Versatile role of 2D Ti3C2 MXenes for advancements in the photodetector performance: A review

Adem Sreedhar,Qui Thanh Hoai Ta,Jin-Seo Noh 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.127 No.-

Nowadays, layer-structured two-dimensional (2D) Ti3C2 MXenes have been created a platform as promisingcandidates for developing next-generation photodetectors. Scalable spatial organization of Ti3C2MXenes enables responsive template at the interface of various semiconductors for significant improvementin the photodetector performance. In this review, we provide prospective discussion on geometricalpotentiality of 2D Ti3C2 MXenes to advance the current photodetector device performance. Specifically,we guide the versatility of Ti3C2 MXenes such as a metal electrode, flexible material, transparent nature,and self-power behavior during UV, visible, and broadband photodetector performance. By the excellenceof 2D Ti3C2, we begin to comprehend the Schottky barrier, built-in electric field, and van der Walls heterojunctionformation. It is imperative to understand the vast opportunities of Ti3C2 MXene-based photodetectorseven under flexible conditions, which is higher than conventional gold and graphene. Owing tothe desirable properties, Ti3C2 garnered significant progress in (i) large-size flexible photodetector formationwithout altering the structural and charge carrier properties, (ii) replacing conventional metal electrodesby electrically conductive Ti3C2 in Ti3C2-semiconductor-Ti3C2 (MX-S-MX) photodetector, and (iii)Schottky junction formation at the interface of various semiconductors. Finally, we conclude the status of2D Ti3C2 MXene applicability, challenges, and possible viewpoints for advancement in next-generationphotodetectors.

Insight into anions and cations effect on charge carrier generation and transportation of flake-like Co-doped ZnO thin films for stable PEC water splitting activity

Sreedhar, Adem,Reddy, I. Neelakanta,Hoai Ta, Qui Thanh,Cho, Eunbin,Noh, Jin-Seo Elsevier 2019 Journal of Electroanalytical Chemistry Vol.855 No.-

<P><B>Abstract</B></P> <P>Developing a stable interface interaction between photoelectrode and electrolyte is crucial for achieving superior photoelectrochemical (PEC) water splitting activity. In this aspect, the contribution of anions and cations present in the electrolyte play a decisive role during its interaction with the solvent and surface functional groups on the developed photoelectrode, which greatly determine the charge carrier generation and transportation. Herein, we developed the flake-like Co (1.7 at.%)-doped ZnO (Co-ZnO) thin films by employing simultaneous RF and DC magnetron sputtering, which were post annealed at 250 °C for 2 h. The developed films were used to demonstrate the PEC activity under different aqueous electrolytes (KCl, KOH, NaOH, Na<SUB>2</SUB>SO<SUB>3</SUB> and Na<SUB>2</SUB>SO<SUB>4</SUB>). Most importantly, owing to the promising flake-like features of Co-ZnO, efficient electrode-electrolyte interface interaction has been achieved for stable and improved PEC activity. In turn, detailed PEC activity in KCl, KOH and NaOH electrolytes demonstrated that K<SUP>+</SUP> cations and OH<SUP>−</SUP> anions in KOH greatly influenced the photocurrents than KCl (Cl<SUP>−</SUP>) and NaOH (Na<SUP>+</SUP>) due to the high ionic conductive and diffusion properties. On the other hand, SO<SUB>3</SUB> <SUP>2−</SUP> (Na<SUB>2</SUB>SO<SUB>3</SUB>) anions tailor the charge carrier generation by the advantage of hole scavenging activity compared to SO<SUB>4</SUB> <SUP>2−</SUP> (Na<SUB>2</SUB>SO<SUB>4</SUB>). Comprehensively, our results provide new insight into the selection of aqueous electrolyte to improve the PEC water splitting activity through adopting the ionic conductivity and constructive interaction with photoelectrode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flake-like Co (1.7 at.%)-doped ZnO thin films were deposited by RF and DC sputtering. </LI> <LI> Surface interface interaction between Co-ZnO and aqueous electrolytes was explored. </LI> <LI> Ion conductive and diffusion properties highlighted stable and superior PEC activity. </LI> <LI> Photocurrents in KOH (2.3 × 10<SUP>−6</SUP> A/cm<SUP>2</SUP>) > NaOH (2.0 × 10<SUP>−6</SUP> A/cm<SUP>2</SUP>) > KCl (8.7 × 10<SUP>−7</SUP> A/cm<SUP>2</SUP>). </LI> <LI> Na<SUB>2</SUB>SO<SUB>3</SUB> acts as a hole scavenger for superior PEC activity than Na<SUB>2</SUB>SO<SUB>4</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>This study comprehensively explores the anions and cations effect on charge carrier generation and transportation of flake-like Co (1.7 at.%)-doped ZnO thin films for stable PEC water splitting activity under various aqueous electrolytes.</P> <P>[DISPLAY OMISSION]</P>

Plasmonic Ag nanowires sensitized ZnO flake-like structures as a potential photoanode material for enhanced visible light water splitting activity

Sreedhar, Adem,Neelakanta Reddy, I.,Ta, Qui Thanh Hoai,Namgung, Gitae,Noh, Jin-Seo Elsevier 2019 Journal of Electroanalytical Chemistry Vol.832 No.-

