Hexagonal SiC with spatially separated active sites on polar and nonpolar facets achieving enhanced hydrogen production from photocatalytic water reduction

2018 ◽  
Vol 20 (7) ◽  
pp. 4787-4792 ◽  
Author(s):  
Da Wang ◽  
Ning Liu ◽  
Zhongnan Guo ◽  
Wenjun Wang ◽  
Liwei Guo ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Hydrogen Production ◽  
Water Splitting ◽  
Active Sites ◽  
Spatial Separation ◽  
Water Reduction

The spatial separation of the photo-generated electrons and holes between the polar Si-{0001} and non-polar {10−10} crystal facets on 6H-SiC highly improves the photocatalytic activity of water splitting by nearly 5 times.

scholarly journals Hydrogen production from water electrolysis: role of catalysts

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Shan Wang ◽  
Aolin Lu ◽  
Chuan-Jian Zhong
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Noble Metal ◽  
Active Sites ◽  
Current Knowledge ◽  
Low Cost ◽  
Critical Role ◽  
Water Electrolysis ◽  
Efficient Production ◽  
Production Of Hydrogen

AbstractAs a promising substitute for fossil fuels, hydrogen has emerged as a clean and renewable energy. A key challenge is the efficient production of hydrogen to meet the commercial-scale demand of hydrogen. Water splitting electrolysis is a promising pathway to achieve the efficient hydrogen production in terms of energy conversion and storage in which catalysis or electrocatalysis plays a critical role. The development of active, stable, and low-cost catalysts or electrocatalysts is an essential prerequisite for achieving the desired electrocatalytic hydrogen production from water splitting for practical use, which constitutes the central focus of this review. It will start with an introduction of the water splitting performance evaluation of various electrocatalysts in terms of activity, stability, and efficiency. This will be followed by outlining current knowledge on the two half-cell reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), in terms of reaction mechanisms in alkaline and acidic media. Recent advances in the design and preparation of nanostructured noble-metal and non-noble metal-based electrocatalysts will be discussed. New strategies and insights in exploring the synergistic structure, morphology, composition, and active sites of the nanostructured electrocatalysts for increasing the electrocatalytic activity and stability in HER and OER will be highlighted. Finally, future challenges and perspectives in the design of active and robust electrocatalysts for HER and OER towards efficient production of hydrogen from water splitting electrolysis will also be outlined.

scholarly journals Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review

2012 ◽  
Vol 9 (75) ◽  
pp. 2383-2395 ◽  
Author(s):  
Mohammad Mahdi Najafpour ◽  
Fahimeh Rahimi ◽  
Eva-Mari Aro ◽  
Choon-Hwan Lee ◽  
Suleyman I. Allakhverdiev
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Water Oxidation ◽  
Active Sites ◽  
Manganese Oxides ◽  
Metal Compounds ◽  
Functional Models ◽  
Current Densities ◽  
Conversion Efficiencies ◽  
Manganese Compounds

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese–calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups.

Nonaqueous synthesis of TiO2–carbon hybrid nanomaterials with enhanced stable photocatalytic hydrogen production activity

2015 ◽  
Vol 3 (18) ◽  
pp. 10060-10068 ◽  
Author(s):  
Yijun Yang ◽  
Ye Yao ◽  
Liu He ◽  
Yeteng Zhong ◽  
Ying Ma ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Hydrogen Production ◽  
Water Splitting ◽  
Hybrid Nanomaterials ◽  
Photocatalytic Hydrogen Production ◽  
Production Activity ◽  
Nonaqueous Synthesis

Enhanced and stable photocatalytic activity upon water splitting was demonstrated in a series of TiO2–carbon hybrid nanomaterials, which were derived from oleylamine wrapped ultrathin TiO2 nanosheets.

Photocatalytic activity of ZrO2 composites with graphitic carbon nitride for hydrogen production under visible light

2019 ◽  
Vol 43 (11) ◽  
pp. 4455-4462 ◽  
Author(s):  
Mohammed Ismael ◽  
Ying Wu ◽  
Michael Wark
Keyword(s):  
Photocatalytic Activity ◽  
Hydrogen Production ◽  
Visible Light ◽  
Water Splitting ◽  
Carbon Nitride ◽  
Graphitic Carbon Nitride ◽  
Superior Performance ◽  
Electron Hole ◽  
Effective Electron ◽  
Composite Interface

The synthesized ZrO2/g-C3N4 composites exhibit superior performance in water splitting for hydrogen production due to the effective electron–hole separation at the composite interface.

In situ Synthesis of Nickel-Dimethylglyoxime/Black Phosphorus Nanorods for Photocatalytic Hydrogen Production from Water Splitting

NANO ◽  
2020 ◽  
Vol 15 (10) ◽  
pp. 2050125
Author(s):  
Hui’e Wang
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Active Sites ◽  
Hydrogen Generation ◽  
Hollow Structure ◽  
Black Phosphorus ◽  
In Situ Growth ◽  
Photocatalytic Hydrogen Production ◽  
Reaction Cycles

Here, a novel material consisting of black phosphorus (BP) and nickel-dimethylglyoxime nanorods was successfully prepared via a facile in situ calcination strategy, which possesses efficient catalytic activity for hydrogen production from water splitting. The reason for this phenomenon was explained by a series of characterization technologies such as SEM, TEM, XRD, UV–Vis, XPS and photoelectrochemical. We demonstrated that the fast e− transport channels were provided by the formed hollow structure of C@Ni-D nanorods, the highly exposed active sites on C@Ni-BP nanorods benefiting from the direct in situ growth of BP, the resulted synergetic effects of C@Ni-D-2 nanorods and BP achieved a better performance of photocatalytic hydrogen production from water splitting. The optimal hydrogen generation of C@Ni-BP-2 nanorods could reach up to 600[Formula: see text][Formula: see text]mol within 180[Formula: see text]min and the rate of hydrogen production did not decrease significantly after four repeated reaction cycles. This work may offer new direction in situ growth of novel catalysts for achieving highly efficient hydrogen production.

