scholarly journals Operando spectroscopic observation of dynamic-coupling oxygen on single-atomic iridium catalyst for acidic water oxidation

2021 ◽  
Author(s):  
Hui Su ◽  
Wanlin Zhou ◽  
Wu Zhou ◽  
Yuanli Li ◽  
Li Rong Zheng ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Large Mass ◽  
Spectroscopic Observation ◽  
Proton Exchange ◽  
Dynamic Coupling ◽  
Exchange Membrane ◽  
X Ray Absorption ◽  
Increased Activity

Abstract Uncovering the dynamics of active sites under working state is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at atomic level a potential-driven dynamic-coupling oxygen on the hetero-nitrogen configured single-atomic Ir sites (HN-Ir NC) during OER working conditions to successfully endow the single-atomic Ir catalyst with an ultrahigh electrochemical acidic-OER activity. Using operando synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe in the experiment that a dynamic oxygen atom is formed at the Ir site with the O-hetero-Ir-N4 structure as more electrophilic active center and then effectively promote the generation of the key *OOH intermediates under working potentials, which is exceptionally favourable for the dissociation of H2O over Ir sites and resistance to over-oxidation and dissolution of the active sites.The optimal single-atomic HN-Ir NC catalyst delivers a large mass activity of 2860 A gmetal−1 and a huge turnover frequency of 5110 h− 1 at a low overpotential of 216 mV (10 mA cm− 2), 480˗510 times than that of commercial IrO2 catalyst. More importantly, the HN-Ir NC catalyst shows no evident deactivation after continuous 100 h OER operation in acidic medium.

scholarly journals In-situ spectroscopic observation of dynamic-coupling oxygen on atomically dispersed iridium electrocatalyst for acidic water oxidation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hui Su ◽  
Wanlin Zhou ◽  
Wu Zhou ◽  
Yuanli Li ◽  
Lirong Zheng ◽  
...  
Keyword(s):  
Working Conditions ◽  
Water Oxidation ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Large Mass ◽  
Spectroscopic Observation ◽  
Proton Exchange ◽  
Dynamic Coupling ◽  
Active Centre

AbstractUncovering the dynamics of active sites in the working conditions is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at the atomic level potential-driven dynamic-coupling oxygen on atomically dispersed hetero-nitrogen-configured Ir sites (AD-HN-Ir) in the OER working conditions to successfully provide the atomically dispersed Ir electrocatalyst with ultrahigh electrochemical acidic OER activity. Using in-situ synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe that one oxygen atom is formed at the Ir active site with an O-hetero-Ir-N4 structure as a more electrophilic active centre in the experiment, which effectively promotes the generation of key *OOH intermediates under working potentials; this process is favourable for the dissociation of H2O over Ir active sites and resistance to over-oxidation and dissolution of the active sites. The optimal AD-HN-Ir electrocatalyst delivers a large mass activity of 2860 A gmetal−1 and a large turnover frequency of 5110 h−1 at a low overpotential of 216 mV (10 mA cm−2), 480–510 times larger than those of the commercial IrO2. More importantly, the AD-HN-Ir electrocatalyst shows no evident deactivation after continuous 100 h OER operation in an acidic medium.

scholarly journals Degradation and regeneration of Fe-Nx active sites for oxygen reduction reaction: the role of surface oxidation, Fe demetallation and local carbon microporosity

2021 ◽  
Author(s):  
Dongsheng Xia ◽  
Chenchen Yu ◽  
Yinghao Zhao ◽  
Yinping Wei ◽  
Haiyan Wu ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Degradation Mechanism ◽  
Surface Oxidation ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Exchange Membrane

The severe degradation of Fe-N-C electrocatalysts during long-term oxygen reduction reaction (ORR) has become a major obstacle for application in proton-exchange membrane fuel cells. Understanding the degradation mechanism and regeneration...

scholarly journals Intermetallic Platinum Alloy Nanoparticles and Single Atoms Hybrid Electrocatalysts for Proton Exchange Membrane Fuel Cells

