scholarly journals Regulating the coordination structure of single-atom Fe-NxCy catalytic sites for benzene oxidation

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yuan Pan ◽  
Yinjuan Chen ◽  
Konglin Wu ◽  
Zheng Chen ◽  
Shoujie Liu ◽  
...  
Keyword(s):  
Active Sites ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Single Atom ◽  
Coordination Pattern ◽  
Benzene Oxidation ◽  
Coordination Environment ◽  
Catalytic Sites ◽  
Coordination Effect ◽  
Oxidative Species

Abstract Atomically dispersed metal-N-C structures are efficient active sites for catalyzing benzene oxidation reaction (BOR). However, the roles of N and C atoms are still unclear. We report a polymerization-regulated pyrolysis strategy for synthesizing single-atom Fe-based catalysts, and present a systematic study on the coordination effect of Fe-NxCy catalytic sites in BOR. The special coordination environment of single-atom Fe sites brings a surprising discovery: Fe atoms anchored by four-coordinating N atoms exhibit the highest BOR performance with benzene conversion of 78.4% and phenol selectivity of 100%. Upon replacing coordinated N atoms by one or two C atoms, the BOR activities decrease gradually. Theoretical calculations demonstrate the coordination pattern influences not only the structure and electronic features, but also the catalytic reaction pathway and the formation of key oxidative species. The increase of Fe-N coordination number facilitates the generation and activation of the crucial intermediate O=Fe=O species, thereby enhancing the BOR activity.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

scholarly journals Platinum–copper single atom alloy catalysts with high performance towards glycerol hydrogenolysis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xi Zhang ◽  
Guoqing Cui ◽  
Haisong Feng ◽  
Lifang Chen ◽  
Hui Wang ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Value Added ◽  
Catalytic Performance ◽  
Single Atom ◽  
Glycerol Hydrogenolysis ◽  
Single Atom Alloy

AbstractSelective hydrogenolysis of biomass-derived glycerol to propanediol is an important reaction to produce high value-added chemicals but remains a big challenge. Herein we report a PtCu single atom alloy (SAA) catalyst with single Pt atom dispersed on Cu nanoclusters, which exhibits dramatically boosted catalytic performance (yield: 98.8%) towards glycerol hydrogenolysis to 1,2-propanediol. Remarkably, the turnover frequency reaches up to 2.6 × 103 molglycerol·molPtCu–SAA−1·h−1, which is to our knowledge the largest value among reported heterogeneous metal catalysts. Both in situ experimental studies and theoretical calculations verify interface sites of PtCu–SAA serve as intrinsic active sites, in which the single Pt atom facilitates the breakage of central C–H bond whilst the terminal C–O bond undergoes dissociation adsorption on adjacent Cu atom. This interfacial synergistic catalysis based on PtCu–SAA changes the reaction pathway with a decreased activation energy, which can be extended to other noble metal alloy systems.

scholarly journals Dynamic Structural Changes in Nickel Single-Atom Catalysts During Electrochemical Reduction of CO2 to CO

2021 ◽  
Author(s):  
Bingbao Mei ◽  
Changzhi Ai ◽  
Lushan Ma ◽  
Cong Liu ◽  
Shuai Yang ◽  
...  
Keyword(s):  
Active Sites ◽  
Structural Changes ◽  
Theoretical Calculations ◽  
Reduction Reaction ◽  
Single Atom ◽  
Structure Evolution ◽  
Potential Range ◽  
Dynamic Configuration ◽  
Carbon Abatement ◽  
Reduction Of Co2

Abstract Electrochemical CO2 reduction reaction (ECO2RR) is an important route for global carbon abatement. However, a comprehensive picture of the structure evolution of metal active sites is currently lacked in ECO2RR. Here, we present the first full view of Ni single-atom catalyst for ECO2RR over a broad potential range. Comprehensive X-ray absorption spectroscopy (XAS) analyses confirmed the Ni coordinated with pyrrole nitrogen in the form of Ni-N4 attached with an axial O2 ligand. Operando XAS revealed the precise structure of the Ni single-atom catalyst that dynamically changes with the shift of applied potentials. Such changes ultimately contributed to the CO selectivity variation ranging from 20%-99%. Interestingly, the Ni center was found to move toward the N4 plane during the ECO2RR, which played a crucial role of reaching near-unity CO selectivity. Together with theoretical calculations, a clear quantitative correlation between the dynamic configuration and the catalytic properties was established.

scholarly journals Single-Atom Pd–N3 Sites on Carbon-Deficient g-C3N4 for Photocatalytic H2 Evolution

