scholarly journals Electrocatalytic H2 Evolution Promoted by a Bioinspired (N2S2)Ni(II) Complex at Low Acid Concentration

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Liviu M. Mirica
Keyword(s):  
Acid Concentration ◽  
H2 Production ◽  
Turnover Frequency ◽  
H2 Evolution ◽  
Electrochemical Mechanism

We have investigated a bioinspired (N2S2)Ni(II) electrocatalyst that produces H2 from CF3CO2H with a turnover frequency (TOF) of ~200,000 s–1 at low acid concentration (<0.043 M) in MeCN. We also propose an electrochemical mechanism for such an electrocatalyst toward H2 production and benchmarked its activity by comparing its TOF and overpotential with those of other reported molecular Ni H2 evolution electrocatalysts.

Electrocatalytic H2 evolution promoted by a bioinspired (N2S2)Ni(II) complex

2022 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Liviu M. Mirica
Keyword(s):  
Acid Concentration ◽  
Turnover Frequency ◽  
H2 Evolution

We have investigated a bioinspired (N2S2)Ni(II) electrocatalyst that produces H2 from CF3CO2H with a turnover frequency (TOF) of ~1,250 s–1 at low acid concentration (<0.043 M) in MeCN. A mechanism...

CdSe Quantum Dots/White Graphene Hexagonal Porous Boron Nitride Sheet (h-PBNs) Heterostructure Photocatalyst for Solar Driven H2 Production

2021 ◽  
Author(s):  
Raheman Shakeelur ◽  
Rupali S. Mane ◽  
Higgins Wilson ◽  
Neetu Jha
Keyword(s):  
Active Site ◽  
Charge Separation ◽  
High Surface ◽  
High Surface Area ◽  
H2 Production ◽  
H2 Evolution ◽  
The World ◽  
2D Nanomaterials ◽  
White Graphene ◽  
Photogenerated Charge Separation

In the world of photocatalytic hydrogen (H2) evolution two-dimensional (2D) nanomaterials have attracted widespread attention owing to their high surface area, abundant active site, and excellent photogenerated charge separation properties....

scholarly journals Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1523 ◽  
Author(s):  
Arnaud Igor Ndé-Tchoupé ◽  
Rui Hu ◽  
Willis Gwenzi ◽  
Achille Nassi ◽  
Chicgoua Noubactep
Keyword(s):  
Metallic Iron ◽  
Environmental Remediation ◽  
Material Selection ◽  
H2 Production ◽  
H2 Evolution ◽  
Solution Ph ◽  
Neutral Ph ◽  
Uranium Removal ◽  
Initial Reactivity

Metallic iron (Fe0) has been demonstrated as an excellent material for decentralized safe drinking water provision, wastewater treatment and environmental remediation. An open issue for all these applications is the rational material selection or quality assurance. Several methods for assessing Fe0 quality have been presented, but all of them are limited to characterizing its initial reactivity. The present study investigates H2 evolution in an acidic solution (pH 2.0) as an alternative method, while comparing achieved results to those of uranium removal in quiescent batch experiments at neutral pH values. The unique feature of the H2 evolution experiment is that quantitative H2 production ceased when the pH reached a value of 3.1. A total of twelve Fe0 specimens were tested. The volume of molecular H2 produced by 2.0 g of each Fe0 specimen in 560 mL H2SO4 (0.01 M) was monitored for 24 h. Additionally, the extent of U(VI) (0.084 mM) removal from an aqueous solution (20.0 mL) by 0.1 g of Fe0 was characterized. All U removal experiments were performed at room temperature (22 ± 2 °C) for 14 days. Results demonstrated the difficulty of comparing Fe0 specimens from different sources and confirmed that the elemental composition of Fe0 is not a stand-alone determining factor for reactivity. The time-dependent changes of H2 evolution in H2SO4 confirmed that tests in the neutral pH range just address the initial reactivity of Fe0 materials. In particular, materials initially reacting very fast would experience a decrease in reactivity in the long-term, and this aspect must be incorporated in designing novel materials and sustainable remediation systems. An idea is proposed that could enable the manufacturing of intrinsically long-term efficient Fe0 materials for targeted operations as a function of the geochemistry.

scholarly journals Enhanced Photocatalytic Hydrogen Production of the Polyoxoniobate Modified with RGO and PPy

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2449
Author(s):  
Shiliang Heng ◽  
Lei Li ◽  
Weiwei Li ◽  
Haiyan Li ◽  
Jingyu Pang ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Active Sites ◽  
High Efficiency ◽  
Solvothermal Method ◽  
H2 Production ◽  
H2 Evolution ◽  
Co Catalyst ◽  
Photocatalytic Hydrogen Production ◽  
Reduced Graphene ◽  
One Step