scholarly journals Photocatalytic Hydrogen Evolution from Water Splitting Using Core-Shell Structured Cu/ZnS/COF Composites

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3380
Author(s):  
Wenmin Wang ◽  
Bing Li ◽  
Hsin-Ju Yang ◽  
Yuzhi Liu ◽  
Lakshmanan Gurusamy ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Active Sites ◽  
Fossil Fuels ◽  
High Energy ◽  
High Energy Density ◽  
Core Shell ◽  
Porous Network ◽  
Photocatalytic Hydrogen Production ◽  
Redox Sites

Hydrogen is considered to be a very efficient and clean fuel since it is a renewable and non-polluting gas with a high energy density; thus, it has drawn much attention as an alternative fuel, in order to alleviate the issue of global warming caused by the excess use of fossil fuels. In this work, a novel Cu/ZnS/COF composite photocatalyst with a core-shell structure was synthesized for photocatalytic hydrogen production via water splitting. The Cu/ZnS/COF microspheres formed by Cu/ZnS crystal aggregation were covered by a microporous thin-film COF with a porous network structure, where COF was also modified by the dual-effective redox sites of C=O and N=N. The photocatalytic hydrogen production results showed that the hydrogen production rate reached 278.4 µmol g−1 h−1, which may be attributed to its special structure, which has a large number of active sites, a more negative conduction band than the reduction of H+ to H2, and the ability to inhibit the recombination of electron-hole pairs. Finally, a possible mechanism was proposed to effectively explain the improved photocatalytic performance of the photocatalytic system. The present work provides a new concept, in order to construct a highly efficient hydrogen production catalyst and broaden the applications of ZnS-based materials.

scholarly journals Covalent organic frameworks in Lieb lattice for tunable photocatalytic water splitting under visible light

2021 ◽  
Author(s):  
Hongde Yu ◽  
Dong Wang
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Active Sites ◽  
Rational Design ◽  
Near Infrared ◽  
Band Alignment ◽  
Covalent Organic Frameworks ◽  
Photocatalytic Water Splitting ◽  
Metal Free ◽  
Lieb Lattice

Covalent organic frameworks (COFs) with highly designable skeleton and inherent pores have emerged as promising organic photocatalysts for hydrogen production. However, inefficient solar light harvesting, strong excitonic effect, and the lack of active sites still pose major challenges to the rational design of COFs for efficient photocatalytic water splitting and the structure-property relationship has not been established. In this work, we investigated the fundamental mechanism of photoelectrochemical conversion in fully conjugated donor (D)-acceptor (A) COFs in Lieb lattice and proposed a facile strategy to achieve broad visible and near-infrared absorption, prompt exciton dissociation, tunable band alignment for overall water splitting, and metal-free catalysis of hydrogen production. Interestingly, we found that the exciton binding energy was substantially reduced with the narrowing of optical band gap and the increase of static dielectric constant. Further, we unraveled that the hydrogen bond played a vital role in suppressing the overpotential for hydrogen evolution reaction to enable metal-free catalysis. These findings not only highlight a novel route to modulating electronic properties of COFs towards high photocatalytic activity for water splitting, but also offer tremendous opportunities to design metal-free catalysts for other chemical transformations.

Photocatalytic Activity of Ce-Doped Hematite for Hydrogen Production

2014 ◽  
Vol 787 ◽  
pp. 46-51 ◽  
Author(s):  
Jia Jia Cai ◽  
Song Li ◽  
Jian Sheng Wang ◽  
Yu Dong Mei ◽  
Yu Ping Ren ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Hydrogen Production ◽  
Visible Light ◽  
Thermal Oxidation ◽  
Water Splitting ◽  
Carrier Density ◽  
Oxidation Treatment

Hematite is one of the most promising photoanodes for water splitting, but its photoelectrochemical (PEC) efficiency is still low. This work proved that the PEC efficiency of hematite can be improved by Ce doping. The Ce doped hematite was successfully prepared by co-sputtering CeO2 and Fe2O3, and followed by thermal oxidation treatment. The results of J-V test showed that the photocurrent of 5 at.% Ce doped α-Fe2O3 film can reached 1.35mA/cm2 in 1 M NaOH (pH=13.6) at 1.23V vs. NHE, which is nearly 15 times higher than the undoped one. The enhancement of PEC efficiency was proved by the enhancement of absorbance of visible light, as well as increased carrier density after Ce doping.

The enhanced photocatalytic activity of g-C3N4-LaFeO3 for the water reduction reaction through a mediator free Z-scheme mechanism

2017 ◽  
Vol 4 (6) ◽  
pp. 1022-1032 ◽  
Author(s):  
S. Acharya ◽  
S. Mansingh ◽  
K. M. Parida
Keyword(s):  
Photocatalytic Activity ◽  
Hydrogen Production ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Reduction Reaction ◽  
Light Irradiation ◽  
Water Reduction ◽  
Solid Interface

A g-C3N4/LaFeO3 solid–solid interface showing enhanced hydrogen production ability under visible-light irradiation through a mediator free Z-Scheme mechanism.

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