2021 ◽  
Author(s):  
Guimei Liu ◽  
Haiqin Lv ◽  
Yubin Zeng ◽  
Mingzhe Yuan ◽  
Qingguo Meng ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Active Sites ◽  
Charge Carriers ◽  
Single Atom ◽  
H2 Evolution ◽  
Environment Friendly ◽  
Coordination Environment ◽  
Highly Active ◽  
Excellent Photocatalytic Activity ◽  
New Strategy

AbstractPhotocatalytic hydrogen evolution is an attractive field for future environment-friendly energy. However, fast recombination of photogenerated charges severely inhibits hydrogen efficiency. Single-atom cocatalysts such as Pt have emerged as an effective method to enhance the photocatalytic activity by introduction of active sites and boosting charge separation with low-coordination environment. Herein, we demonstrated a new strategy to develop a highly active Pd single atom in carbon-deficient g-C3N4 with a unique coordination. The single-atom Pd–N3 sites constructed by oil bath heating and photoreduction process were confirmed by HADDF-STEM and XPS measurements. Introduction of single-atom Pd greatly improved the separation and transportation of charge carriers, leading to a longer lifespan for consequent reactions. The obtained single-atom Pd loaded on the carbon-deficient g–C3N4 showed excellent photocatalytic activity in hydrogen production with about 24 and 4 times higher activity than that of g–C3N4 and nano-sized Pd on the same support, respectively. This work provides a new insight on the design of single-atom catalyst.

scholarly journals Directing reaction pathways via in situ control of active site geometries in PdAu single-atom alloy catalysts

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mengyao Ouyang ◽  
Konstantinos G. Papanikolaou ◽  
Alexey Boubnov ◽  
Adam S. Hoffman ◽  
Georgios Giannakakis ◽  
...  
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Bimetallic Catalyst ◽  
Theoretical Calculations ◽  
Atomic Scale ◽  
Single Atom ◽  
In Situ Control ◽  
Single Atom Alloy

AbstractThe atomic scale structure of the active sites in heterogeneous catalysts is central to their reactivity and selectivity. Therefore, understanding active site stability and evolution under different reaction conditions is key to the design of efficient and robust catalysts. Herein we describe theoretical calculations which predict that carbon monoxide can be used to stabilize different active site geometries in bimetallic alloys and then demonstrate experimentally that the same PdAu bimetallic catalyst can be transitioned between a single-atom alloy and a Pd cluster phase. Each state of the catalyst exhibits distinct selectivity for the dehydrogenation of ethanol reaction with the single-atom alloy phase exhibiting high selectivity to acetaldehyde and hydrogen versus a range of products from Pd clusters. First-principles based Monte Carlo calculations explain the origin of this active site ensemble size tuning effect, and this work serves as a demonstration of what should be a general phenomenon that enables in situ control over catalyst selectivity.

scholarly journals Secondary-Atom-Doping Enables Robust Fe–N–C Single-Atom Catalysts with Enhanced Oxygen Reduction Reaction

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Xin Luo ◽  
Xiaoqian Wei ◽  
Hengjia Wang ◽  
Wenling Gu ◽  
Takuma Kaneko ◽  
...  
Keyword(s):  
Active Sites ◽  
Reduction Reaction ◽  
Single Atom ◽  
General Strategy ◽  
Carbon Supports ◽  
Coordination Environment ◽  
Energy Devices ◽  
Highly Active ◽  
Half Wave ◽  
Secondary Doping

AbstractSingle-atom catalysts (SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis. However, a large room for improving their activity and durability remains. Herein, we construct atomically dispersed Fe sites in N-doped carbon supports by secondary-atom-doped strategy. Upon the secondary doping, the density and coordination environment of active sites can be efficiently tuned, enabling the simultaneous improvement in the number and reactivity of the active site. Besides, structure optimizations in terms of the enlarged surface area and improved hydrophilicity can be achieved simultaneously. Due to the beneficial microstructure and abundant highly active FeN5 moieties resulting from the secondary doping, the resultant catalyst exhibits an admirable half-wave potential of 0.81 V versus 0.83 V for Pt/C and much better stability than Pt/C in acidic media. This work would offer a general strategy for the design and preparation of highly active SACs for electrochemical energy devices.

