scholarly journals Modulating Ni/Ce Ratio in NiyCe100−yOx Electrocatalysts for Enhanced Water Oxidation

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 437
Author(s):  
Jun Yu ◽  
Qi Cao ◽  
Chen Qiu ◽  
Lei Chen ◽  
Jean-Jacques Delaunay
Keyword(s):  
Oxygen Vacancy ◽  
Water Oxidation ◽  
Oxygen Vacancies ◽  
Direct Relationship ◽  
Small Mass ◽  
Transfer Resistance ◽  
Long Term Stability ◽  
Surface Areas ◽  
Tafel Slopes

Oxygen evolution reaction (OER) is the key reaction for water splitting, which is used for hydrogen production. Oxygen vacancy engineering is an effective method to tune the OER performance, but the direct relationship between the concentration of oxygen vacancy and OER activity is not well understood. Herein, a series of NiyCe100−yOx with different concentration of oxygen vacancies were successfully synthesized. The larger concentration of oxygen vacancies in Ni75Ce25Ox and Ni50Ce50Ox result in their lower Tafel slopes, small mass-transfer resistance, and larger electrochemical surface areas of the catalysts, which account for the higher OER activities for these two catalysts. Moreover, with a fixed current density of 10 mA/cm2, the potential remains stable at 1.57 V for more than 100 h, indicating the long-term stability of the Ni75Ce25Ox catalyst.

3D ordered porous SnO2 with a controllable pore diameter for enhanced formaldehyde sensing performance

2020 ◽  
Vol 13 (07) ◽  
pp. 2051044
Author(s):  
Dan Sun ◽  
Huixiao Guo ◽  
Yu Li ◽  
Haiying Li ◽  
Xiaosong Li ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Porous Structures ◽  
Gas Sensitivity ◽  
Long Term Stability ◽  
Response Recovery ◽  
Recovery Times ◽  
Formaldehyde Sensing ◽  
Different Diameters ◽  
Ordered Porous

This paper reports the preparation of 3D ordered porous SnO2 with different diameters (103, 546, and 1030[Formula: see text]nm) by a simple template method. We find that 103[Formula: see text]nm porous SnO2 nanomaterials have the highest response (30) and fastest response/recovery time (3/10 s) for 100 ppm HCHO (formaldehyde) compared with the response and response/recovery times for 546 nm (20 and 3/17[Formula: see text]s, respectively) and 1030 nm (10 and 6/20[Formula: see text]s, respectively) porous SnO2 nanomaterials at a low working temperature (220∘C). All three sensors show good long-term stability, repeatability, and linearity. The results show that decreasing the diameter of the porous SnO2 materials effectively increased the gas sensitivity to HCHO. The increase in the gas sensitivity was attributed to the ordered porous structures, large specific surface area, and additional oxygen vacancies on the surface.

A high-performance silicon photoanode enabled by oxygen vacancy modulation on NiOOH electrocatalyst for water oxidation

Nanoscale ◽  
2020 ◽  
Vol 12 (14) ◽  
pp. 7550-7556 ◽  
Author(s):  
Qian Cai ◽  
Wenting Hong ◽  
Chuanyong Jian ◽  
Wei Liu
Keyword(s):  
Oxygen Vacancy ◽  
Water Oxidation ◽  
High Performance ◽  
Oxygen Vacancies ◽  
Co Catalyst

NiFe nanoparticles which are deposited onto the n-Si/Ni/NiOOH photoanode surface lead to high OER performance by acting as a co-catalyst and creating oxygen vacancies.

Determining the Role of Oxygen Vacancies in the Photocatalytic Performance of WO3 for Water Oxidation

2019 ◽  
Author(s):  
Sacha Corby ◽  
Laia Francàs ◽  
Andreas Kafizas ◽  
James R Durrant
Keyword(s):  
Oxygen Vacancy ◽  
Charge Carrier ◽  
Water Oxidation ◽  
Oxygen Vacancies ◽  
Photocatalytic Performance ◽  
Photoelectrochemical Performance ◽  
Solar Water Splitting ◽  
The Impact ◽  
Recombination Kinetics ◽  
Vacancy Concentrations