The development of high-efficiency, recyclable, and inexpensive photocatalysts for water splitting for hydrogen production is of great significance to the application of solar energy. Herein, a series of graphene-decorated polyoxoniobate photocatalysts Nb6/PPy-RGO (Nb6 = K7HNb6O19, RGO = reduced graphene oxide, PPy = polypyrrole), with the bridging effect of polypyrrole were prepared through a simple one-step solvothermal method, which is the first example of polyoxoniobate-graphene-based nanocomposites. The as-fabricated photocatalyst showed a photocatalytic H2 evolution activity without any co-catalyst. The rate of 1038 µmol g−1 in 5 h under optimal condition is almost 43 times higher than that of pure K7HNb6O19·13H2O. The influencing factors for photocatalysts in photocatalytic hydrogen production under simulated sunlight were studied in detail and the feasible mechanism is presented in this paper. These results demonstrate that Nb6O19 acts as the main catalyst and electron donor, RGO provides active sites, and PPy acted as an electronic bridge to extend the lifetime of photo-generated carriers, which are crucial factors for photocatalytic H2 production.

Influence of Ru(II) Bipyridyl Complex on the Photocatalytic H2 Evolution over TiO2 Nanoparticles with Mesostructures

2008 ◽  
Vol 47-50 ◽  
pp. 825-828 ◽  
Author(s):  
Tian You Peng ◽  
Ding Ning Ke ◽  
Chun Wu ◽  
Cai Ping ◽  
Liang Ma ◽  
...  
Keyword(s):  
Visible Light ◽  
Dynamic Equilibrium ◽  
H2 Production ◽  
Electron Donors ◽  
H2 Evolution ◽  
Conjugation System ◽  
Antenna Effect ◽  
Dye Sensitized ◽  
Sensitization Process ◽  
Bipyridyl Complex

H2 production over dye-sensitized Pt/TiO2 nanoparticles with mesostructures under visible light was investigated by using methanol as electron donors. Three types of Ru(II) bipyridyl complexes, which can be attached to Pt/m-TiO2 with different linkage modes, show different photosensitization. The dye tightly linked with m-TiO2 has better durability but the lowest H2 evolution efficiency, whereas the loosely attached dyes possess higher H2 evolution efficiency and preferable durability. It seems that the dynamic equilibrium between the linkage of ground state dye with TiO2 and the divorce of oxidization state dye from the surfaces plays a crucial role in the photochemical behavior during photocatalyst sensitization process. The binuclear Ru(II) shows a better photosensitization in comparison with mono- nuclear Ru(II) dyes due to its large conjugation system and “antenna effect”, which, in turn, improve the visible light harvesting and electron transfer between the dye and TiO2.

scholarly journals Construction of K+ ions gradient in crystalline carbon nitride to accelerate charge separation for efficient visible light H2 production

2021 ◽  
Author(s):  
Guoqiang Zhang ◽  
Yangsen Xu ◽  
Chuan-Xin He ◽  
Yongliang Li ◽  
Xiangzhong Ren ◽  
...  
Keyword(s):  
Visible Light ◽  
Driving Force ◽  
Carbon Nitride ◽  
Photocatalytic Performance ◽  
H2 Production ◽  
H2 Evolution ◽  
Concentration Gradients ◽  
Diffusion Controlled ◽  
Activity Enhancement ◽  
First Time

Abstract Like most of the recent reported semiconductor photocatalysts, the sluggish dynamic charges transfer and separation caused by weak driving force still restricts the further improvement of photocatalytic performance in crystalline carbon nitride (CCN). Here, we successfully prepared a series of heptazine-based K+ implanted CCN (KCN) for the first time, where the K+ ions concentration was gradiently inserted through controlling its diffusion from the surface to bulk in carbon nitride (CN). As a powerful driving force, the built-in electric field (BIEF) induced by this concentration gradient, greatly accelerates the drift movement and the transport from bulk to the surface, as well as the separation of photogenerated carriers. Consequently, the KCN with optimized BIEF displays a ～34 times promotion than original CN for visible-light H2 evolution. Such a high activity enhancement factor is at a relatively good level in reported CCN. Our proposed strategy to induce BIEF production by constructing concentration gradients through thermodynamically feasible diffusion controlled solid-state reaction, can be adopted to build other efficient photocatalytic systems.

scholarly journals Histidine Decorated Nanoparticles of CdS for Highly Efficient H2 Production via Water Splitting

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3738
Author(s):  
Fumiya Tojo ◽  
Manabu Ishizaki ◽  
Shigeru Kubota ◽  
Masato Kurihara ◽  
Fumihiko Hirose ◽  
...  
Keyword(s):  
Cadmium Sulfide ◽  
Water Splitting ◽  
Solvothermal Method ◽  
H2 Production ◽  
Sem Analysis ◽  
Cds Nanoparticles ◽  
H2 Evolution ◽  
X Ray Diffraction ◽  
Hexagonal Wurtzite Crystal Structure ◽  
Xrd Patterns

