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.
Abstract
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.
We report an Ag1 single‐atom catalyst (Ag1/MnO2), which was synthesized from thermal transformation of Ag nanoparticles (NPs) and surface reconstruction of MnO2. The evolution process of Ag NPs to ...single atoms is firstly revealed by various techniques, including in situ ETEM, in situ XRD and DFT calculations. The temperature‐induced surface reconstruction process from the MnO2 (211) to (310) lattice plane is critical to firmly confine the existing surface of Ag single atoms; that is, the thermal treatment and surface reconstruction of MnO2 is the driving force for the formation of single Ag atoms. The as‐obtained Ag1/MnO2 achieved 95.7 % Faradic efficiency at −0.85 V vs. RHE, and coupled with long‐term stability for electrochemical CO2 reduction reaction (CO2RR). DFT calculations indicated single Ag sites possessed high electronic density close to Fermi Level and could act exclusively as the active sites in the CO2RR. As a result, the Ag1/MnO2 catalyst demonstrated remarkable performance for the CO2RR, far surpassing the conventional Ag nanosized catalyst (AgNP/MnO2) and other reported Ag‐based catalysts.
Silver nanoparticles converted into single atoms bring about a significant improvement in electrocatalytic CO2 reduction with a 95.7 % faradic efficiency for CO production.
Selective cleavage of C–C linkages is the key and a challenge for lignin degradation to harvest value-added aromatic compounds. To this end, electrocatalytic oxidation presents a promising technique ...by virtue of mild reaction conditions and strong sustainability. However, the existing electrocatalysts (traditional bulk metal and metal oxides) for C–C bond oxidative cleavage suffer from poor selectivity and low product yields. We show for the first time that atomically dispersed Pt–N3C1 sites planted on nitrogen-doped carbon nanotubes (Pt1/N-CNTs), constructed via a stepwise polymerization–carbonization–electrostatic adsorption strategy, are highly active and selective toward Cα–Cβ bond cleavage in β-O-4 model compounds under ambient conditions. Pt1/N-CNTs exhibits 99% substrate conversion with 81% yield of benzaldehyde, which is exceptional and unprecedented compared with previously reported electrocatalysts. Moreover, Pt1/N-CNTs using only 0.41 wt % Pt achieved a much higher benzaldehyde yield than those of the state-of-the-art bulk Pt electrode (100 wt % Pt) and commercial Pt/C catalyst (20 wt % Pt). Systematic experimental investigation together with density functional theory (DFT) calculation suggests that the superior performance of Pt1/N-CNTs arises from the atomically dispersed Pt–N3C1 sites facilitating the formation of a key Cβ radical intermediate, further inducing a radical/radical cross-coupling path to break the Cα–Cβ bond. This work opens up opportunities in lignin valorization via a green and sustainable electrochemical route with ultralow noble metal usage.
A series of 2-3 nm Pt-Sn bimetallic nanoparticles with different Pt-Sn coordination numbers were synthesized by a stepwise approach including electrostatic adsorption and temperature-programmed ...reduction of metal precursors on the SiO2 support. In situ synchrotron XRD and XAFS demonstrated a highly ordered hexagonal Pt1Sn1 intermetallic shell on Pt nanoparticles. The turnover rates (TORs), propylene selectivity and stability of these bimetallic catalysts significantly surpass those of the monometallic Pt catalyst for propane dehydrogenation. At the same time, TORs increase with increasing Pt-Sn coordination number, whereas propylene selectivity is not significantly influenced by the Pt-Sn coordination number. Combined with experiments and theoretical calculations, the high propylene selectivity of the Pt-Sn bimetallic nanoparticles is attributed to the geometric effects of Sn that reduce the Pt ensembles, and the high TORs are due to the electronic effects that weaken Pt-hydrocarbon chemisorption energies.
The reaction system of hydrogen peroxide (H
O
) 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
substrate, POD is enhanced while HORAC is inhibited, which is further confirmed by density functional theory (DFT) calculations. Cu-CeO
+ H
O
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.
With the surge of shale gas, propane dehydrogenation becomes increasingly important to synthesize propylene. Herein, a new type of ordered PtSnZn intermetallic clusters (∼0.9 nm) supported on Al
2
O
...3
was synthesized by a stepwise approach including electrostatic adsorption and temperature-programmed reduction. The structure of the PtSnZn clusters results from a kinetically controlled process, and Pt atoms in the PtSnZn clusters are well isolated by Sn and Zn with Pt−Sn and Pt−Zn pairs. The PtSnZn/Al
2
O
3
catalyst exhibits excellent catalytic performance for propane dehydrogenation, which achieves ∼100% propylene selectivity and keeps a high propane conversion (>40%) during stability testing. The catalytic performance of PtSnZn/Al
2
O
3
is also significantly higher than that of Pt/Al
2
O
3
, PtSn/Al
2
O
3
, and PtZn/Al
2
O
3
. Experiments and theoretical calculations indicate that the Sn 5p and Zn 4s orbitals are hybridized with Pt 5d by forming Pt−Sn and Pt−Zn pairs, which leads to the d band center of Pt deviating from Fermi level (−2.81 eV). The shift of the Pt d band center significantly decreases the adsorption energy of propylene and prohibits further dehydrogenation, resulting in high propylene selectivity and stability.
Nonequilibrium intermetallic phases in the nanoscale were realized by diffusion-controlled solid-state transformation, forming SiO2 supported NPs with Pd core and a CsCl type Pd1M1 shell, where M is ...Sn or Sb. The core–shell geometry is identified from scanning transmission electron microscopy and infrared spectroscopy and the crystal structure is confirmed from in situ synchrotron X-ray diffraction and X-ray absorption spectroscopy. The highly symmetric Pd1M1 intermetallic phase has not been reported previously and contains catalytic ensembles with high selectivity toward dehydrogenation of propane. The kinetically limited solid-state reaction is generally applicable to nanoparticle synthesis and could produce materials with desired structures and properties beyond conventional structural limits
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.
PDF
