Fabrication and optoelectronic properties of novel p-Si/PPy/n-Cu_xIn_1−xO hybrid heterojunction

Mageshwari, K.,Cho, Inje,Park, Jinsub ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.690 No.-

<P><B>Abstract</B></P> <P>In the present work, we report the photoresponse characteristics of the hybrid heterojunction consisting of polypyrrole (PPy) sandwiched between p-Si substrate and n-Cu<SUB>x</SUB>In<SUB>1−x</SUB>O film. Experimental results revealed that the PPy interlayer influence the electronic conduction through the hybrid heterojunction. Structural analysis by X-ray diffraction showed the diffraction peaks corresponding to CuO and In<SUB>2</SUB>O<SUB>3</SUB>, while the optical absorption spectra exhibited strong absorption in both the UV as well as visible regions. Morphological analysis by scanning electron microscopy showed the uniform coverage on the Si substrate, and the effective binding of Cu<SUB>x</SUB>In<SUB>1−x</SUB>O and PPy. Raman spectroscopy showed the vibration modes corresponding to CuO, In<SUB>2</SUB>O<SUB>3</SUB> and PPy. The p-Si/PPy/n-Cu<SUB>x</SUB>In<SUB>1−x</SUB>O hybrid heterojunction demonstrated excellent rectifying behavior and improved electrical characteristics such as high rectification ratio (∼220), lower threshold voltage (∼1.8 V) and ideality factor (∼2.06) due to the PPy insertion and photon illumination. The enhanced electrical characteristics of the hybrid p-Si/PPy/n-Cu<SUB>x</SUB>In<SUB>1−x</SUB>O heterojunction was discussed with respect to the energy band structure, and found that the intermediate PPy layer acting as a hole transporting layer improves the charge selectivity and facilitates the effective transport of charge carriers towards the respective electrodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> p-Si/PPy/n-Cu<SUB>x</SUB>In<SUB>1−x</SUB>O hybrid heterojunction fabricated. </LI> <LI> Polypyrrole (PPy) used as an interfacial buffer layer. </LI> <LI> Hybrid heterojunction exhibit excellent rectifying behavior and enhanced photoresponse. </LI> <LI> Intermediate PPy layer improve charge selectivity and facilitate effective charge transport. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A 2D/2D BiPO4/g-C3N4-B Z-type heterojunction for enhanced photocatalytic degradation of dye pollutants

Zhao Hong-jian,Zhou Yan,Wu Ren-Jang,Han Zheng-bing,Li Xu,Yu Zhe 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.12

A 2D/2D BiPO4/g-C3N4-B nano-sheet heterojunction photocatalyst was synthesized via a simple coprecipitation method at room temperature using glacial acetic acid as solvent, which showed excellent activity toward the degradation of rhodamine B (RhB). The heterojunction showed much higher efficiency of separation and transfer of photogenerated carriers compared to that of its constituents. Moreover, the spectral response range of BiPO4 was effectively broadened after the combination of g-C3N4-B and BiPO4. Consequently, a 97.3% degradation of RhB within 25 min by BiPO4/g-C3N4-B heterojunction photocatalyst under visible light irradiation was observed. The difference in work functions of BiPO4 and g-C3N4-B was evident from UPS characterization, which led to the bending of the energy band and the establishment of an internal electric field at the interface of the heterojunction. Therefore, the synthesized direct Z-type BiPO4/g-C3N4-B heterojunction enhanced the oxidation-reduction ability by promoting the effective separation of photogenerated carriers.