Pure cadmium sulfide and histidine decorated cadmium sulfide nanocomposites are prepared by the hydrothermal or solvothermal method. Scanning electron microscopy (SEM) analysis shows that the particle sizes of pure cadmium sulfide (pu/CdS) and histidine decorated cadmium sulfide prepared by the hydrothermal method (hi/CdS) range from 0.75 to 3.0 μm. However, when a solvothermal method is used, the particle size of histidine decorated cadmium sulfide (so/CdS) ranges from 50 to 300 nm. X-ray diffraction (XRD) patterns show that all samples (pu/CdS, hi/CdS and so/CdS) have a hexagonal wurtzite crystal structure but so/CdS has a poor crystallinity compared to the others. The as-prepared samples are applied to photocatalytic hydrogen production via water splitting and the results show that the highest H2 evolution rate for pu/CdS and hi/CdS are 1250 and 1950 μmol·g−1·h−1, respectively. On the other hand, the so/CdS sample has a rate of 6020 μmol·g−1·h−1, which is about five times higher than that of the pu/CdS sample. The increased specific surface area of so/CdS nanoparticles and effective charge separation by histidine molecules are attributed to the improved H2 evolution.

scholarly journals Pt Deposites on TiO2 for Photocatalytic H2 Evolution: Pt Is Not Only the Cocatalyst, but Also the Defect Repair Agent

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1047 ◽  
Author(s):  
Zhan Shu ◽  
Yandi Cai ◽  
Jiawei Ji ◽  
Changjin Tang ◽  
Shuohan Yu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Charge Separation ◽  
H2 Production ◽  
H2 Evolution ◽  
X Ray ◽  
Production Activity ◽  
Defect Repair ◽  
New Perspective ◽  
Photocatalytic H2 Evolution

Pt, as a common cocatalyst, has been widely used in photocatalytic H2 evolution. However, the specific role of Pt in photocatalytic H2 evolution has not been thoroughly studied. In this paper, by employing three Pt sources with different charges (positive, negative and neutral), we systematically studied the charge effect of Pt sources on photocatalytic H2 evolution via TiO2 catalyst. According to the results of Raman, X-ray photoelectron spectroscopy (XPS), recycle experiments and photocurrent characterizations, it was found that TiO2 would produce electropositive defects during photocatalytic H2 evolution, inevitably leading to the decline of H2 production activity. Thanks to the electrostatic interaction, the electronegative Pt source not only promoted charge separation, but preferential deposited on electropositive defects, which acted as the defect repair agent, and thus resulted in the increased photocatalytic stability. This work may provide a new perspective for enhancing photocatalytic stability of hydrogen production.

scholarly journals Reduction of cyclopropene by NifV- and wild-type nitrogenases from Klebsiella pneumoniae

1989 ◽  
Vol 258 (2) ◽  
pp. 487-491 ◽  
Author(s):  
J P Gemoets ◽  
M Bravo ◽  
C E McKenna ◽  
G J Leigh ◽  
B E Smith
Keyword(s):  
Klebsiella Pneumoniae ◽  
Azotobacter Vinelandii ◽  
Electron Flux ◽  
H2 Production ◽  
Relative Increase ◽  
Analogous Reaction ◽  
Wild Type ◽  
H2 Evolution ◽  
Product Ratio ◽  
In The Wild

The nitrogenase from wild-type Klebsiella pneumoniae reduces cyclopropene to cyclopropane and propene in the ratio 1:2 at pH 7.5. We show in this paper that the nitrogenase from a nifV mutant of K. pneumoniae also reduces cyclopropene to cyclopropane and propene, but the ratio of products is now 1:1.4. However, both nitrogenases exhibit the same Km for cyclopropene (2.1 x 10(4) +/- 0.2 x 10(4) Pa), considerably more than the Km for the analogous reaction with Azotobacter vinelandii nitrogenase under the same conditions (5.1 x 10(3) Pa). Analysis of the data shows that the different product ratio arises from the slower production of propene compared with cyclopropane by the mutant nitrogenase. During turnover, both nitrogenases use a large proportion of the electron flux for H2 production. CO inhibits the reduction of cyclopropene by both K. pneumoniae proteins, but the mutant nitrogenase exhibits 50% inhibition at approx. 10 Pa, whereas the corresponding value for the wild-type nitrogenase is approx. 110 Pa. However, H2 evolution by the mutant enzyme is much less affected than is cyclopropene reduction. CO inhibition of cyclopropene reduction by the nitrogenases coincides with a relative increase in H2 evolution, so that in the wild-type (but not the mutant) the electron flux is approximately maintained. The cyclopropane/propene production ratios are little affected by the presence of CO within the pressure ranges studied at least up to 50% inhibition.

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