Exceeding the volcano relationship in oxygen reduction/evolution reactions using single-atom-based catalysts with dual-active-sites

2020 ◽  
Vol 8 (20) ◽  
pp. 10193-10198 ◽  
Author(s):  
Xiyu Li ◽  
Sai Duan ◽  
Edward Sharman ◽  
Yuan Zhao ◽  
Li Yang ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Site ◽  
Active Sites ◽  
Single Atom ◽  
Orr Activity

Both a linear OER activity trend that reaches an ideal 0 V overpotential and a new volcano ORR activity trend with the volcano apex around ideal 1.23 V limiting potential are associated with our dual-active-site designs.

Active site engineering of atomically dispersed transition metal-heteroatom-carbon catalysts for oxygen reduction

2021 ◽  
Author(s):  
Jiawei Zhu ◽  
Shichun Mu
Keyword(s):  
Transition Metal ◽  
Oxygen Reduction ◽  
Active Site ◽  
Catalytic Reactions ◽  
Single Atom ◽  
Carbon Catalysts

Owing to the advantage of atomic utilization, the single-atom catalyst has attracted much attention and been employed in multifarious catalytic reactions. Their definite site configuration is favorable for exploring the...

scholarly journals Substrate strain tunes operando geometric distortion and oxygen reduction activity of CuN2C2 single-atom sites

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Guokang Han ◽  
Xue Zhang ◽  
Wei Liu ◽  
Qinghua Zhang ◽  
Zhiqiang Wang ◽  
...  
Keyword(s):  
Structure Function ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Geometric Distortion ◽  
Single Atom ◽  
Reduction Activity ◽  
Activity Promotion ◽  
Structure Function Relationship ◽  
Substrate Strain ◽  
Function Relationship

AbstractSingle-atom catalysts are becoming increasingly significant to numerous energy conversion reactions. However, their rational design and construction remain quite challenging due to the poorly understood structure–function relationship. Here we demonstrate the dynamic behavior of CuN2C2 site during operando oxygen reduction reaction, revealing a substrate-strain tuned geometry distortion of active sites and its correlation with the activity. Our best CuN2C2 site, on carbon nanotube with 8 nm diameter, delivers a sixfold activity promotion relative to graphene. Density functional theory and X-ray absorption spectroscopy reveal that reasonable substrate strain allows the optimized distortion, where Cu bonds strongly with the oxygen species while maintaining intimate coordination with C/N atoms. The optimized distortion facilitates the electron transfer from Cu to the adsorbed O, greatly boosting the oxygen reduction activity. This work uncovers the structure–function relationship of single-atom catalysts in terms of carbon substrate, and provides guidance to their future design and activity promotion.

Highly Efficient Low-Pt-Based Electrocatalysts with Pt Single-Atom Active Sites for Oxygen Reduction Reaction

2020 ◽  
Vol MA2020-01 (38) ◽  
pp. 1688-1688
Author(s):  
Jing Liu ◽  
JeongHan Roh ◽  
DongHoon Song ◽  
Junu Bak ◽  
Hyo-Jong Kim ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Single Atom ◽  
Highly Efficient

scholarly journals Warped graphitic layers generated by oxidation of fullerene extraction residue and its oxygen reduction catalytic activity

2019 ◽  
Vol 10 ◽  
pp. 1391-1400 ◽  
Author(s):  
Machiko Takigami ◽  
Rieko Kobayashi ◽  
Takafumi Ishii ◽  
Yasuo Imashiro ◽  
Jun-ichi Ozaki
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Oxidation Time ◽  
Pt Catalyst ◽  
Oxidation Treatment ◽  
Orr Activity ◽  
Temperature Programmed ◽  
Carbon Catalysts

Carbon-based oxygen reduction reaction (ORR) catalysts are regarded as a promising candidate to replace the currently used Pt catalyst in polymer electrolyte fuel cells (PEFCs); however, the active sites remain under discussion. We predicted that warped graphitic layers (WGLs) are responsible for the ORR catalytic activity in some carbon catalysts (i.e., carbon alloy catalysts (CACs)). To prove our assumption, we needed to use WGLs consisting of carbon materials, but without any extrinsic catalytic elements, such as nitrogen, iron, or cobalt, which effectively enhance ORR activity. The present study employed a fullerene extraction residue as a starting material to construct WGLs. The oxidation of the material at 600 °C exposed the WGLs by removing the surrounding amorphous moieties. Transmission electron microscopy (TEM) observations revealed the formation of WGLs by oxidation treatment at 600 °C in an O2/N2 stream. Extending the oxidation time increased the purity of the WGL phase, but also simultaneously increased the concentration of oxygen-containing surface functional groups as monitored by temperature programmed desorption (TPD). The specific ORR activity increased with oxidation up to 1 h and then decreased with the intensive oxidation treatment. Correlations between the specific ORR activity and other parameters confirmed that the development of the WGL and the increase in the O/C ratio are the competing factors determining specific ORR activity. These results explain the maximum specific ORR activity after 1 h of oxidation time. WGLs were found to lower the heat of adsorption for O2 and to increase the occurrence of heterogeneous electron transfer.

scholarly journals Migration-Prevention Strategy to Fabricate Single-Atom Fe Implanted N-Doped Porous Carbons for Efficient Oxygen Reduction

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Dong-Li Meng ◽  
Chun-Hui Chen ◽  
Jun-Dong Yi ◽  
Qiao Wu ◽  
Jun Liang ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Carbonaceous Material ◽  
Nitrogen Sources ◽  
Reduction Reaction ◽  
Prevention Strategy ◽  
Alkaline Media ◽  
Single Atom ◽  
Porous Carbons ◽  
Iron Species