Flexible Multiferroic Bulk Heterojunction with Giant Magnetoelectric Coupling <i>via</i> van der Waals Epitaxy

Amrillah, Tahta,Bitla, Yugandhar,Shin, Kwangwoo,Yang, Tiannan,Hsieh, Ying-Hui,Chiou, Yu-You,Liu, Heng-Jui,Do, Thi Hien,Su, Dong,Chen, Yi-Chun,Jen, Shien-Uang,Chen, Long-Qing,Kim, Kee Hoon,Juang, Jenh- American Chemical Society 2017 ACS NANO Vol.11 No.6

<P>Magnetoelectric nanocomposites have been a topic of intense research due to their profound potential in the applications of electronic devices based on spintronic technology. Nevertheless, in spite of significant progress made in the growth of high-quality nanocomposite thin films, the substrate damping effect still remains a major hurdle in realizing the ultimate magneto electric coupling. To overcome this obstacle, an alternative strategy of fabricating a self-assembled ferroelectric-ferrimagnetic bulk heterojunction on a flexible muscovite via van der Waals epitaxy is adopted. hi this study, we investigated the magnetoelectric coupling in a self-assembled BiFeO3 (BFO)-CoFe2O4 (CFO) bulk heterojunction epitaxially grown on a flexible muscovite substrate. The obtained heterojunction is composed of vertically aligned multiferroic BFO nanopillars embedded in a ferrimagnetic CFO matrix. Moreover, due to the weak interaction between the flexible substrate and bulk heterojunction, the interface is incoherent and, hence, the substrate damping effect is greatly reduced. The phase-field simulation model also complements our results. The magnetic and electrical characterizations highlight the improvement in magnetoelectric coupling of the BFO-CFO bulk heterojunction. A magnetoelectric coupling coefficient of 74 mV/cm.Oe of this bulk heterojunction is larger than the magnetoelectric coefficient reported earlier on flexible substrates. Therefore, this study delivers a viable route of fabricating a remarkable magnetoelectric heterojunction and yet flexible electronic devices that are robust against extreme conditions with optimized performance.</P>

Novel CoAl-LDH/g-C₃N₄/RGO ternary heterojunction with notable 2D/2D/2D configuration for highly efficient visible-light-induced photocatalytic elimination of dye and antibiotic pollutants

Jo, Wan-Kuen,Tonda, Surendar Elsevier 2019 Journal of hazardous materials Vol.368 No.-

<P><B>Abstract</B></P> <P>In this study, we fabricate a novel ternary heterojunction comprising CoAl-layered double hydroxide, g-C<SUB>3</SUB>N<SUB>4</SUB>, and reduced graphene oxide (LDH/CN/RGO) with a notable 2D/2D/2D configuration using a simple one-step hydrothermal method. The visible-light-induced LDH/CN/RGO ternary heterojunctions displayed significantly enhanced photocatalytic performance towards the degradation of aqueous Congo red (CR, dye) and tetracycline (TC, antibiotic) contaminants, which is far superior to that observed for pristine CN (base material), LDH, P25 (reference), and binary CN/RGO and LDH/CN heterojunctions. In particular, the LDH/CN/RGO ternary heterojunction with RGO and LDH contents of 1 wt.% and 15 wt.%, respectively, exhibited the highest degradation activity among all the fabricated catalysts, and it also displayed exceptional stability during recycling experiments. The significant enhancement in the photocatalytic performance and good stability of existing LDH/CN/RGO ternary heterojunctions were primarily attributed to the large intimate interfacial contact between constituent CN, LDH, and RGO prompted by their exceptional 2D/2D/2D arrangement, which accelerates the interfacial charge-transfer processes to effectively hinder the recombination of photoexcited charge carriers. The present study provides new insights into the rational design and fabrication of novel g-C<SUB>3</SUB>N<SUB>4</SUB>-based 2D/2D/2D layered ternary heterojunctions as high-performance photocatalysts, and promotes their application in addressing diverse energy and environmental issues.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CoAl-LDH/g-C<SUB>3</SUB>N<SUB>4</SUB>/RGO 2D/2D/2D ternary heterojunction was fabricated for the first time. </LI> <LI> Ternary heterojunction showed excellent performance for CR and TC photodegradation. </LI> <LI> Greater charge separation owing to large interfacial contact contributed to high activity. </LI> <LI> Ternary heterojunctions displayed high photostability during recycling experiments. </LI> <LI> Possible degradation pathways of CR and TC were proposed based on LC/MS/MS results. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Photoresponse Properties of Reduced Graphene Oxide/n-silicon Heterojunction Fabricated by the Vacuum Filtration and Transfer Method

