scholarly journals Surface reconstruction establishing Mott-Schottky heterojunction and built-in space-charging effect accelerating oxygen evolution reaction

Nano Research ◽  
2021 ◽  
Author(s):  
Yao Kang ◽  
Shuo Wang ◽  
Kwan San Hui ◽  
Shuxing Wu ◽  
Duc Anh Dinh ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Oxygen Evolution ◽  
Surface Reconstruction ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Density Functional ◽  
Electrochemical Process ◽  
Ex Situ ◽  
Catalytic Activities ◽  
Spectroscopy Studies

AbstractStructural reconstruction of nanomaterials offers a fantastic way to regulate the electronic structure of active sites and promote their catalytic activities. However, how to properly facilitate surface reconstruction to overcome large overpotential that stimulate the surface reconstruction has remained elusive. Herein, we adopt a facile approach to activate surface reconstruction on Ni(OH)2 by incorporating F anions to achieve electro-derived structural oxidation process and further boost its oxygen evolution reaction (OER) activity. Ex situ Raman and X-ray photoemission spectroscopy studies indicate that F ions incorporation facilitated surface reconstruction and promotes the original Ni(OH)2 transformed into a mesoporous and amorphous F-NiOOH layer during the electrochemical process. Density functional theory (DFT) calculation reveals that this self-reconstructed NiOOH induces a space-charge effect on the p-n junction interface, which not only promotes the absorption of intermediates species (*OH, *O, and *OOH) and charge-transfer process during catalysis, but also leads to a strong interaction of the p-n junction interface to stabilize the materials. This work opens up a new possibility to regulate the electronic structure of active sites and promote their catalytic activities.

scholarly journals Quantum chemistry of the oxygen evolution reaction on cobalt(ii,iii) oxide – implications for designing the optimal catalyst

2016 ◽  
Vol 188 ◽  
pp. 199-226 ◽  
Author(s):  
Craig P. Plaisance ◽  
Karsten Reuter ◽  
Rutger A. van Santen
Keyword(s):  
Electronic Structure ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Density Functional ◽  
Oxidation Potential ◽  
Water Addition ◽  
Wide Range ◽  
A Site ◽  
Intrinsic Reactivity

Density functional theory is used to examine the changes in electronic structure that occur during the oxygen evolution reaction (OER) catalyzed by active sites on three different surface terminations of Co3O4. These three active sites have reactive oxo species with differing degrees of coordination by Co cations – a μ3-oxo on the (311) surface, a μ2-oxo on the (110)-A surface, and an η-oxo on the (110)-B surface. The kinetically relevant step on all surfaces over a wide range of applied potentials is the nucleophilic addition of water to the oxo, which is responsible for formation of the O–O bond. The intrinsic reactivity of a site for this step is found to increase as the coordination of the oxo decreases with the μ3-oxo on the (311) surface being the least reactive and the η-oxo on the (110)-B surface being the most reactive. A detailed analysis of the electronic changes occurring during water addition on the three sites reveals that this trend is due to both a decrease in the attractive local Madelung potential on the oxo and a decrease in electron withdrawal from the oxo by Co neighbors. Applying a similar electronic structure analysis to the oxidation steps preceding water addition in the catalytic cycle shows that analogous electronic changes occur during this process, explaining a correlation observed between the oxidation potential of a site and its intrinsic reactivity for water addition. This concept is then used to specify criteria for the design of an optimal OER catalyst at a given applied potential.

Operando Unraveling Photothermal-Promoted Dynamic Active Sites Generation in Spinel NiFe2O4 for Oxygen Evolution

2020 ◽  
Author(s):  
Likun Gao ◽  
Xun Cui ◽  
Zewei Wang ◽  
Christopher Sewell ◽  
Zili Li ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Surface Reconstruction ◽  
Water Oxidation ◽  
Active Sites ◽  
Density Functional ◽  
Diblock Copolymers ◽  
High Current Density ◽  
Active Surface ◽  
Photothermal Effect ◽  
Highly Active

Abstract The ability to develop highly active and low-cost electrocatalysts represents an important endeavor toward accelerating sluggish water-oxidation kinetics. Herein, we report, for the first time, the implementation and unravelling of photothermal effect of spinel nanoparticles (NPs) on promoting dynamic active sites generation to markedly enhance their oxygen evolution reaction (OER) activity via an integrated operando Raman and density functional theory (DFT) study. Specifically, NiFe2O4 (NFO) NPs are first synthesized by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors. Upon the NIR light irradiation, the photothermal heating of the NFO-based electrode progressively raises the temperature, accompanied by a marked decrease of overpotential. Accordingly, only an overpotential of 309 mV is required to yield a high current density of 100 mA cm-2, greatly lower than recently-reported earth-abundant electrocatalysts. More importantly, photothermal effect of NFO NPs not only significantly reduces the activation energy necessitated for water splitting, but also facilitates surface reconstruction into high-active oxyhydroxides at lower potential (1.36 V) under OER conditions, as revealed by operando Raman spectra-electrochemistry. Moreover, the DFT calculation corroborates that these reconstructed (Ni,Fe)oxyhydroxides are electrocatalytically active sites as the kinetics barrier is largely reduced over pure NFO without surface reconstruction. Given the diversity of materials (metal oxides, sulfides, phosphides, etc.) possessing the photo-to-thermal conversion, this effect may thus provide a unique and robust platform to boost highly-active surface species in nanomaterials for fundamental understanding of enhanced performance that may underpin future advances in electrocatalysis, photocatalysis, solar energy conversion and renewable energy production.  