2021 ◽  
Author(s):  
Minhua Shao ◽  
Fei Xiao ◽  
Qi Wang ◽  
Gui-Liang Xu ◽  
Xueping Qin ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Synergistic Effects ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Alloy Nanoparticles ◽  
Single Atoms ◽  
Low Pt Loading ◽  
Exchange Membrane

Abstract Proton exchange membrane fuel cell converts hydrogen and oxygen into electricity with zero emission1. The high cost and low durability of Pt-based electrocatalysts for oxygen reduction reaction hinder its wide applications2,3. The development of non-precious metal electrocatalysts also reaches the bottleneck because of the low activity and durability4,5. Here we rationally design a hybrid electrocatalyst consisting of atomically dispersed Pt and Fe single atoms and intermetallic PtFe alloy nanoparticles. The Pt mass activity of the hybrid catalyst is 3.5 times higher than that of commercial Pt/C in a fuel cell. More importantly, the fuel cell with an ultra-low Pt loading in the cathode (0.015 mgPt cm-2) shows unprecedented durability, with 93.6% activity retention after 100,000 cycles and no noticeable current drop at 0.6 V for at least 206 h. These results highlight the importance of the synergistic effects among active sites in hybrid electrocatalysts and provide an alternative way to design more active and durable low-Pt electrocatalysts for electrochemical devices.

High-density active sites porous Fe/N/C electrocatalyst boosting the performance of proton exchange membrane fuel cells

2018 ◽  
Vol 401 ◽  
pp. 287-295 ◽  
Author(s):  
Rui Wu ◽  
Yujie Song ◽  
Xun Huang ◽  
Siguo Chen ◽  
Shumaila Ibraheem ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
High Density ◽  
Exchange Membrane

Electrospun Nafion Nanofiber for Proton Exchange Membrane Fuel Cell Application

2009 ◽  
Vol 6 (3) ◽  
Author(s):  
R. Bajon ◽  
S. Balaji ◽  
S. M. Guo
Keyword(s):  
Electric Field ◽  
Porous Structure ◽  
Active Sites ◽  
Proton Exchange Membrane ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Membrane Electrode ◽  
Surface Charges ◽  
Power Sources ◽  
Exchange Membrane

Proton exchange membrane fuel cells (PEMFCs) are attractive power plants for use in many applications, including portable power sources, electric vehicles, and on-site combined power/heat plants, due to the inherently high efficiency and low emission. The membrane electrode assembly (MEA) is the key component of a PEMFC. A standard five layer MEA consists of a proton exchange membrane, two catalyst layers, and two gas diffusion layers. The most commonly used electrolyte material is proton conductive perfluorinated sulfonic acid membrane, such as Nafion. Hydrogen is oxidized at the anode/electrolyte interface, the so-called triple-phase-boundary (TPB) active sites. TPB region must be a good electron conductor, a good ion conductor, and a porous structure for fuel/air diffusion. Typical PEMFC TPB is a porous structure made with Nafion and catalyst particle mixture. In this paper, electrospinning is used to synthesize polymer/Nafion nanofibers. Electrospinning is a straightforward method that has been successfully used to prepare fibers or fiber mats from a broad range of organic polymers. In the electrospinning process, a polymer solution held by its surface tension at the end of a capillary tube is subjected to an electric field, and as the electric field strength increases, a solid fiber is generated as the electrified jet is continuously stretched because of the electrostatic repulsions between the surface charges and the evaporation of solvent. Uniform one-dimensional Nafion nanofibers have been fabricated using Nafion solution and solutions containing polyvinyl pyrrolidone, polyethylene oxide, and polyvinyl alcohol. The morphologies of polymer/Nafion nanofibers, fabricated under different electrospinning conditions and different polymer compositions, are presented.