It is highly desired but challenging to achieve highly active single-atom Fe sites from iron-based metal-organic frameworks (MOFs) for efficient oxygen reduction reaction (ORR) due to the easy aggregation of iron species and formation of the inactive Fe-based particles during pyrolysis. Herein, a facile migration-prevention strategy is developed involving the incorporation of polyaniline (PANI) into the pores of iron porphyrinic-based MOF PCN-224(Fe) and followed by pyrolysis to obtain the single-atom Fe implanted N-doped porous carbons material PANI@PCN-224(Fe)-900. The introduced PANI inside the pores of PCN-224(Fe) not only served as protective fences to prevent the aggregation of the iron species during thermal annealing, but also acted as nitrogen sources to increase the nitrogen content and form Fe-Nx-C active sites. Compared with the pristine PCN-224(Fe) derived carbonization sample containing Fe-based particles, the carbonaceous material PANI@PCN-224(Fe)-900 without inactive Fe-based particles exhibited superb ORR electrocatalytic activity with a more positive half-wave potential, significantly improved stability in both alkaline media, and more challenging acidic condition. The migration-prevention strategy provides a new way to fabricate atomically dispersed metal active sites via pyrolysis approach for promoting catalysis.

scholarly journals A Cobalt-Iron Double-Atom Catalyst for the Oxygen Evolution Reaction

2019 ◽  
Author(s):  
Lichen Bai ◽  
Chia-Shuo Hsu ◽  
Duncan Alexander ◽  
Hao Ming Chen ◽  
Xile Hu
Keyword(s):  
Oxygen Evolution ◽  
Active Site ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Single Atom ◽  
X Ray ◽  
Highly Active ◽  
Cobalt Iron ◽  
X Ray Absorption

Single atom catalysts exhibit well-defined active sites and potentially maximum atomic efficiency. However, they are unsuitable for reactions that benefit from bimetallic promotion such as the oxygen evolution reaction (OER) in alkaline medium. Here we show that a single atom Co precatalyst can be in-situ transformed into a Co-Fe double atom catalyst for OER. This catalyst exhibits one of the highest turnover frequencies among metal oxides. Electrochemical, microscopic, and spectroscopic data including those from operando X-ray absorption spectroscopy, reveal a dimeric Co-Fe moiety as the active site of the catalyst. This work demonstrates double-atom catalysis as a promising approach for the developed of defined and highly active OER catalysts.

scholarly journals Insights into the role of an Fe–N active site in the oxygen reduction reaction on carbon-supported supramolecular catalysts

RSC Advances ◽  
2020 ◽  
Vol 10 (15) ◽  
pp. 8709-8716
Author(s):  
Lin Gu ◽  
Yunyun Dong ◽  
Yan Zhang ◽  
Bo Wang ◽  
Qing Yuan ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Site ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Supramolecular Catalysts

The PPYTZ–Fe/C catalyst containing Fe–N active sites exhibited high ORR catalytic activity and stability in alkaline media with a four-electron pathway progress.

scholarly journals Unveiling the high-activity origin of single-atom iron catalysts for oxygen reduction reaction

2018 ◽  
Vol 115 (26) ◽  
pp. 6626-6631 ◽  
Author(s):  
Liu Yang ◽  
Daojian Cheng ◽  
Haoxiang Xu ◽  
Xiaofei Zeng ◽  
Xin Wan ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Density Functional ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Alkaline Media ◽  
Single Atom ◽  
Iron Catalysts ◽  
Grand Challenge ◽  
Orr Activity

It is still a grand challenge to develop a highly efficient nonprecious-metal electrocatalyst to replace the Pt-based catalysts for oxygen reduction reaction (ORR). Here, we propose a surfactant-assisted method to synthesize single-atom iron catalysts (SA-Fe/NG). The half-wave potential of SA-Fe/NG is only 30 mV less than 20% Pt/C in acidic medium, while it is 30 mV superior to 20% Pt/C in alkaline medium. Moreover, SA-Fe/NG shows extremely high stability with only 12 mV and 15 mV negative shifts after 5,000 cycles in acidic and alkaline media, respectively. Impressively, the SA-Fe/NG-based acidic proton exchange membrane fuel cell (PEMFC) exhibits a high power density of 823 mW cm−2. Combining experimental results and density-functional theory (DFT) calculations, we further reveal that the origin of high-ORR activity of SA-Fe/NG is from the Fe-pyrrolic-N species, because such molecular incorporation is the key, leading to the active site increase in an order of magnitude which successfully clarifies the bottleneck puzzle of why a small amount of iron in the SA-Fe catalysts can exhibit extremely superior ORR activity.

Spectroscopic discernibility of dopants and axial ligands in pyridinic FeN4 environments relevant to single-atom catalysts for the oxygen reduction reaction

2020 ◽  
Author(s):  
Charlotte Gallenkamp ◽  
Ulrike Ingrid Kramm ◽  
Vera Krewald
Keyword(s):  
Oxygen Reduction Reaction ◽  
Small Molecules ◽  
Oxygen Reduction ◽  
Active Site ◽  
Reduction Reaction ◽  
Single Atom ◽  
Axial Ligands

Single-atom catalysts (SACs) activate small molecules, e.g. the oxygen reduction reaction is catalysed by FeNC materials. Because the nature of active site(s) in SACs is unclear, spectroscopic and computational insights...

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