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 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.

Revealing the structural transformation of rutile RuO2via in situ X-ray absorption spectroscopy during the oxygen evolution reaction

2019 ◽  
Vol 48 (21) ◽  
pp. 7122-7129 ◽  
Author(s):  
Chia-Jui Chang ◽  
You-Chiuan Chu ◽  
Hao-Yu Yan ◽  
Yen-Fa Liao ◽  
Hao Ming Chen
Keyword(s):  
Oxygen Evolution ◽  
Structural Transformation ◽  
Absorption Spectroscopy ◽  
Oxygen Evolution Reaction ◽  
The State ◽  
X Ray ◽  
Alkaline Conditions ◽  
X Ray Absorption ◽  
State Of Art

The state-of-art RuO2 catalyst for the oxygen evolution reaction (OER) is measured by using in situ X-ray absorption spectroscopy (XAS) to elucidate the structural transformation during catalyzing the reaction in acidic and alkaline conditions.

scholarly journals Nitrogen-Doped Sponge Ni Fibers as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Kaili Zhang ◽  
Xinhui Xia ◽  
Shengjue Deng ◽  
Yu Zhong ◽  
Dong Xie ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Photoelectron Spectroscopy ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
High Performance ◽  
Active Phase ◽  
X Ray ◽  
Highly Active ◽  
N Doping ◽  
Energy Conversion Devices

Abstract Controllable synthesis of highly active micro/nanostructured metal electrocatalysts for oxygen evolution reaction (OER) is a particularly significant and challenging target. Herein, we report a 3D porous sponge-like Ni material, prepared by a facile hydrothermal method and consisting of cross-linked micro/nanofibers, as an integrated binder-free OER electrocatalyst. To further enhance the electrocatalytic performance, an N-doping strategy is applied to obtain N-doped sponge Ni (N-SN) for the first time, via NH3 annealing. Due to the combination of the unique conductive sponge structure and N doping, the as-obtained N-SN material shows improved conductivity and a higher number of active sites, resulting in enhanced OER performance and excellent stability. Remarkably, N-SN exhibits a low overpotential of 365 mV at 100 mA cm−2 and an extremely small Tafel slope of 33 mV dec−1, as well as superior long-term stability, outperforming unmodified sponge Ni. Importantly, the combination of X-ray photoelectron spectroscopy and near-edge X-ray adsorption fine structure analyses shows that γ-NiOOH is the surface-active phase for OER. Therefore, the combination of conductive sponge structure and N-doping modification opens a new avenue for fabricating new types of high-performance electrodes with application in electrochemical energy conversion devices.

scholarly journals Double-Atom Catalysts Provide a Molecular Platform for Oxygen Evolution

2019 ◽  
Author(s):  
Lichen Bai ◽  
Chia-Shuo Hsu ◽  
Duncan Alexander ◽  
Hao Ming Chen ◽  
Xile Hu
Keyword(s):  
Oxygen Evolution ◽  
Active Sites ◽  
Supported Catalysts ◽  
Single Atom ◽  
Bond Forming ◽  
Co2 Electroreduction ◽  
Anode Reaction ◽  
X Ray Absorption ◽  
General Synthesis

The oxygen evolution reaction (OER) is an essential anode reaction for the generation of solar and electric fuels through water splitting or CO2 electroreduction. Mixed metal oxides containing Co, Fe, or Ni prove to be the most promising OER electrocatalysts in alkaline medium. However, the active sites and reaction mechanisms of these catalysts are difficult to study due to their heterogeneous nature. Here we describe a general synthesis of Co, Fe, and Ni-containing double-atom catalysts from their single-atom precursors via in-situ electrochemical transformation. Atomic-resolution microscopy and operando X-ray absorption spectroscopy (XAS) reveal molecule-like bimetallic active sites for these supported catalysts. Based on electrokinetic and XAS data, we propose a complete catalytic cycle for each catalyst. These mechanisms follow a similar O-O bond forming step and all exhibit bimetallic cooperation. However, the mechanisms diverge in the site and source of OH- for O-O bond formation as well as the order of proton and electron transfer. Our work demonstrates double-atom catalysts as an attractive platform for fundamental studies of heterogeneous OER electrocatalysts.