Fe–N–C electrocatalyst with dense active sites and efficient mass transport for high-performance proton exchange membrane fuel cells

2019 ◽  
Vol 2 (3) ◽  
pp. 259-268 ◽  
Author(s):  
Xin Wan ◽  
Xiaofang Liu ◽  
Yongcheng Li ◽  
Ronghai Yu ◽  
Lirong Zheng ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Mass Transport ◽  
Active Sites ◽  
High Performance ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Exchange Membrane

Defects tailoring IrO2@TiN1+x nano-heterojunction for superior water oxidation activity and stability

2021 ◽  
Author(s):  
Sen Wang ◽  
Hong Lv ◽  
Songhu Bi ◽  
Tianqi Li ◽  
Yongwen Sun ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Proton Exchange Membrane ◽  
Water Electrolysis ◽  
Cost Effective ◽  
Proton Exchange ◽  
Pragmatic Approach ◽  
Oxidation Activity ◽  
Anode Catalysts ◽  
Exchange Membrane

Developing cost-effective Ir-based anode catalysts for proton exchange membrane (PEM) water electrolysis has been recognized as an efficient and pragmatic approach, however, many challenges remain to lower Ir content while...

In Situ X-ray Absorption Spectroscopy to Monitor the Degradation of Fe/N/C Cathode Catalyst in Proton Exchange Membrane Fuel Cells

2021 ◽  
Vol 168 (1) ◽  
pp. 014513
Author(s):  
Y. Nabae ◽  
Q. Yuan ◽  
S. Nagata ◽  
K. Kusaba ◽  
T. Aoki ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Absorption Spectroscopy ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Cathode Catalyst ◽  
X Ray ◽  
Exchange Membrane ◽  
X Ray Absorption

scholarly journals A spectroscopic proton-exchange membrane fuel cell test setup allowing fluorescence x-ray absorption spectroscopy measurements during state-of-the-art cell tests

2011 ◽  
Vol 82 (4) ◽  
pp. 044101 ◽  
Author(s):  
Olga Petrova ◽  
Christian Kulp ◽  
Maurits W. E. van den Berg ◽  
Konstantin V. Klementiev ◽  
Bruno Otto ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Absorption Spectroscopy ◽  
Proton Exchange Membrane ◽  
State Of The Art ◽  
Proton Exchange ◽  
Test Setup ◽  
X Ray ◽  
Cell Test ◽  
Exchange Membrane ◽  
X Ray Absorption

scholarly journals Electrochemical characterization of manganese oxides as a water oxidation catalyst in proton exchange membrane electrolysers

2019 ◽  
Vol 6 (5) ◽  
pp. 190122 ◽  
Author(s):  
Toru Hayashi ◽  
Nadège Bonnet-Mercier ◽  
Akira Yamaguchi ◽  
Kazumasa Suetsugu ◽  
Ryuhei Nakamura
Keyword(s):  
Water Oxidation ◽  
Manganese Oxides ◽  
Proton Exchange Membrane ◽  
Water Electrolysis ◽  
Electrode System ◽  
Proton Exchange ◽  
Oxidation Catalyst ◽  
Carbon Supports ◽  
Exchange Membrane ◽  
Mn Oxides

The performance of four polymorphs of manganese (Mn) dioxides as the catalyst for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) electrolysers was examined. The comparison of the activity between Mn oxides/carbon (Mn/C), iridium oxide/carbon (Ir/C) and platinum/carbon (Pt/C) under the same condition in PEM electrolysers showed that the γ-MnO 2 /C exhibited a voltage efficiency for water electrolysis comparable to the case with Pt/C, while lower than the case with the benchmark Ir/C OER catalyst. The rapid decrease in the voltage efficiency was observed for a PEM electrolyser with the Mn/C, as indicated by the voltage shift from 1.7 to 1.9 V under the galvanostatic condition. The rapid deactivation was also observed when Pt/C was used, indicating that the instability of PEM electrolysis with Mn/C is probably due to the oxidative decomposition of carbon supports. The OER activity of the four types of Mn oxides was also evaluated at acidic pH in a three-electrode system. It was found that the OER activity trends of the Mn oxides evaluated in an acidic aqueous electrolyte were distinct from those in PEM electrolysers, demonstrating the importance of the evaluation of OER catalysts in a real device condition for future development of noble-metal-free PEM electrolysers.

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