Selective charge transfer to dioxygen on KPF₆-modified carbon nitride for photocatalytic synthesis of H₂O₂ under visible light

Kim, Sujeong,Moon, Gun-hee,Kim, Hyejin,Mun, Yeongdong,Zhang, Peng,Lee, Jinwoo,Choi, Wonyong Academic Press 2018 Journal of catalysis Vol.357 No.-

<P><B>Abstract</B></P> <P>Photochemical production of H<SUB>2</SUB>O<SUB>2</SUB> through O<SUB>2</SUB> reduction has been proposed as an alternative method of solar energy storage. A carbon nitride (CN) photocatalyst was selected for this purpose. The incorporation of KPF<SUB>6</SUB> into the CN structure greatly enhanced the apparent quantum yield (AQY) of H<SUB>2</SUB>O<SUB>2</SUB> production in the UV and visible light region. The AQY of KPF<SUB>6</SUB>-modified CN was measured to be 35.9% and 24.3% under monochromatic irradiation at 370 and 420 nm, respectively, which are 8.3 and 26.1 times higher than for bare CN. The KPF<SUB>6</SUB>-enhanced activity is ascribed to several factors including (i) enhanced absorption of UV and visible light, (ii) higher charge carrier density, (iii) retarded radiative recombination of charge pairs, (iv) highly selective two-electron transfer to O<SUB>2</SUB>, and (v) hindered photodecomposition of in-situ generated H<SUB>2</SUB>O<SUB>2</SUB>. The markedly high selectivity of KPF<SUB>6</SUB>-modified CN toward the two-electron reduction of O<SUB>2</SUB> (leading to H<SUB>2</SUB>O<SUB>2</SUB>) was demonstrated in comparision with other photoreductive conversions such as the reduction of polyoxometalate (POM → POM<SUP>−</SUP>), hexavalent chromium (Cr<SUP>VI</SUP> → Cr<SUP>III</SUP>), CCl<SUB>4</SUB> (dechlorination), and protons (H<SUB>2</SUB> production). This study developed a simple method of efficient production of H<SUB>2</SUB>O<SUB>2</SUB> using visible light, which could be utilized for a variety of applications that employ H<SUB>2</SUB>O<SUB>2</SUB> as a solar fuel or a green oxidant.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The photocatalytic production of H<SUB>2</SUB>O<SUB>2</SUB> was markedly enhanced by the incorporation of KPF<SUB>6</SUB> into the carbon nitride (CN) structure. </LI> <LI> The highest quantum yields of the production of H<SUB>2</SUB>O<SUB>2</SUB> were achieved using KPF<SUB>6</SUB>-modified CN (35.9% and 24.3% at 370 and 420 nm, respectively). </LI> <LI> KPF<SUB>6</SUB>-modified CN exhibited markedly high selectivity for two-electron reduction of O<SUB>2</SUB> to produce H<SUB>2</SUB>O<SUB>2</SUB>. </LI> <LI> The present catalytic system consisting of earth-abundant elements utilizes only visible light and dioxygen without using any noble metal catalysts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

AgI/AgCl/H2WO4 Double Heterojunctions Composites: Preparation and Visible-Light Photocatalytic Performance

Chunping Liu,Haili Lin,Shanmin Gao,Ping Yin,Lei Guo,Baibiao Huang,Ying Dai 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.2

AgI/AgCl/H2WO4 double heterojunctions photocatalyst was prepared via deposition-precipitation followed by ion exchange method. The structure, crystallinity, morphology, chemical content and other physical-chemical properties of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectra (EDX), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL). The photocatalytic activity of the AgI/AgCl/H2WO4 was evaluated by degrading methyl orange (MO) under visible light irradiation (λ> 400 nm). The double heterojunctions photocatalyst displayed more efficient photocatalytic activity than pure AgI, AgCl, H2WO4 and AgCl/H2WO4. Based on the reactive species and energy band structure, the enhanced photocatalytic activity mechanism of AgI/AgCl/H2WO4 was discussed in detail. The improved photocatalytic performance of AgI/AgCl/H2WO4 double heterojunctions could be ascribed to the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs, which was in close relation with the AgI/AgCl/H2WO4 heterojunctions formed between AgI, AgCl and H2WO4.

