scholarly journals Photocatalytic H2 Evolution, CO2 Reduction, and NOx Oxidation by Highly Exfoliated g-C3N4

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1147
Author(s):  
Nadia Todorova ◽  
Ilias Papailias ◽  
Tatiana Giannakopoulou ◽  
Nikolaos Ioannidis ◽  
Nikos Boukos ◽  
...  
Keyword(s):  
Visible Light ◽  
Specific Surface ◽  
Surface Area ◽  
Photocatalytic Performance ◽  
Uv Light ◽  
Co2 Reduction ◽  
H2 Production ◽  
Thermal Treatments ◽  
H2 Evolution ◽  
Photocatalytic H2 Evolution

g-C3N4, with specific surface area up to 513 m2/g, was prepared via three successive thermal treatments at 550 °C in air with gradual precursor mass decrease. The obtained bulk and exfoliated (1ex, 2ex and 3ex) g-C3N4 were characterized and tested as photocatalysts for H2 production, CO2 reduction and NOx oxidation. The exfoliated samples demonstrated graphene-like morphology with detached (2ex) and sponge-like framework (3ex) of layers. The surface area increased drastically from 20 m2/g (bulk) to 513 m2/g (3ex). The band gap (Eg) increased gradually from 2.70 to 3.04 eV. Superoxide radicals (·O2−) were mainly formed under UV and visible light. In comparison to the bulk, the exfoliated g-C3N4 demonstrated significant increase in H2 evolution (~6 times), CO2 reduction (~3 times) and NOx oxidation (~4 times) under UV light. Despite the Eg widening, the photocatalytic performance of the exfoliated g-C3N4 under visible light was improved too. The results were related to the large surface area and low e−-h+ recombination. The highly exfoliated g-C3N4 demonstrated selectivity towards H2 evolution reactions.

Insight into the factors influencing the photocatalytic H2 evolution performance of molybdenum sulfide

2019 ◽  
Vol 43 (3) ◽  
pp. 1230-1237 ◽  
Author(s):  
Mingcai Yin ◽  
Wenli Zhang ◽  
Hui Li ◽  
Chaojun Wu ◽  
Fangfang Jia ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Photocatalytic Performance ◽  
Molybdenum Sulfide ◽  
H2 Evolution ◽  
Key Factors ◽  
Factors Influencing ◽  
Insight Into ◽  
Photocatalytic H2 Evolution

The specific surface area and composition are found to be the key factors influencing the photocatalytic performance of MoS2+x.

scholarly journals Photodegradation of Rhodamine B in Presence of CaO and NiO-CaO Catalysts

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Tobias Kornprobst ◽  
Johann Plank
Keyword(s):  
Visible Light ◽  
Specific Surface ◽  
Surface Area ◽  
Rhodamine B ◽  
Uv Light ◽  
Mechanistic Study ◽  
Light Conditions ◽  
No Adsorption ◽  
Charged Surfaces ◽  
Positively Charged

A CaO catalyst was prepared by mild calcination (650°C) of facilely precipitated Ca(OH)2and compared to an NiO-CaO catalyst obtained from an Ni(OH)2/Ca(OH)2coprecipitate as a precursor. Both catalysts degraded rhodamine B (RB) effectively when exposed to ultraviolet light but exhibited slower degradation under visible light conditions. Under UV light, CaO was more effective than NiO-CaO, while in visible light, the opposite was observed. A mechanistic study revealed no influence of the specific surface area of the catalysts on RB degradation, no adsorption of RB on the positively charged surfaces of the catalysts, and only incomplete degradation of RB. Consequently, both materials represent nonconventional photocatalysts.

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.