Reconstructing the Coordination Environment of Platinum Single-Atom Active Sites for Boosting Oxygen Reduction Reaction

ACS Catalysis ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 466-475
Author(s):  
Jing Liu ◽  
Junu Bak ◽  
Jeonghan Roh ◽  
Kug-Seung Lee ◽  
Ara Cho ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Single Atom ◽  
Coordination Environment

scholarly journals Single-atom nanozymes

2019 ◽  
Vol 5 (5) ◽  
pp. eaav5490 ◽  
Author(s):  
Liang Huang ◽  
Jinxing Chen ◽  
Linfeng Gan ◽  
Jin Wang ◽  
Shaojun Dong
Keyword(s):  
Active Sites ◽  
Synergistic Effects ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Size Composition ◽  
Underlying Mechanism ◽  
Catalytic Performance ◽  
Axial Ligand ◽  
Single Atom ◽  
Active Centers

Conventional nanozyme technologies face formidable challenges of intricate size-, composition-, and facet-dependent catalysis and inherently low active site density. We discovered a new class of single-atom nanozymes with atomically dispersed enzyme-like active sites in nanomaterials, which significantly enhanced catalytic performance, and uncovered the underlying mechanism. With oxidase catalysis as a model reaction, experimental studies and theoretical calculations revealed that single-atom nanozymes with carbon nanoframe–confined FeN5 active centers (FeN5 SA/CNF) catalytically behaved like the axial ligand–coordinated heme of cytochrome P450. The definite active moieties and crucial synergistic effects endow FeN5 SA/CNF with a clear electron push-effect mechanism, as well as the highest oxidase-like activity among other nanozymes (the rate constant is 70 times higher than that of commercial Pt/C) and versatile antibacterial applications. These suggest that the single-atom nanozymes have great potential to become the next-generation nanozymes.

scholarly journals Atomically Dispersed Catalytic Sites: A New Frontier for Cocatalyst/Photocatalyst Composites toward Sustainable Fuel and Chemical Production

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1168
Author(s):  
Shuping Zhang ◽  
Bing Bai ◽  
Jia Liu ◽  
Jiatao Zhang
Keyword(s):  
Water Splitting ◽  
Active Sites ◽  
Photogenerated Electron ◽  
Photon Absorption ◽  
Single Atom ◽  
Photocatalytic Water Splitting ◽  
Support Materials ◽  
New Frontier ◽  
Catalytic Sites ◽  
The Future

Photocatalysis delivers a promising pathway toward the clean and sustainable energy supply of the future. However, the inefficiency of photon absorption, rapid recombination of photogenerated electron-hole pairs, and especially the limited active sites for catalytic reactions result in unsatisfactory performances of the photocatalytic materials. Single-atom photocatalysts (SAPCs), in which metal atoms are individually isolated and stably anchored on support materials, allow for maximum atom utilization and possess distinct photocatalytic properties due to the unique geometric and electronic features of the unsaturated catalytic sites. Very recently, constructing SAPCs has emerged as a new avenue for promoting the efficiency of sustainable production of fuels and chemicals via photocatalysis. In this review, we summarize the recent development of SAPCs as a new frontier for cocatalyst/photocatalyst composites in photocatalytic water splitting. This begins with an introduction on the typical structures of SAPCs, followed by a detailed discussion on the synthetic strategies that are applicable to SAPCs. Thereafter, the promising applications of SAPCs to boost photocatalytic water splitting are outlined. Finally, the challenges and prospects for the future development of SAPCs are summarized.

scholarly journals Origin of enhanced water oxidation activity in an iridium single atom anchored on NiFe oxyhydroxide catalyst

2021 ◽  
Vol 118 (36) ◽  
pp. e2101817118
Author(s):  
Xueli Zheng ◽  
Jing Tang ◽  
Alessandro Gallo ◽  
Jose A. Garrido Torres ◽  
Xiaoyun Yu ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Active Sites ◽  
High Performance ◽  
Operating Conditions ◽  
Utilization Efficiency ◽  
Oxidation Catalyst ◽  
Single Atom ◽  
Photochemical Reduction ◽  
Oxidation Activity ◽  
Coordination Environment

The efficiency of the synthesis of renewable fuels and feedstocks from electrical sources is limited, at present, by the sluggish water oxidation reaction. Single-atom catalysts (SACs) with a controllable coordination environment and exceptional atom utilization efficiency open new paradigms toward designing high-performance water oxidation catalysts. Here, using operando X-ray absorption spectroscopy measurements with calculations of spectra and electrochemical activity, we demonstrate that the origin of water oxidation activity of IrNiFe SACs is the presence of highly oxidized Ir single atom (Ir5.3+) in the NiFe oxyhydroxide under operating conditions. We show that the optimal water oxidation catalyst could be achieved by systematically increasing the oxidation state and modulating the coordination environment of the Ir active sites anchored atop the NiFe oxyhydroxide layers. Based on the proposed mechanism, we have successfully anchored Ir single-atom sites on NiFe oxyhydroxides (Ir0.1/Ni9Fe SAC) via a unique in situ cryogenic–photochemical reduction method that delivers an overpotential of 183 mV at 10 mA ⋅ cm−2 and retains its performance following 100 h of operation in 1 M KOH electrolyte, outperforming the reported catalysts and the commercial IrO2 catalysts. These findings open the avenue toward an atomic-level understanding of the oxygen evolution of catalytic centers under in operando conditions.

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