skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Regulating the electronic structures of mixed B-site pyrochlore to enhance the turnover frequency in water oxidation
Abstract This paper describes the development of mixed B-site pyrochlore Y2MnRuO7electrocatalyst for oxygen evolution reaction (OER) in acidic media, a challenge for the development of low-temperature electrolyzer for green hydrogen production. Recently, several theories have been developed to understand the reaction mechanism for OER, though there is an  uncertainty in most of the cases, due to the complex surface structures. Several key factors such as lattice oxygen, defect, electronic structure, oxidation state, hydroxyl group and conductivity were identified and shown to be important to the OER activity. The contribution of each factor to the performance however is often not well understood, limiting their impact in guiding the design of OER electrocatalysts. In this work, we showed mixed B-site pyrochlore Y2MnRuO7catalyst exhibits 14 times higher turnover frequency (TOF) than RuO2while maintaining a low overpotential of ~ 300 mV for the entire testing period of 24 h in acidic electrolyte. X-ray photoelectron spectroscopy (XPS) analysis reveals that this B-site mixed pyrochlore Y2MnRuO7has a higher oxidation state of Ru than those of Y2Ru2O7, which could be crucial for improving OER performance as the broadened and lowered Ru 4d band resulted from the B-site substitution by Mn is beneficial to the OER kinetics.  more » « less
Award ID(s):
2055734
PAR ID:
10436692
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Springer Science + Business Media
Date Published:
Journal Name:
Nano Convergence
Volume:
9
Issue:
1
ISSN:
2196-5404
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, ChemCatChem)
    Abstract Based on the coincident onsets of oxygen evolution reaction (OER) and metal dissolution for many metal‐oxide catalysts it was suggested that OER triggers dissolution. It is believed that both processes share common intermediates, yet exact mechanistic details remain largely unknown. For example, there is still no clear understanding as to why rutile IrO2exhibits such an exquisite stability among water‐splitting electrocatalysts. Here, we employ density functional theory calculations to analyze interactions between water and the (110) surface of rutile RuO2and IrO2as a response to oxygen evolution involving lattice oxygen species. We observe that these oxides display qualitatively different interfacial behavior that should have important implications for their electrochemical stability. Specifically, it is found that IrO2(110) becomes further stabilized under OER conditions due to the tendency to form highly stable low oxidation state Ir(III) species. In contrast, Ru species at RuO2(110) are prone to facile reoxidation by solution water. This should facilitate the formation of high Ru oxidation state intermediates (>IV) accelerating surface restructuring and metal dissolution. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Small)
    Abstract Development of high‐performance, low‐cost catalysts for electrochemical water splitting is key to sustainable hydrogen production. Herein, ultrafast synthesis of carbon‐supported ruthenium–copper (RuCu/C) nanocomposites is reported by magnetic induction heating, where the rapid Joule's heating of RuCl3and CuCl2at 200 A for 10 s produces Ru–Cl residues‐decorated Ru nanocrystals dispersed on a CuClxscaffold, featuring effective Ru to Cu charge transfer. Among the series, the RuCu/C‐3 sample exhibits the best activity in 1 mKOH toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with an overpotential of only −23 and +270 mV to reach 10 mA cm−2, respectively. When RuCu/C‐3 is used as bifunctional catalysts for electrochemical water splitting, a low cell voltage of 1.53 V is needed to produce 10 mA cm−2, markedly better than that with a mixture of commercial Pt/C+RuO2(1.59 V). In situ X‐ray absorption spectroscopy measurements show that the bifunctional activity is due to reduction of the Ru–Cl residues at low electrode potentials that enriches metallic Ru and oxidation at high electrode potentials that facilitates the formation of amorphous RuOx. These findings highlight the unique potential of MIH in the ultrafast synthesis of high‐performance catalysts for electrochemical water splitting. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Nature Communications)
    Abstract Developing efficient catalysts is of paramount importance to oxygen evolution, a sluggish anodic reaction that provides essential electrons and protons for various electrochemical processes, such as hydrogen generation. Here, we report that the oxygen evolution reaction (OER) can be efficiently catalyzed by cobalt tetrahedra, which are stabilized over the surface of a Swedenborgite-type YBCo 4 O 7 material. We reveal that the surface of YBaCo 4 O 7 possesses strong resilience towards structural amorphization during OER, which originates from its distinctive structural evolution toward electrochemical oxidation. The bulk of YBaCo 4 O 7 composes of corner-sharing only CoO 4 tetrahedra, which can flexibly alter their positions to accommodate the insertion of interstitial oxygen ions and mediate the stress during the electrochemical oxidation. The density functional theory calculations demonstrate that the OER is efficiently catalyzed by a binuclear active site of dual corner-shared cobalt tetrahedra, which have a coordination number switching between 3 and 4 during the reaction. We expect that the reported active structural motif of dual corner-shared cobalt tetrahedra in this study could enable further development of compounds for catalyzing the OER. 