Yonggang Du,Liangxin Qiao,Dingyuan Xue,Yulei Jia 한국광학회 2022 Current Optics and Photonics Vol.6 No.4

A photodetector based on a reduced graphene oxide (RGO)/n-Si heterojunction with high responsivity, detectivity and fast response speed is presented. Here, we put forward a simple vacuum filtration method to prepare RGO film and transfer it onto an n-Si substrate to form an RGO/n-Si heterojunction. The experimental results show that the heterojunction has good rectification characteristics, and the response and recovery time are less than 0.31 s and 0.25 s, respectively. Under 470 nm light conditions at −2 V applied voltage, the responsivity and detectivity of the device are 65 mA/W and 4.02 × 10 10cmHz 1/2 W −1 , respectively. The simple preparation process and good performance of the RGO/n-Si heterojunction make it a promising material for photoelectric detection, especially in the near-ultraviolet band.

Conformally coated BiVO₄ nanodots on porosity-controlled WO₃ nanorods as highly efficient type II heterojunction photoanodes for water oxidation

Lee, Mi Gyoung,Kim, Do Hong,Sohn, Woonbae,Moon, Cheon Woo,Park, Hoonkee,Lee, Sanghan,Jang, Ho Won Elsevier 2016 Nano energy Vol.28 No.-

<P><B>Abstract</B></P> <P>Bismuth vanadate (BiVO<SUB>4</SUB>) has become a hot topic for solar hydrogen generation by water oxidation due to its appropriate band edges, and narrow band gap. However, the actual conversion efficiency achieved with BiVO<SUB>4</SUB>-based photoanodes is considerably less than the theoretical values because of drawbacks such as poor electron transportation and slow kinetics of oxygen evolution. In these respects, formation of nanostructured heterojunctions is considered to have a marked effect in terms of improving the photoactivities of BiVO<SUB>4</SUB> photoanodes since it is possible to enhance the charge transfer at the interface and increase light absorption significantly. Herein, we report the synthesis and photoelectrochemical (PEC) properties of various BiVO<SUB>4</SUB>-based heterojunction anodes based on stoichiometric BiVO<SUB>4</SUB> by pulsed electrodeposition. We show that WO<SUB>3</SUB> is the optimum bottom layer for a type II band system with BiVO<SUB>4</SUB> among various metal oxides. It is revealed that the photocurrent density of bare WO<SUB>3</SUB> nanorods can be changed drastically by controlling the porosity and aspect ratio and thus BiVO<SUB>4</SUB>/WO<SUB>3</SUB> heterojunction anodes show as similar tendency to bare WO<SUB>3</SUB> nanorods. Under the optimum conditions, a BiVO<SUB>4</SUB>/WO<SUB>3</SUB> heterojunction anode can lead to a high photocurrent density of 4.55mA/cm<SUP>2</SUP> and an incident photon to current conversion efficiency of 80% at 1.23V versus a reversible hydrogen electrode without additional catalyst. Cross-sectional transmission electron microscopy shows that dot-like BiVO<SUB>4</SUB> is well decorated on the entire surface of WO<SUB>3</SUB> nanorods. This systematic study provides a viewpoint on the crucial role of the active area of the bottom layer for high-performance BiVO<SUB>4</SUB>-based type II heterojunction photoanodes, and the proposed concept is applicable to various photoelectrode systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This is the first systematic study between PEC properties and band structures of BiVO<SUB>4</SUB>-based heterojunction. </LI> <LI> Control of active areas of WO<SUB>3</SUB> is the key to achieve high PEC efficiency of BiVO<SUB>4</SUB>/WO<SUB>3.</SUB> </LI> <LI> Conformally coated 3D BiVO<SUB>4</SUB> nanodots on the surface of WO<SUB>3</SUB>-NRs was firstly reported. </LI> <LI> Our BiVO<SUB>4</SUB>/WO<SUB>3</SUB> show the highest photocurrent without catalyst or doping reported to date. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