Ratio Dependence of the Visible Light Photocatalytic Efficiency for Zn_2Ti_(0.9)Cr_yFe_([0.1]-y)O_4: Cr/Fe (0.02 < y < 0.08) Photocatalyst Synthesized by Using a Solid State Reaction Method

Pramod H. Borse,조채용,K. T. Lim,Y. J. Lee,배종성,정의덕,H. G. Kim 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1

We synthesized four different photocatalyst systems viz. Zn_2TiO_4, Zn_2Ti_(1-x)Fe_xO_4, Zn_2Ti_(1-x)Cr_xO_4 (0 ≤ x < 0.8) and Zn_2Ti_(0.9)Cr_yFe_([0.1]-y)O_4 (0.022TiO<SUB>4</SUB> was converted to visible light active material by controlled doping/co-doping of Cr and Fe metal-ions at Ti substitutional site. We investigated their structural, optical and photocatalytic water decomposition property. The co-doping induces strong absorption bands in visible region (at λ~ 480 nm and λ~ 620 nm) in the host band gap. The optimum system of Zn_2Ti_(0.9)Cr_(0.05)Fe_(0.05)O_4 yielded maximum H<SUB>2</SUB> generation. In contrast to the visible light inactivity of Fe and Cr doped Zn_2TiO_4, the H_2 production under visible light irradiation from co-doped samples, increased till the optimum ‘y’ value. Consequently, there exists an optimized co-dopant concentration for efficient photocatalytic hydrogen production under visible light (λ ≥ 420 nm).

Efficient solar-light photocatalytic H2 evolution of Mn0.5Cd0.5S coupling with S,N-codoped carbon

Hao Peng,Congying Huang,Xiaogang Zheng,Jing Wen 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.106 No.-

The low-cost and highly-efficient photocatalysts for solar-light induced water splitting had drawn greatattention to develop the renewable hydrogen economy. To enhance the solar-light driven H2 evolution ofMn0.5Cd0.5S, Mn0.5Cd0.5S was modified by S,N-codoped carbon (3-MCS/SN-C) via the in-situ sulfurizationat high temperature. In contrast with Mn0.5Cd0.5S (11.13 mmol g1 h1) and S-doped g-C3N4(0.35 mmol g1 h1), the optimal 3-MCS/SN-C with a mass ratio of Mn0.5Cd0.5S to S,N-codoped carbonof 1:3 exhibited the best H2 evolution rate of 27.58 mmol g1 h1 and an apparent quantum yield of27.43% at 400 nm. The photo-corrosion induced to the decreased H2 evolution capacity of 3-MCS/SN-Cfrom 131.13 to 126.52 mmol g1 after five cycles of 5 h. S,N-codoped carbon could efficiently capture visiblelight and absorb the photons, leading to the efficient transformation and separation of photogeneratedcarriers at the junction interface between Mn0.5Cd0.5S and S,N-codoped carbon.

An S-scheme photocatalyst constructed by modifying Ni-doped Sn3O4 micro-flowers on g-C3N4 nanosheets for enhanced visible-light-driven hydrogen evolution

Dandan Wang,Zhaoxin Lin,Chun Miao,Wei Jiang,Hongji Li,Chunbo Liu,Guangbo Che 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.113 No.-

Carbon nitrides (g-C3N4) is considered to be the prospective semiconductor photocatalyst for photocatalytic H2 evolution. Nevertheless, it suffers from low charge transfer efficiency and fewer metal active sites. Thereby, Ni-Sn3O4/g-C3N4 photocatalysts were constructed by anchoring Ni-doped Sn3O4 micro-flowers on g-C3N4 via a feasible and straightforward solvothermal treatment. The prepared Ni-Sn3O4/g-C3N4 S-scheme heterojunction could improve the transfer and separation efficiency of photo-generated electron-hole pairs by facilitating the electrons transfer from Ni-Sn3O4 to g-C3N4. Moreover, the photocatalytic H2 production performance was ameliorated due to the established internal electric field and the energy band bending in Ni-Sn3O4/g-C3N4 S-scheme heterojunction. Meanwhile, the doping Ni in Sn3O4 exposed more active sites in Ni-Sn3O4/g-C3N4 heterojunction for producing H2. As a result, Ni-Sn3O4/g-C3N4-5 photocatalyst exhibited outstanding H2 yields of 1961 µmol h−1 g−1 under visible light irradiation in comparison with pure Ni-Sn3O4 (12 µmol h−1 g−1) and bared g-C3N4 (1391 µmol h−1 g−1). Furthermore, the S-scheme mechanism in Ni-Sn3O4/g-C3N4 heterojunction for producing H2 by oxidizing H2O was proposed. This study provides helpful guide for developing efficient g-C3N4-based photocatalytic systems.