Electronic structure modulation of metal-free graphdiyne for acidic oxygen evolution reaction

2D Materials ◽  
2021 ◽  
Author(s):  
Zhiqiang Zheng ◽  
Yurui Xue ◽  
Yaqi Gao ◽  
Zhongqiang Wang ◽  
Shuya Zhao ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
High Performance ◽  
Carbon Materials ◽  
Metal Free ◽  
Catalytic Activities ◽  
Structure Modulation ◽  
Flexible Metal ◽  
Kinetics Of

Abstract Developing high-performance metal-free electrocatalysts for acidic oxygen evolution reaction (AOER) is highly desirable but remains great challenge. Here we report a rationally substituting sp-C strategy for the synthesis of methyl- and hydrogen-substituted graphdiyne (MGDY, HGDY) nanowires arrays as 3D porous flexible metal-free electrodes for AOER. Methyl group in MGDY with stronger electron-pushing effect makes electrons around the acetylenic carbon atoms more delocalized, resulting in more uneven distributed surface charge, and higher intrinsic catalytic activities for AOER than HGDY, with the smaller overpotential of 406 mV at 10 mA cm−2 than HGDY and previously reported metal-free electrocatalysts. Our results reveal that the modulation of the electronic structure of GDY by selectively substituting sp-C allows for facilitating charge transfer kinetics, improving adsorption of reaction intermediate, and thereby accelerating the sluggish kinetics of AOER. This work provides us an ideal opportunity for studying the exact HER/OER mechanisms of metal-free carbon materials.

Improving the oxygen evolution reaction using electronic structure modulation of sulfur-retaining nickel-based electrocatalysts

2021 ◽  
Author(s):  
Man Ho Han ◽  
Min-wook Pin ◽  
Jai Hyun Koh ◽  
Jong Hyeok Park ◽  
Jihyun Kim ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Transition Metals ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Experimental Studies ◽  
Promising Method ◽  
Catalytic Activities ◽  
Structure Modulation

The sulfurization of transition metals is a promising method for improving their catalytic activities in the oxygen evolution reaction (OER). However, experimental studies regarding the effects of undissolved, remaining S...

Polyaniline Coating Enables Electronic Structure Engineering in Fe3O4 to Promote Alkaline Oxygen Evolution Reaction

2021 ◽  
Author(s):  
Yang Zou ◽  
Yuan Huang ◽  
Liwen Jiang ◽  
Arindam Indra ◽  
Yongqing Wang ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Simple Process ◽  
Molecular Modification ◽  
Mild Conditions ◽  
Novel Strategy ◽  
Structure Engineering

Abstract The electronic structure of active sites is of importance for catalysts to achieve an optimized interaction with the intermediates. In this study, a unique organic-inorganic hybrid oxygen evolution reaction (OER) electrocatalyst composed of electrochemically inactive conducting polyaniline (PANI) and non-precious Fe-based oxide Fe3O4 is presented. PANI molecules were in-situ loaded on Fe3O4 nanoparticles through an efficient and simple process under mild conditions. The electronic structure of Fe3O4 was modulated by creating a strong interaction with PANI molecules, leading to enhanced activity and stability of the catalyst to achieve 10 mA cm-2 geometrical current density at overpotential of 265 mV in 1 M aqueous KOH solution. This work demonstrates that a highly efficient electrocatalyst can be achieved by molecular modification and provides a novel strategy for the optimization of the inactive non-precious catalysts.

scholarly journals Perovskite With Tunable Active-Sites Oxidation State by High-Valence W for Enhanced Oxygen Evolution Reaction

2022 ◽  
Vol 9 ◽  
Author(s):  
Jiabiao Yan ◽  
Mingkun Xia ◽  
Chenguang Zhu ◽  
Dawei Chen ◽  
Fanglin Du
Keyword(s):  
Electronic Structure ◽  
Water Splitting ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Precious Metal ◽  
Active Sites ◽  
Perovskite Oxides ◽  
Intrinsic Activity ◽  
Excellent Activity ◽  
The Stability