Unveiling the active sites of Ni–Fe phosphide/metaphosphate for efficient oxygen evolution under alkaline conditions

2019 ◽  
Vol 55 (53) ◽  
pp. 7687-7690 ◽  
Author(s):  
Can Huang ◽  
Ying Zou ◽  
Ya-Qian Ye ◽  
Ting Ouyang ◽  
Kang Xiao ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Highly Active ◽  
Alkaline Conditions ◽  
Stable Oxygen

The highly active and stable oxygen evolution reaction (OER) performance of Ni–Fe phosphide/metaphosphate (Ni1−xFex-P/PO3) can originate from in situ generated Fe doped γ-NiOOH.

scholarly journals Double-Atom Catalysts Provide a Molecular Platform for Oxygen Evolution

2019 ◽  
Author(s):  
Lichen Bai ◽  
Chia-Shuo Hsu ◽  
Duncan Alexander ◽  
Hao Ming Chen ◽  
Xile Hu
Keyword(s):  
Oxygen Evolution ◽  
Active Sites ◽  
Supported Catalysts ◽  
Single Atom ◽  
Bond Forming ◽  
Co2 Electroreduction ◽  
Anode Reaction ◽  
X Ray Absorption ◽  
General Synthesis

The oxygen evolution reaction (OER) is an essential anode reaction for the generation of solar and electric fuels through water splitting or CO2 electroreduction. Mixed metal oxides containing Co, Fe, or Ni prove to be the most promising OER electrocatalysts in alkaline medium. However, the active sites and reaction mechanisms of these catalysts are difficult to study due to their heterogeneous nature. Here we describe a general synthesis of Co, Fe, and Ni-containing double-atom catalysts from their single-atom precursors via in-situ electrochemical transformation. Atomic-resolution microscopy and operando X-ray absorption spectroscopy (XAS) reveal molecule-like bimetallic active sites for these supported catalysts. Based on electrokinetic and XAS data, we propose a complete catalytic cycle for each catalyst. These mechanisms follow a similar O-O bond forming step and all exhibit bimetallic cooperation. However, the mechanisms diverge in the site and source of OH- for O-O bond formation as well as the order of proton and electron transfer. Our work demonstrates double-atom catalysts as an attractive platform for fundamental studies of heterogeneous OER electrocatalysts.

scholarly journals The Evolution Pathway from Iron Compounds to Fe1(II)-N4 Sites Through Gas-Phase Iron During Pyrolysis

2019 ◽  
Author(s):  
Jingkun Li ◽  
Li Jiao ◽  
Evan Wegener ◽  
Lynne K. LaRochelle Richard ◽  
Ershuai Liu ◽  
...  
Keyword(s):  
Gas Phase ◽  
Active Sites ◽  
Active Catalyst ◽  
Reduction Reaction ◽  
Physical Contact ◽  
Single Atom ◽  
Iron Compounds ◽  
X Ray ◽  
Highly Active ◽  
X Ray Absorption

<div> <div> <div> <p>Pyrolysis is indispensable for synthesizing highly active Fe-N-C catalysts for the oxygen reduction reaction (ORR) in acid, but how Fe, N, and C precursors transform to ORR-active sites during pyrolysis remains unclear. This knowledge gap ob- scures the connections between the input precursors and output products, clouding the pathway toward Fe-N-C catalyst improve- ment. Herein, we unravel the evolution pathway of precursors to ORR-active catalyst comprised exclusively of single atom Fe1(II)- N4 sites via in-temperature X-ray absorption spectroscopy. The Fe precursor transforms to Fe oxides below 300 °C, and then to tetrahedral Fe1(II)-O4 via a crystal-to-melt-like transformation below 600 °C. The Fe1(II)-O4 releases a single Fe atom that flows into the N-doped carbon defect forming Fe1(II)-N4 above 600 °C. This vapor phase single Fe atom transport mechanism is verified by synthesizing Fe1(II)-N4 sites via “non-contact pyrolysis” wherein the Fe precursor is not in physical contact with the N and C precursors during pyrolysis. </p> </div> </div> </div>

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