UV-light-activated H₂S gas sensing by a TiO₂ nanoparticulate thin film at room temperature

Chinh, Nguyen Duc,Kim, Chunjoong,Kim, Dojin Elsevier 2019 Journal of Alloys and Compounds Vol.778 No.-

<P><B>Abstract</B></P> <P>A UV-light-activated TiO<SUB>2</SUB> thin film gas sensor composed of nanoparticles is reported for H<SUB>2</SUB>S detection at room temperature. TiO<SUB>2</SUB> nanoparticulate thin films were fabricated by bar coating of a mixture of TiO<SUB>2</SUB> powder and acetic acid. The morphology and structural properties of the films were examined by scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy, and absorption spectroscopy. The nil response to H<SUB>2</SUB>S was significantly enhanced by UV light irradiation in the response levels and response/recovery kinetics. The effect of the sensor conductance and light intensity towards sensor optimization was discussed. The sensor exhibited high gas selectivity, repeatability, and linearity for practical applications of the sensor, but the interference of humidity on the sensing process needs to be solved. The results exhibited a simple way to detect parts per million concentrations of H<SUB>2</SUB>S at room temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanoparticulate TiO<SUB>2</SUB> thin film was fabricated by a cost-effective method of bar coating. </LI> <LI> H<SUB>2</SUB>S sensing at room temperature under UV irradiation satisfying the sensor. </LI> <LI> Analysis of the response-recovery kinetics under UV irradiation at RT. </LI> </UL> </P>

Investigation of the Physico-chemical Properties of Sr2FeNb1−xWxO6 (0.0 ≤ x ≤ 0.1) for Visible-light Photocatalytic Water-splitting Applications

P. H. Borse,K. T. Lim,J.H. Yoon,배종성,M. G. Ha,E. H. Chung,정의덕,김현규 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.2

Incorporation of the pentavalent W-ion has been investigated in Sr2FeNb1−xWxO6 for 0.0 ≤ x< 0.15. The synthesized double perovskite system was used to study its structural and opticalproperties. The optical, as well as structural, properties were found to change with the varyingNb:W stoichiometric ratio. The Sr2FeNb1−xWxO6 samples with 0.0 ≤ x < 0.1 were furtherinvestigated for visible-light photocatalytic water splitting. At an optimized value of x ∼0.01,i.e., Sr2FeNb0.99W0.01O6, the perovskite lattice yielded an efficient photocatalyst, it displayed amoderately-altered direct band-gap of 2.17 eV, and gave twice the higher quantum yield for photosplittingin a H2O-CH3OH mixture compared to that for x ∼0 under visible light (λ ≥ 420 nm). For x > 0.1, the Sr2FeNb1−xWxO6 showed no change in the optical properties but crystal structurewas drastically affected , exhibiting impurity phases and a disordered structure, thus yielding a degradedphotocatalytic behavior. The higher absorption coefficient in the Sr2FeNb0.99W0.01O6 anda higher electron-density acquired by n-type lattice doping seems to be responsible for the betterefficient charge separation in Sr2FeNb1−xWxO6 (0.01 ≤ x ≤ 0.20) and consequently the higherphotocatalytic activity in co-catalyst loaded photocatalysts.

Solar light response with noble metal-free highly active copper(II) phosphate/titanium dioxide nanoparticle/copper(II) oxide nanocomposites for photocatalytic hydrogen production

Mandari, Kotesh Kumar,Do, Jeong Yeon,Vattikuti, S.V. Prabhakar,Police, Anil Kumar Reddy,Kang, Misook Elsevier 2018 Journal of alloys and compounds Vol.750 No.-