TiO2 composite films on different substrates with enhanced visible light photocatalytic performance

2020 ◽  
Vol 13 (07) ◽  
pp. 2051037
Author(s):  
Ke Han ◽  
Guobao Li ◽  
Fang Li ◽  
Mingming Yao
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Photocatalytic Performance ◽  
Sol Gel ◽  
Composite Films ◽  
Methyl Green ◽  
Photogenerated Electrons

For the sake of improving the photocatalytic performance of TiO2, we prepared the B/Ag/Fe tridoped TiO2 films on common glass and stone substrates by the sol–gel method. In this work, the optical absorption, recombination of photogenerated electrons (e−) and holes (h[Formula: see text]), crystal types, thermal stability, composition, specific surface area and photocatalytic activity of the modified TiO2 films were investigated. The results indicated that B/Ag/Fe tridoping not only enhanced the absorption of visible light by TiO2, but inhibited the recombination of electron–hole (e−/h[Formula: see text]) pairs. The tridoping also promoted the formation of anatase and prevented the transformation of anatase to rutile at high temperature. The composite TiO2 has a large specific surface area, about three times that of pure TiO2. The photocatalytic activity of the TiO2 films were evaluated by methyl green (MG) and formaldehyde degradation. In all samples, the B/Ag/Fe tridoped TiO2 film exhibited the highest degradation rate of MG under both ultraviolet and visible light irradiation. The improvement of photocatalytic performance of TiO2 films is due to the synergistic effect of the B/Ag/Fe tridoping, which enhances the absorption of visible light and prolongs the lifetime of e−/h[Formula: see text] pairs and facilitates transfer of interface charge.

Effect of Rh valence state and doping concentration on the structure and photocatalytic H2 evolution in (Nb,Rh) codoped TiO2 nanorods

Nanoscale ◽  
2020 ◽  
Vol 12 (43) ◽  
pp. 22082-22090
Author(s):  
Jiquan Huang ◽  
Ting Lv ◽  
Qiufeng Huang ◽  
Zhonghua Deng ◽  
Jian Chen ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Visible Light ◽  
Light Absorption ◽  
Valence State ◽  
Doping Concentration ◽  
Photocatalytic Performance ◽  
Tio2 Nanorods ◽  
H2 Evolution ◽  
Visible Light Absorption ◽  
Photocatalytic H2 Evolution

(Nb,Rh) codoped TiO2 nanorods exhibit strong visible light absorption and efficient photocatalytic performance for hydrogen production.

scholarly journals Continuously Improved Photocatalytic Performance of Zn2SnO4/SnO2/Cu2O Composites by Structural Modulation and Band Alignment Modification

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1390 ◽  
Author(s):  
Tiekun Jia ◽  
Junchao An ◽  
Dongsheng Yu ◽  
Jili Li ◽  
Fang Fu ◽  
...  
Keyword(s):  
Visible Light ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Active Sites ◽  
Photocatalytic Performance ◽  
Band Alignment ◽  
Energy Utilization ◽  
Structural Modulation ◽  
Hierarchical Architectures

Improving the photocatalytic performance of multi-component photocatalysts through structural modulation and band alignment engineering has attracted great interest in the context of solar energy utilization and conversion. In our work, Zn2SnO4/SnO2 hierarchical architectures comprising nanorod building block assemblies were first achieved via a facile solvothermal synthesis route with lysine and ethylenediamine (EDA) as directing agents, and then chemically etched in NaOH solution to enlarge the surface area and augment active sites. The etched Zn2SnO4/SnO2 hierarchical architectures were further decorated by Cu2O nanoparticles though an in situ chemical deposition method based on band alignment engineering. In comparison with unetched Zn2SnO4/SnO2, the specific surface area of Zn2SnO4/SnO2/Cu2O hierarchical architectures became larger, and the responsive region and absorbance intensity became wider and higher in the whole visible-light range. Zn2SnO4/SnO2/Cu2O hybrid photocatalysts presented enormously improved visible-light photocatalytic behaviour for Rhodamine B (RhB) decomposition. The enhancement of photocatalytic behaviour was dominantly attributed to the synergy effect of the larger specific surface area, higher light absorption capacity, and more effective photo-induced charge carrier separation and migration. A proposed mechanism for the enormously promoted photocatalytic behaviour is brought forth on the basis of the energy-band structure combined with experimental results.