First-principles study of nitrogen defect g-C3N4/WS2 heterojunction on photocatalytic activity

Wang Yin,Lei Shulai,Zhang Xin,Zhou Shuxing 한국물리학회 2022 Current Applied Physics Vol.39 No.-

In this work, first-principles density functional theory simulations have been performed to investigate the influence of nitrogen (N) defect on the supercell structure, electronic structure and photocatalytic properties of g-C3N4/WS2 heterojunctions. Analyses of calculated binding energies and the lattice mismatch ratios led us to confirm that N-deficient g-C3N4 and WS2 were in parallel contact and form a stable heterojunction. Furthermore, the work functions, molecular dynamics simulations, charge density differences, band structures, DOS, electronic and optical properties and absorption spectra of different g-C3N4/WS2 heterojunctions have been analyzed in detail. It is revealed that the compositing of N-deficient g-C3N4 with WS2 improves the separation of photoinduced electron-hole pairs. N-defect enhances the visible light absorption of the heterojunction, due to the introduction of impurity energy levels. Moreover, the introduction of defect species further improves the photocatalytic performance of g-C3N4/WS2 heterojunction in the visible region.

Integrating magnetized bentonite and pinecone-like BiOBr/BiOI Step-scheme heterojunctions as novel recyclable photocatalyst for efficient antibiotic degradation

Guofu Huang,Kun Liu,Yaseen Muhammad,Tian Fu,Linxing Wang,Jiajing Nong,Shiqi Xu,Luying Jiang,Zhangfa Tong,Hanbing Zhang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.122 No.-

Utilizing the cost-effective natural clay and surface heterojunction engineering to synergistically constructan efficient heterojunction system and promote the separation of photogenerated charges is anappealing strategy for achieving superior photocatalytic activity. In this study, BiOBr/BiOI step-scheme(S-scheme) heterojunction in-suit grown on magnetized bentonite (MBT) was first engineered via facileand mild coprecipitation coupling microwave solvothermal process. The optimized magnetic bentonite/BiOBr/BiOI (MBT25/BiOBr/BiOI, the mass ratio of MBT to BiOBr/BiOI was 25%) attained the largest reactionrate constant (k = 0.021 min1) in tetracycline (TC) photocatalytic degradation within 80 min visible-lightirradiation. In addition, the reaction rate constant k of MBT25/BiOBr/BiOI for TC degradation was 10.51folds higher than that of pristine BiOI. Significantly, the characterization results demonstrated thatMBT effectively assisted the pinecone-like morphology formation of BiOBr/BiOI and endowed the wonderfulmagnetic-separation ability for MBT25/BiOBr/BiOI. Additionally, MBT ingeniously introduced atthe interface could couple with S-scheme heterojunction between BiOBr and BiOI to synergistically boostthe separation and transfer of photogenerated charges. As expected, superior photochemical propertiesand efficient production of active species over MBT25/BiOBr/BiOI were confirmed. Notably, recyclingexperiments verified the wonderful photocatalytic stability and high recovery efficiency of MBT25/BiOBr/BiOI. Furthermore, the abundant O2and OH active species led to hydroxylation, dealkylation,deamidation and ring opening of TC molecules. A synergistically enhanced mechanism over S-schemeMBT25/BiOBr/BiOI was clarified based on band structure calculations. This study offers an innovative perspectiveto design multifunctional photocatalysts with superior activity by integrating properties of magnetizedclay and S-scheme heterojunction.