<P><B>Abstract</B></P> <P>A novel Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TiO<SUB>2</SUB> nanoparticle (TNP)/CuO nanocomposite with an excellent natural solar-light-driven photocatalytic H<SUB>2</SUB> production performance was synthesized using a sol-gel method. The 1%Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO catalyst displayed a better photocatalytic H<SUB>2</SUB> production yield (59.5 mmolg<SUP>−1</SUP>; natural solar light; 151 times higher than that of TNP under the optimal conditions; catalyst dosage of 0.010 g and 5% aqueous glycerol concentration) than TNP, CuO/TNP, Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP, and various Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> loadings in the Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO catalysts. The improved photocatalytic H<SUB>2</SUB> yields could be attributed to a suppressed recombination of charge carriers, preferable visible absorption ability, crystallinity, strong interactions, and high surface areas of 1%Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO, which were confirmed using X-ray diffraction, temperature programmed reduction, diffuse reflectance spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, Brunauer-Emmett-Teller surface area analysis, elemental mapping, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Raman spectroscopy, photoluminescence, and photocurrent techniques. The 1%Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO catalyst could also contribute to the enhanced photostability and recyclability towards the photocatalytic hydrogen production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO nanocomposites were prepared by sol-gel method. </LI> <LI> Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>/TNP/CuO shows enhanced visible absorption and inhibit the recombination. </LI> <LI> Strong interaction between Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> and/or CuO nanoclusters with TNP by H<SUB>2</SUB>-TPR. </LI> <LI> Synergetic effect of Cu<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>, CuO and TNP displayed effective redox reactions. </LI> <LI> Optimum H<SUB>2</SUB> yields obtained 59.5 mmol g<SUP>−1</SUP>, 151 times toTNP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

스타티스 '오션 블루'의 자가영양배양시 광도, 환기횟수 및 CO2 농도가 소식물체의 기내 생육에 미치는 영향

정기원,정병룡 (사) 한국생물환경조절학회 2002 생물환경조절학회지 Vol.11 No.3

Growth and development of Limonium spp. cean Blueplantlets were studied under, three levelsof photosynthetic photon flux (PPF), 70, 150 and 220mmol m-2 s-1, two levels of CO2 concentration,500 and 1000 mmol mol-1, and two levels of number of air exchanges per hour (NAEH), 0.1 h-1 and2.8 h-1. Explants were obtained from photomixotrophically-micropropagated plantlets. Four explantsper vessel were cultured under cool-white fluorescent lamps for 16 h d-1 at 25 1oC and 70~80% rel-ative humidity. In treatments of 2.8 h-1 NAEH, a 10 mm round hole made on the vessel cap was sealedwith a microporous filter and two CO2 concentrations in the culture rooms were provided from a liq-uefied CO2 tank. Fresh and dry weights, height, length of the longest root, number of leaves, and leafarea significantly increased with increasing PPF and especially, CO2 concentration. Growth wasenhanced by a 2.8 h-1 NAEH. Overall, treatment with a 220mmol m-2 s-1 PPF and a 1000mmol mol-1CO2 resulted in the most vigorous growth of Limonium spp. cean Blueplantlets.

A Study of the Optimal Process Conditions of AZO:H₂ Thin Film for Maximization of the Transmittance of a Blue GaN Light-Emitting Diode with a Wavelength of 470 nm

Hwang, Seung-Taek,Park, Choon-Bae,Hoang, Geun-C. The Korean Institute of Electrical and Electronic 2010 Transactions on Electrical and Electronic Material Vol.11 No.6

This study has been carried out to determine the optimal process conditions of $AZO:H_2$ thin films for the maximization of the transmittance of a blue GaN light-emitting diode (LED) with a wavelength of 470 nm. The Al-doped zinc oxide $(AZO):H_2$ thin films were deposited on a sapphire substrate by radio-frequency magnetron sputtering system with varying substrate temperatures, working pressures and annealing temperatures temperature, working pressure and annealing imposed on a AZO (2wt% $Al_2O_3$) ceramic target. The effect of these variables was investigated in order to improve the light extraction efficiency of the LED. As a result, the (002)-oriented peak was found in all the $AZO:H_2$ thin films. The lowest resistivity and the best transmittance at a wavelength of 470 nm was found to be $4.774\;{\times}\;10^{-4}\;{\Omega}cm$ and 92% at a substrate temperature of $500^{\circ}C$, working pressure of 7 mTorr and annealing temperature of $400^{\circ}C$. The transmittance of the $AZO:H_2$ thin film for the Blue GaN LED was improved by approximately 13% relative to that of a ITO thin film (T = 79%).