Oxygen vacancies are common to most metal oxides, whether intentionally incorporated or otherwise, and the study of these defects is of increasing interest for solar water splitting. In this work, we examine nanostructured WO<sub>3</sub> photoanodes of varying oxygen content to determine how the concentration of bulk oxygen-vacancy states affects the photocatalytic performance for water oxidation. Using transient optical spectroscopy, we follow the charge carrier recombination kinetics in these samples, from picoseconds to seconds, and examine how differing oxygen vacancy concentrations impact upon these kinetics. We find that samples with an intermediate concentration of vacancies (~2% of oxygen atoms) afford the greatest photoinduced charge carrier densities, and the slowest recombination kinetics across all timescales studied. This increased yield of photogenerated charges correlates with improved photocurrent densities under simulated sunlight, with both greater and lesser oxygen vacancy concentrations resulting in enhanced recombination losses and poorer J-V performances. Our conclusion, that an optimal – neither too high nor too low – concentration of oxygen vacancies is required for optimum photoelectrochemical performance, is discussed in terms of the impact of these defects on charge separation and transport, as well as the implications held for other highly doped materials for photoelectrochemical water oxidation.

scholarly journals Highly Efficient and Stable Hydrogen Production in All pH Range by Two-Dimensional Structured Metal-Doped Tungsten Semicarbides

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Edison H. Ang ◽  
Khang N. Dinh ◽  
Xiaoli Sun ◽  
Ying Huang ◽  
Jun Yang ◽  
...  
Keyword(s):  
Density Functional ◽  
Functional Theory ◽  
Faradaic Efficiency ◽  
Long Term Stability ◽  
Optimal Value ◽  
Tafel Slopes ◽  
Electrochemical Water Splitting ◽  
Ph Range ◽  
Metal Doped

Transition-metal-doped tungsten semicarbide nanosheets (M-doped W2C NSs, M=Fe, Co, and Ni) have been synthesized through carburization of the mixture of tungsten trioxide, polyvinylpyrrolidone, and metal dopant. The nanosheets grow directly on the W mesh and have the lateral dimension of several hundreds of nm to a few μm with a thickness of few tens nm. It is demonstrated that the M-doped W2C NSs exhibit superior electrocatalytic activity for hydrogen evolution reaction (HER). Impressively, the Ni-doped W2C NSs (2 at% Ni) with the optimized HER activity show extremely low onset overpotentials of 4, 9, and 19 mV and modest Tafel slopes of 39, 51, and 87 mV dec−1 in acidic (pH=0), neutral (pH=7.2), and basic (pH=14) solutions, respectively, which is close to the commercial Pt/C catalyst. Density functional theory (DFT) calculations also demonstrate that the Gibbs free energy for H adsorption of Ni-W2C is much closer to the optimal value ∆GH⁎ = -0.073 eV as compared to -0.16 eV of W2C. Furthermore, nearly 100% Faradaic efficiency and long-term stability are obtained in those environments. This realization of highly tolerant metal semicarbide catalyst performing on par with commercial Pt/C in all range of pH offers a key step towards industrially electrochemical water splitting.

Ethylene glycol-mediated one-pot synthesis of Fe incorporated α-Ni(OH)2 nanosheets with enhanced intrinsic electrocatalytic activity and long-term stability for alkaline water oxidation

2021 ◽  
Author(s):  
Venkataramanan Mahalingam ◽  
Gouri Tudu ◽  
Sourav Ghosh ◽  
Sagar Ganguli ◽  
Murthy Koppsetti ◽  
...  
Keyword(s):  
Ethylene Glycol ◽  
Water Splitting ◽  
Nickel Hydroxide ◽  
Oxygen Evolution Reaction ◽  
Water Oxidation ◽  
Electrocatalytic Activity ◽  
One Pot ◽  
Long Term Stability ◽  
Pure Phase

Sustainable electrocatalytic water splitting stipulates development of cheap, efficient and stable electrocatalysts to promote comparatively sluggish oxygen evolution reaction. We have synthesized iron incorporated pure phase α-nickel hydroxide, Ni0.8Fe0.2(OH)2 electrocatalyst...

