paid to automotive and stationary emission control, including model reaction (CO oxidation, NO reduction and hydrocarbon oxidation), overall reaction (three-way catalytic and diesel oxidation reaction), elimination of volatile organic compounds (formaldehyde, benzene, and toluene), and removal/decomposition of other pollutants (Hg 0 and SO 3 ). Perspectives related to further challenges, directions and design strategies of single-atom site catalysts in environmental catalysis were also provided.

Heterojunctions modulated internal electric field (IEF) usually result in suboptimal efficiencies in carrier separation and utilization because of the narrow IEF distribution and long migration paths of photocarriers. In this work, we report distinctive bismuth oxyhydroxide compound nanorods (denoted as BOH NRs) featuring surface-exposed open channels and a simple chemical composition; by simply modifying the bulk anion layers to overcome the limitations of heterojunctions, the bulk IEF could be readily modulated. Benefiting from the unique crystal structure and the localization of valence electrons, the bulk IEF intensity increases with the atomic number of introduced halide anions. Therefore, A low exchange ratio (~10%) with halide anions (I – , Br – , Cl – ) gives rise to a prominent elevation in carrier separation efficiency and better photocatalytic performance for benzylamine coupling oxidation. Here, our work offers new insights into the design and optimization of semiconductor photocatalysts. Research on the bulk internal electric field (IEF) regulation is significant for designing high-efficiency photocatalysts. Here, the authors report distinctive bismuth oxyhydroxide nanorods photocatalyst and increase the bulk IEF intensity by halogen ions exchange.

The reaction system of hydrogen peroxide (H 2 O 2 ) catalyzed by nanozyme has a broad prospect in antibacterial treatment. However, the complex catalytic activities of nanozymes lead to multiple pathways reacting in parallel, causing uncertain antibacterial results. New approach to effectively regulate the multiple catalytic activities of nanozyme is in urgent need. Herein, Cu single site is modified on nanoceria with various catalytic activities, such as peroxidase-like activity (POD) and hydroxyl radical antioxidant capacity (HORAC). Benefiting from the interaction between coordinated Cu and CeO 2 substrate, POD is enhanced while HORAC is inhibited, which is further confirmed by density functional theory (DFT) calculations. Cu-CeO 2  + H 2 O 2 system shows good antibacterial properties both in vitro and in vivo. In this work, the strategy based on the interaction between coordinated metal and carrier provides a general clue for optimizing the complex activities of nanozymes. Nanozymes used for antibacterial therapy conventionally have complex catalytic activities that cause multiple pathways in parallel and unwanted outcome. Here, the authors report a Cu-CeO 2 single site nanozyme in which Cu single site modification can enhance the peroxidase-like activity and inhibit the hydroxyl radical antioxidant capacity of CeO 2 to optimise the antibacterial effects.

Single-atom catalysts (SACs) have emerged as highly promising catalytic materials for the hydrogen evolution reaction (HER), attributed to their maximal atomic utilization efficiency and unique electronic configurations. Many structure parameters can influence the catalytic performance of SACs for HER, and the intrinsic advantages of SACs for HER still need to be summarized. This review systematically summarizes recent advances in SACs for HER. It discusses various types of SACs (including those based on Pt, Co, Ru, Ni, Cu, and other metals) applied in HER, and elaborates the critical factors influencing catalytic performance—specifically, the supports, coordination environments, and synergistic effects of these SACs. Furthermore, current research challenges and future perspectives in this rapidly developing field are also outlined.

Prussian blue analogs (PBAs), as a classical kind of microporous materials, have attracted substantial interests considering their well-defined framework structures, unique physicochemical properties and low cost. However, PBAs typically adopt cubic structure that features small pore size and low specific surface area, which greatly limits their practical applications in various fields ranging from gas adsorption/separation to energy conversion/storage and biomedical treatments. Here we report the facile and general synthesis of unconventional hexagonal open PBA structures. The obtained hexagonal copper hexacyanocobaltate PBA prisms (H-CuCo) demonstrate large pore size and specific surface area of 12.32 Å and 1273 m 2 g − 1 , respectively, well exceeding those (5.48 Å and 443 m 2 g − 1 ) of traditional cubic CuCo PBA cubes (C-CuCo). Significantly, H-CuCo exhibits much superior gas uptake capacity over C-CuCo toward carbon dioxide and small hydrocarbon molecules. Mechanism studies reveal that unsaturated Cu sites with planar quadrilateral configurations in H-CuCo enhance the gas adsorption performance. The unconventional hexagonal phase CuCo PBA with open structure, large pore size, and high specific surface area is synthesized, and it delivers much better small molecular gas adsorption performance than the traditional cubic counterpart.

Chemocatalytic transformation of lignocellulosic biomass to value-added chemicals has attracted global interest in order to build up sustainable societies. Cellulose, the first most abundant constituent of lignocellulosic biomass, has received extensive attention for its comprehensive utilization of resource, such as its catalytic conversion into high value-added chemicals and fuels (e.g., HMF, DMF, and isosorbide). However, the low reactivity of cellulose has prevented its use in chemical industry due to stable chemical structure and poor solubility in common solvents over the cellulose. Recently, homogeneous or heterogeneous catalysis for the conversion of cellulose has been expected to overcome this issue, because various types of pretreatment and homogeneous or heterogeneous catalysts can be designed and applied in a wide range of reaction conditions. In this review, we show the present situation and perspective of homogeneous or heterogeneous catalysis for the direct conversion of cellulose into useful platform chemicals.