Coupling of MAPbI3 microcrystals with conductive polyaniline for efficient visible-light-driven H2 evolution

2021 ◽  
Author(s):  
Wenbo Li ◽  
Fang Wang ◽  
Zhengguo Zhang ◽  
Xiaohua Ma ◽  
Shixiong Min
Keyword(s):  
Visible Light ◽  
Charge Separation ◽  
Photocatalytic Performance ◽  
H2 Evolution ◽  
Lead Iodide ◽  
Hybrid Perovskite ◽  
Visible Light Driven ◽  
Conductive Polyaniline ◽  
Methylammonium Lead Iodide ◽  
Photocatalytic H2 Evolution

Although methylammonium lead iodide (MAPbI3) hybrid perovskite has shown great potential in photocatalytic H2 evolution, its photocatalytic performance is significantly suppressed due to the insufficient charge separation. Herein, a strongly...

scholarly journals Charge-Transfer Regulated Visible Light Driven Photocatalytic H2 Production and CO2 Reduction in Tetrathiafulvalene Based Coordination Polymer Gel

2020 ◽  
Author(s):  
Parul Verma ◽  
Pallavi Sarkar ◽  
Ashish Singh ◽  
Swapan Pati ◽  
Tapas Maji
Keyword(s):  
Photocatalytic Activity ◽  
Charge Transfer ◽  
Coordination Polymer ◽  
Visible Light ◽  
Co2 Reduction ◽  
Pt Nanoparticles ◽  
H2 Production ◽  
Polymer Gel ◽  
H2 Evolution

Abstract The much-needed renewable alternatives to fossil fuel can be achieved efficiently and sustainably by converting solar energy to solar fuels via hydrogen generation from water or CO2 reduction. In this regard, a soft processable metal-organic hybrid semiconducting material has been developed and studied for photocatalytic activity towards H2 production and CO2 reduction to CO and CH4 under visible light and direct sunlight irradiation. A tetrapodal low molecular weight gelator is synthesized by integrating tetrathiafulvalene and terpyridine through amide linkage (TPY-TTF). The TPY-TTF acts as a linker and by self-assembly with ZnII results in a charge-transfer (CT) coordination polymer gel (CPG); Zn-TPY-TTF. The Zn-TPY-TTF shows impressive photocatalytic activity towards H2 production (rate = 530 μmol g-1h-1) and CO2 reduction to CO (rate = 438 μmol g-1h-1, selectivity >99%) regulated by charge-transfer interaction. Furthermore, in-situ stabilization of Pt nanoparticles to CPG (Pt@Zn-TPY-TTF) exhibits remarkably enhanced H2 evolution (rate =14727 μmol g-1h-1). Importantly, Pt@Zn-TPY-TTF modulate the CO2 reduction from CO to CH4 (rate = 292 μmol g-1h-1, selectivity >97%). Real-time CO2 reduction reaction is monitored by in-situ DRIFT study and subsequent plausible mechanism is derived computationally. The photocatalytic activity of Zn-TPY-TTF and Pt@Zn-TPY-TTF composite was also examined under sunlight that display excellent H2 evolution and CO2 reduction.

scholarly journals g-C3N4 Sensitized by an Indoline Dye for Photocatalytic H2 Evolution

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1055
Author(s):  
Yihang Chen ◽  
Yanfei Liu ◽  
Zhen Ma
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Water Splitting ◽  
H2 Production ◽  
Charge Carriers ◽  
H2 Evolution ◽  
Co Catalyst ◽  
Efficient Separation ◽  
Photocatalytic H2 Evolution ◽  
Hcl Solution

Protonated g-C3N4 (pCN) formed by treating bulk g-C3N4 with an aqueous HCl solution was modified with D149 dye, i.e., 5-[[4[4-(2,2-diphenylethenyl) phenyl]-1,2,3,3a,4,8b-hexahydrocyclopent[b]indol-7-yl] methylene]-2-(3-ethyl-4-oxo-2-thioxo-5-thiazolidinylidene)-4-oxo-thiazolidin-2-ylidenerhodanine, for photocatalytic water splitting (using Pt as a co-catalyst). The D149/pCN-Pt composite showed a much higher rate (2138.2 µmol·h−1·g−1) of H2 production than pCN-Pt (657.0 µmol·h−1·g−1). Through relevant characterization, the significantly high activity of D149/pCN-Pt was linked to improved absorption of visible light, accelerated electron transfer, and more efficient separation of charge carriers. The presence of both D149 and Pt was found to be important for these factors. A mechanism was proposed.

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