    more » « less
  4. ; ; ; ; ; ; ; ; (, Chemistry – A European Journal)
    Abstract In this work, an organic‐inorganic hybrid crystal, violet‐crystal (VC), was used to etch the nickel foam (NF) to fabricate a self‐standing electrode for the water oxidation reaction. The efficacy of VC‐assisted etching manifests the promising electrochemical performance towards the oxygen evolution reaction (OER), requiring only ~356 and ~376 mV overpotentials to reach 50 and 100 mA cm−2, respectively. The OER activity improvement is attributed to the collectively exhaustive effects arising from the incorporation of various elements in the NF, and the enhancement of active site density. Furthermore, the self‐standing electrode is robust, exhibiting a stable OER activity after 4,000 cyclic voltammetry cycles, and ~50 h. The anodic transfer coefficients (αa) show that the first electron transfer step is the rate‐determining step on the surface of NF‐VCs‐1.0 (NF etched by 1 g of VCs) electrode, while the chemical step involving dissociation following the first electron transfer step is identified as the rate‐limiting step in other electrodes. The lowest Tafel slope value observed in the NF‐VCs‐1.0 electrode indicates the high surface coverage of oxygen intermediates and more favorable OER reaction kinetics, as confirmed by high interfacial chemical capacitance and low charge transport/interfacial resistance. This work demonstrates the importance of VCs‐assisted etching of NF to activate the OER, and the ability to predict reaction kinetics and rate‐limiting step based onαavalues, which will open new avenues to identify advanced electrocatalysts for the water oxidation reaction. 
    more » « less
  5. ; ; ; ; ; (, Nanoscale)
    The current study reports AxA’1-xByB’1-yO3-𝛿 perovskite redox catalysts (RCs) for CO2-splitting and methane partial oxidation (POx) in a cyclic redox scheme. Strontium (Sr) and iron (Fe) were chosen as A and B site elements with A’ being lanthanum (La), samarium (Sm) or yttrium (Y), and B’ being manganese (Mn), or titanium (Ti) to tailor their equilibrium oxygen partial pressures (P_(O_2 ) s) for CO2-splitting and methane partial oxidation. DFT calculations were performed for predictive optimization of the oxide materials whereas experimental investigation confirmed the DFT predicted redox performance. The redox kinetics of the RCs improved significantly by 1 wt.% ruthenium (Ru) impregnation without affecting their redox thermodynamics. Ru impregnated LaFe0.375Mn0.625O3 (A=0, A’=La, B=Fe, and B’=Mn) was the most promising RC in terms of its superior redox performance (CH4/CO2 conversion >90% and CO selectivity~ 95%) at 800oC. Long-term redox testing over Ru impregnated LaFe0.375Mn0.625O3 indicated stable performance during the first 30 cycles following with a ~25% decrease in the activity during the last 70 cycles. Air treatment was effective to reactivate the redox catalyst. Detailed characterizations revealed the underlying mechanism for redox catalyst deactivation and reactivation. This study not only validated a DFT guided mixed oxide design strategy for CO2 utilization but also provides potentially effective approaches to enhance redox kinetics as well as long-term redox catalyst performance. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email