The skyrocketing production of lithium-ion batteries (LIBs) for electric vehicles portends that tremendous numbers of used LIBs will be generated. However, the recycling of used LIBs is limited by the complicated separation processes of traditional pyrometallurgy and hydrometallurgy methods. Here, we applied a rapid thermal radiation method to convert spent LiNi1-x-yMnₓCoyO₂ (NMC) cathodes from used LIBs into highly efficient NiMnCo-based catalysts for zinc-air batteries (ZABs) through acid leaching and radiative heating processes, which avoids sophisticated separation of different metals and can synthesize the catalysts rapidly. The prepared NiMnCo-activated carbon (NiMnCo-AC) catalyst presents a unique core-shell structure, with face-centered cubic Ni in the core and spinel NiMnCoO₄ in the shell, which redistributes the electronic structure of the NiMnCoO₄ shell to decrease the energy barrier for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) processes and ensures high electrocatalytic activities. The NiMnCo-AC catalyst in ZABs as cathode materials exhibits a high power density of 187.7 mW cm−2, low voltage gap of 0.72 V at the initial three cycles, and long cycling duration of 200 h at the current density of 10 mA cm−2. This work provides a promising strategy to recycle spent LIBs to highly efficient catalysts for ZABs.

In this study, Pd-Mg(Al)-LDH/γ-Al 2 O 3 and Pd-Mg(Al)Zr-LDH/γ-Al 2 O 3 precursors were synthesized by impregnating Na 2 PdCl 4 on Mg(Al)-LDH/γ-Al 2 O 3 and Mg(Al)Zr-LDH/γ-Al 2 O 3 , and then the precursors were calcinated and reduced to obtain Pd-Mg(Al)-MMO/γ-Al 2 O 3 and Pd-Mg(Al)Zr-MMO/γ-Al 2 O 3 catalysts. Compared with Pd/γ-Al 2 O 3 catalyst, the hydrogenation efficiency of Pd-Mg(Al)-MMO/γ-Al 2 O 3 and Pd-Mg(Al)Zr-MMO/γ-Al 2 O 3 increased by 15.7% and 24.0%, respectively. Moreover, the stability of Pd-Mg(Al)Zr-MMO/γ-Al 2 O 3 catalyst was also higher than that of Pd/γ-Al 2 O 3 . After four runs, the hydrogenation efficiency of Pd/γ-Al 2 O 3 decreased from 12.1 to 10.0 g/L, while that of Pd-Mg(Al)Zr-MMO/γ-Al 2 O 3 decreased from 15.0 to 14.3 g/L. The active aquinones selectivities of all catalysts were almost 99%. The structures of the catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N 2 adsorption–desorption, inductively coupled plasma-atomic emission spectrometry (ICP-AES), CO chemisorption analysis, transmission electron microscopy (TEM), temperature-programmed reduction with hydrogen (H 2 -TPR), and X-ray photoelectron spectroscopy (XPS). The results indicate that the improved catalytic performance is attributed to the stronger interaction between Pd and Mg(Al)Zr-MMO/γ-Al 2 O 3 , smaller Pd particle size and higher Pd dispersion. This work develops an effective method to synthesize highly dispersed Pd nanoparticles based on the layered double hydroxides (LDHs) precursor.

Non-Pt or low-Pt catalysts capable for stable generation of hydrogen via water electrolysis at an industrial level of current density are highly demanded. Construction of strong metal-support connection is beneficial to improve the performance stability of electrocatalysts. Here we employed highly defective N-doped carbon nanotubes (d-N-CNT) as the support to achieve uniform and firm anchoring of Ru clusters (~ 1.9 nm) via a thermal-shock strategy. The as-prepared Ru/d-N-CNT catalyst shows excellent catalytic activity for hydrogen evolution reaction (HER) in alkaline media and requires an overpotential (η) of 12 mV at 10 mA·cm −2 and 116 mV at 200 mA·cm −2 with a Ru loading of 0.025 mg·cm −2 . Impressively, Ru/d-N-CNT presents robust stability for HER at both low current density (stable for at least 1000 h at 10 mA·cm −2 ) and the industrial level of current density (stable for at least 100 h at 1000 mA·cm −2 ), remarkably outperforming commercial Pt/C and Ru/C. The highly defective nature of the N-CNT support endowed the as-prepared Ru/d-N-CNT catalyst with strong metal–support adhesion that efficiently suppressed agglomeration as well as obscission of Ru clusters. Meanwhile, the rich defects increased the surface energy of the N-CNT support and resulted in improved hydrophilicity as evidenced by the liquid contact angle measurement and the bubble evolution process, which also played an important role in stabilizing the HER performance especially at large current density.

Given the high energy density and eco-friendly characteristics, lithium-carbon dioxide (Li-CO₂) batteries have been considered to be a next-generation energy technology to promote carbon neutral and space exploration. However, Li-CO₂ batteries suffer from sluggish reaction kinetics, causing large overpotential and poor energy efficiency. Here, we observe enhanced reaction kinetics in aprotic Li-CO₂ batteries with unconventional phase 4H/face-centered cubic (fcc) iridium (Ir) nanostructures grown on gold template. Significantly, 4H/fcc Ir exhibits superior electrochemical performance over fcc Ir in facilitating the round-trip reaction kinetics of Li⁺-mediated CO₂ reduction and evolution, achieving a low charge plateau below 3.61 V and high energy efficiency of 83.8%. Ex situ/in situ studies and theoretical calculations reveal that the boosted reaction kinetics arises from the highly reversible generation of amorphous/low-crystalline discharge products on 4H/fcc Ir via the Ir-O coupling. The demonstration of flexible Li-CO₂ pouch cells with 4H/fcc Ir suggests the feasibility of using unconventional phase nanomaterials in practical scenarios.