Determining the Role of Oxygen Vacancies in the Photocatalytic Performance of WO3 for Water Oxidation

2019 ◽  
Author(s):  
Sacha Corby ◽  
Laia Francàs ◽  
Andreas Kafizas ◽  
James R Durrant
Keyword(s):  
Oxygen Vacancy ◽  
Charge Carrier ◽  
Water Oxidation ◽  
Oxygen Vacancies ◽  
Photocatalytic Performance ◽  
Photoelectrochemical Performance ◽  
Solar Water Splitting ◽  
The Impact ◽  
Recombination Kinetics ◽  
Vacancy Concentrations

Oxygen vacancies are common to most metal oxides, whether intentionally incorporated or otherwise, and the study of these defects is of increasing interest for solar water splitting. In this work, we examine nanostructured WO<sub>3</sub> photoanodes of varying oxygen content to determine how the concentration of bulk oxygen-vacancy states affects the photocatalytic performance for water oxidation. Using transient optical spectroscopy, we follow the charge carrier recombination kinetics in these samples, from picoseconds to seconds, and examine how differing oxygen vacancy concentrations impact upon these kinetics. We find that samples with an intermediate concentration of vacancies (~2% of oxygen atoms) afford the greatest photoinduced charge carrier densities, and the slowest recombination kinetics across all timescales studied. This increased yield of photogenerated charges correlates with improved photocurrent densities under simulated sunlight, with both greater and lesser oxygen vacancy concentrations resulting in enhanced recombination losses and poorer J-V performances. Our conclusion, that an optimal – neither too high nor too low – concentration of oxygen vacancies is required for optimum photoelectrochemical performance, is discussed in terms of the impact of these defects on charge separation and transport, as well as the implications held for other highly doped materials for photoelectrochemical water oxidation.

Defective ZnFe2O4 nanorods with oxygen vacancy for photoelectrochemical water splitting

Nanoscale ◽  
2015 ◽  
Vol 7 (45) ◽  
pp. 19144-19151 ◽  
Author(s):  
Ju Hun Kim ◽  
Youn Jeong Jang ◽  
Jin Hyun Kim ◽  
Ji-Wook Jang ◽  
Sun Hee Choi ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Oxygen Vacancy ◽  
Water Splitting ◽  
Water Oxidation ◽  
Oxygen Vacancies ◽  
Electron Donors ◽  
Surface Trap ◽  
Oxidation Activity ◽  
Vacuum Atmosphere ◽  
Photoelectrochemical Water Oxidation

A 1D ZnFe2O4 photoanode is treated under a hydrogen or vacuum atmosphere to improve the photoelectrochemical water oxidation activity up to 20 times. This post-treatment creates oxygen vacancies in the ZnFe2O4 lattice that serve as a source of electron donors and passivates surface trap sites, and as a result improves charge transfer.

Properties, performance and stability of iridium-coated water oxidation electrodes based on anodized titanium felts

2021 ◽  
Author(s):  
André Hofer ◽  
Sebastian Bochmann ◽  
Julien Bachmann
Keyword(s):  
Water Oxidation ◽  
Performance Parameter ◽  
Short Term ◽  
Performance Characterization ◽  
Term Stability ◽  
Long Term Stability ◽  
Anodized Titanium

Holistic performance characterization: not only one performance parameter, but short-term electrocatalytic proficiency in process relevant conditions combined with long-term stability.

scholarly journals Carbon nanomaterials in clean and contaminated soils: environmental implications and applications

2014 ◽  
Vol 1 (1) ◽  
pp. 151-199
Author(s):  
M. J. Riding ◽  
F. L. Martin ◽  
K. C. Jones ◽  
K. T. Semple
Keyword(s):  
Organic Contaminants ◽  
Contaminated Soils ◽  
Carbon Nanomaterials ◽  
Environmental Implications ◽  
Long Term Stability ◽  
Surface Areas ◽  
Hydrophobic Nature ◽  
Highly Hydrophobic ◽  
Case Basis

Abstract. The exceptional sorptive ability of carbon nanomaterials (CNMs) for hydrophobic organic contaminants (HOCs) is driven by their characteristically large reactive surface areas and highly hydrophobic nature. Given these properties, it is possible for CNMs to impact on the persistence, mobility and bioavailability of contaminants within soils, either favourably through sorption and sequestration, hence reducing their bioavailability, or unfavourably through increasing contaminant dispersal. This review considers the complex and dynamic nature of both soil and CNM physicochemical properties to determine their fate and behaviour, together with their interaction with contaminants and the soil micro-flora. It is argued that assessment of CNMs within soil should be conducted on a case-by-case basis, and further work to assess the long-term stability of sorbed contaminants and the toxicity of CNMs is required before their sorptive abilities can be applied to remedy environmental issues.

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