Perovskite oxides have been established as a promising kind of catalyst for alkaline oxygen evolution reactions (OER), because of their regulated non-precious metal components. However, the surface lattice is amorphous during the reaction, which gradually decreases the intrinsic activity and stability of catalysts. Herein, the precisely control tungsten atoms substituted perovskite oxides (Pr0.5Ba0.5Co1-xWxO3-δ) nanowires were developed by electrostatic spinning. The activity and Tafel slope were both dependent on the W content in a volcano-like fashion, and the optimized Pr0.5Ba0.5Co0.8W0.2O3-δ exhibits both excellent activity and superior stability compared with other reported perovskite oxides. Due to the outermost vacant orbitals of W6+, the electronic structure of cobalt sites could be efficiently optimized. Meanwhile, the stronger W-O bond could also significantly improve the stability of latticed oxide atoms to impede the generation of surface amorphous layers, which shows good application value in alkaline water splitting.

scholarly journals Operando unraveling photothermal-promoted dynamic active-sites generation in NiFe2O4 for markedly enhanced oxygen evolution

2021 ◽  
Vol 118 (7) ◽  
pp. e2023421118
Author(s):  
Likun Gao ◽  
Xun Cui ◽  
Zewei Wang ◽  
Christopher D. Sewell ◽  
Zili Li ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Surface Reconstruction ◽  
Water Oxidation ◽  
Active Sites ◽  
Density Functional ◽  
Diblock Copolymers ◽  
High Current Density ◽  
Infrared Light ◽  
Photothermal Effect ◽  
Highly Active

The ability to develop highly active and low-cost electrocatalysts represents an important endeavor toward accelerating sluggish water-oxidation kinetics. Herein, we report the implementation and unraveling of the photothermal effect of spinel nanoparticles (NPs) on promoting dynamic active-sites generation to markedly enhance their oxygen evolution reaction (OER) activity via an integrated operando Raman and density functional theory (DFT) study. Specifically, NiFe2O4 (NFO) NPs are first synthesized by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors. Upon the near-infrared light irradiation, the photothermal heating of the NFO-based electrode progressively raises the temperature, accompanied by a marked decrease of overpotential. Accordingly, only an overpotential of 309 mV is required to yield a high current density of 100 mA cm−2, greatly lower than recently reported earth-abundant electrocatalysts. More importantly, the photothermal effect of NFO NPs facilitates surface reconstruction into high-active oxyhydroxides at lower potential (1.36 V) under OER conditions, as revealed by operando Raman spectroelectrochemistry. The DFT calculation corroborates that these reconstructed (Ni,Fe)oxyhydroxides are electrocatalytically active sites as the kinetics barrier is largely reduced over pure NFO without surface reconstruction. Given the diversity of materials (metal oxides, sulfides, phosphides, etc.) possessing the photo-to-thermal conversion, this effect may thus provide a unique and robust platform to boost highly active surface species in nanomaterials for a fundamental understanding of enhanced performance that may underpin future advances in electrocatalysis, photocatalysis, solar-energy conversion, and renewable-energy production.

Tuning oxide activity through modification of the crystal and electronic structure: from strain to potential polymorphs

2015 ◽  
Vol 17 (43) ◽  
pp. 28943-28949 ◽  
Author(s):  
Zhongnan Xu ◽  
John R. Kitchin
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Density Functional ◽  
Oxide Catalysts ◽  
Structure Sensitivity ◽  
Functional Theory ◽  
Crystal And Electronic Structure

The structure-sensitivity of oxide catalysts is explored using density functional theory. The potential activities of undiscovered, oxide polymorphs are evaluated for use in the oxygen evolution reaction.

Towards a Design of Active Oxygen Evolution Catalysts: Insights from Automated Density Functional Theory Calculations and Machine Learning

2019 ◽  
Author(s):  
Seoin Back ◽  
Kevin Tran ◽  
Zachary Ulissi
Keyword(s):  
Machine Learning ◽  
Oxygen Evolution ◽  
Active Sites ◽  
Density Functional ◽  
Chemical Space ◽  
Density Functional Theory Calculations ◽  
Catalyst Design ◽  
Transition Metal Catalysts ◽  
Oxide Materials ◽  
Design Strategies

<div> <div> <div> <div><p>Developing active and stable oxygen evolution catalysts is a key to enabling various future energy technologies and the state-of-the-art catalyst is Ir-containing oxide materials. Understanding oxygen chemistry on oxide materials is significantly more complicated than studying transition metal catalysts for two reasons: the most stable surface coverage under reaction conditions is extremely important but difficult to understand without many detailed calculations, and there are many possible active sites and configurations on O* or OH* covered surfaces. We have developed an automated and high-throughput approach to solve this problem and predict OER overpotentials for arbitrary oxide surfaces. We demonstrate this for a number of previously-unstudied IrO2 and IrO3 polymorphs and their facets. We discovered that low index surfaces of IrO2 other than rutile (110) are more active than the most stable rutile (110), and we identified promising active sites of IrO2 and IrO3 that outperform rutile (110) by 0.2 V in theoretical overpotential. Based on findings from DFT calculations, we pro- vide catalyst design strategies to improve catalytic activity of Ir based catalysts and demonstrate a machine learning model capable of predicting surface coverages and site activity. This work highlights the importance of investigating unexplored chemical space to design promising catalysts.<br></p></div></div></div></div><div><div><div> </div> </div> </div>

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