Construction of Bi₂WO₆/RGO/g-C₃N₄ 2D/2D/2D hybrid Z-scheme heterojunctions with large interfacial contact area for efficient charge separation and high-performance photoreduction of CO₂ and H<sub>2</

Jo, Wan-Kuen,Kumar, Santosh,Eslava, Salvador,Tonda, Surendar Elsevier 2018 Applied Catalysis B Vol.239 No.-

<P><B>Abstract</B></P> <P>We have rationally constructed a hybrid heterojunction comprising of Bi<SUB>2</SUB>WO<SUB>6</SUB>, reduced graphene oxide, and g-C<SUB>3</SUB>N<SUB>4</SUB> (BWO/RGO/CN) with a 2D/2D/2D configuration for efficient photoreduction to generate solar fuels. These heterojunctions displayed dramatically improved performance towards CO<SUB>2</SUB> reduction to generate CO and CH<SUB>4</SUB> under visible-light irradiation, compared to the base material (CN), P25 as reference, as well as binary BWO/CN and RGO/CN heterojunctions. Particularly, the BWO/RGO/CN heterojunctions with 1 wt. % RGO and 15 wt. % BWO achieved record performance in the yields of carbonaceous products (CO + CH<SUB>4</SUB>) compared to other synthesized catalysts, with a selectivity of 92% against H<SUB>2</SUB>. The remarkable photocatalytic performance was mainly attributed to the unique 2D/2D/2D architecture that creates large interfacial contact between the constituent materials for rapid charge transfer, to hinder the direct recombination of photoinduced electrons and holes. Notably, RGO played two significant roles: as a supporter to capture the electrons from CN, and as a redox mediator to promote the Z-scheme charge transfer between CN and BWO. The result is a greater extent of charge separation in the present BWO/RGO/CN heterojunction system, as evidenced by the photoluminescence, photocurrent responses, and electron microscopy findings. More importantly, the heterojunctions displayed excellent stability during recycling tests with no obvious loss in the generation of CO and CH<SUB>4</SUB> from photoreduction of CO<SUB>2</SUB>. This interesting interfacial engineering approach presented herein offers a promising route for the rational design of a new class of layered multicomponent heterojunctions with 2D/2D/2D architecture for various applications in environmental protection and solar energy conversion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bi<SUB>2</SUB>WO<SUB>6</SUB>/RGO/g-C<SUB>3</SUB>N<SUB>4</SUB> hybrid heterojunctions with 2D/2D/2D configuration were fabricated. </LI> <LI> Heterojunctions showed excellent CO<SUB>2</SUB> photoreduction activity to generate solar fuels. </LI> <LI> RGO plays dual roles as a supporter and a redox mediator to promote charge separation. </LI> <LI> Rapid charge transfer due to large interfacial contact contributed to high activity. </LI> <LI> Hybrid heterojunctions exhibited high photostability during recycling experiments. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microwave-assisted rapid synthesis of Cu2S:ZnIn2S4 marigold-like nanoflower heterojunctions and enhanced visible light photocatalytic hydrogen production via Pt sensitization

마하데오,루틴,채원식,Hyun Hwi Lee,Min Cho,Jum Suk Jang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

In this work, a rapid microwave synthesis route is presented for the fabrication of morphology-controlledCu2S: ZnIn2S4 marigold-like nanoflower heterojunction photocatalysts. The Cu-to-Zn-metal -cation (Cu:Zn) ratios were used to control the Cu2S: ZnIn2S4 heterojunction during the second step of microwavesynthesis. The formation of Cu2S: ZnIn2S4 heterojunction is evidenced by XRD, TEM and XPS analyses. The optimum electronic interaction aids to stimulate electron-hole charge separation kinetics and promotethe solar hydrogen (H2) evolution performance in microwave-assisted 5 mol.% Cu2S:ZnIn2S4(Cu2S:ZIS–5) heterojunction. Benefiting from the synergy between marigold-like morphology, heterojunction,and Pt loading, the optimum Pt loaded Cu2S: ZIS–5 marigold nanoflowers (Pt/Cu2S:ZIS–5) exhibitedthe 862 mmol of photocatalytic H2 production after 3 h under visible light irradiation (420 nm). Thetime-resolved PL spectrum showed more than double carrier lifetime in Pt/Cu2S: ZIS–5 heterojunction(45 ns) than that of Pt/ZIS–15 (20 ns). These visible light-responsive Pt/Cu2S:ZIS marigold-like nanoflowerheterojunction shows promising photostability, which would open new opportunities for the developmentof highly efficient ternary metal-chalcogenide photocatalysts for solar hydrogen generation.