<P><B>Abstract</B></P> <P>Silver nanowires (AgNWs) functionalized ZnO flake-like (ZnO/AgNWs) morphological heterostructures were developed as a promising photoanode by facile RF magnetron sputtering and polyol methods. Herein, we demonstrate the role of rationally tailored AgNWs weight concentration (0, 0.03, 0.05 and 0.07g) on ZnO flake-like morphology for enhanced visible-light-driven photoelectrochemical (PEC) water splitting activity. From XRD studies, ZnO (002) facets were effectively influenced by the selective growth of Ag (111) facets. Notably, XPS studies reveal the strong correlation between AgNWs and ZnO, showing a significant red shift in Zn 2p and O 1s levels and blue shift in Ag 3d level. Whereas, surface hydroxyl groups (OH<SUP>−</SUP>) were originated on ZnO/AgNWs heterostructure, which acts as light trapping states. Interestingly, FESEM images comprise AgNWs distribution on ZnO flake-like morphology, which suggests AgNWs are most accessible networks at the interface of ZnO. As a result, we observed significant variation in the optical transmittance and matching band gap for strong visible light absorption. In conclusion, selective growth of AgNWs-0.05g on ZnO promoted the strong interface reaction kinetics with impressive photoconversion efficiency (0.38%). Thus, developing of unique flake-like/nanowire morphological features underlined to be crucial interest in energy conversion applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Well-defined AgNWs based ZnO flake-like photoanodes reported for the first time. </LI> <LI> Surface interaction between AgNWs and ZnO serves as a key factor for PEC activity. </LI> <LI> Specific surface area of AgNWs achieved for superior visible light harvesting. </LI> <LI> ZnO/AgNWs (0.05g) photoanodes yielded 0.38% photoconversion efficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Advancements in the photocatalytic activity of various bismuth-based semiconductor/Ti3C2 MXene interfaces for sustainable environmental management: A review

ADEM SREEDHAR,Qui Thanh Hoai Ta,노진서 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Rapidly increasing world population and industrialization are difficult to balance our environment. Monitoring water pollution, depletion of fossil fuels, and greenhouse gas emissions is paramount forthe safety of our ecological system. This review is intended to address the environmental monitoringapplications (toxic matter degradation, H2 evolution, CO2 reduction, and N2 reduction) through the possibleinterfacial insights involved between various bismuth (Bi) based semiconductors and 2D Ti3C2MXenes. In this spotlight, we explored strategic point contact (0D/2D) and face contact (2D/2D) interfaceinformation towards superior charge carrier generation, separation, and shortened charge transfer pathunder suppressed recombination. Considering the diverse morphological advancements in Ti3C2 (multilayer,monolayer, QDs, and completely derived C-TiO2), unique interfacial charge transport mechanismswere revealed. Band alignment modulations distinguishably functionalized the charge carrier separationand its participation in photocatalytic activity. With the control on face contact 2D/2D interface, abundantsurface-active sites promoted toxic dye degradation, CO2, and N2 reduction. Overall, this reviewdescribed the concept of advancements in surface interfacial interaction. Finally, challenges and perspectiveson future research are also provided.

Multifunctional monoclinic VO₂ nanorod thin films for enhanced energy applications: Photoelectrochemical water splitting and supercapacitor

Reddy, I. Neelakanta,Sreedhar, Adem,Shim, Jaesool,Gwag, Jin Seog Elsevier 2019 Journal of Electroanalytical Chemistry Vol.835 No.-

<P><B>Abstract</B></P> <P>Monoclinic VO<SUB>2</SUB> nanorod thin films were deposited on indium‑tin-oxide-coated glass substrates using radio-frequency reactive magnetron sputtering at a substrate temperature of 300°C and various O<SUB>2</SUB> flow rates. The thin films were characterized via standard analysis techniques. The VO<SUB>2</SUB> thin films exhibited a highly crystalline monoclinic phase with an indirect band gap of ~1.73eV. At optimized O<SUB>2</SUB> flow rate (4sccm), the thin films was observed nanorod structures, exhibited a remarkable photocurrent of ~0.08mAcm<SUP>−2</SUP> during photoelectrochemical water splitting in the visible region. Electrochemical performance tests of the nanorod films revealed a specific capacitance of ~486mFcm<SUP>−2</SUP> at a scan rate of 10mVs<SUP>−1</SUP>. In addition, amperometric <I>I</I>–<I>t</I> curves showed that VO<SUB>2</SUB> thin film electrodes were highly stable during the photo-oxidation process. The nanorod films also exhibited a good specific capacitance of ~120mFcm<SUP>−2</SUP> after 5000cycles at a scan rate of 100mVs<SUP>−1</SUP>. The photocurrents during photoelectrochemical water splitting and the specific capacitance of VO<SUB>2</SUB> thin films deposited at O<SUB>2</SUB> flow rates of 2 and 6sccm were 0.06 and 0.07mAcm<SUP>−2</SUP> and 398 and 37mFcm<SUP>−2</SUP>, respectively. The films deposited under Ar at 8sccm and O<SUB>2</SUB> at 4sccm showed the highest photoelectrochemical water splitting performance and specific capacitance, owing mainly to their nanorod-like morphology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> VO<SUB>2</SUB> nanorod thin films were deposited on glass substrates using magnetron sputtering </LI> <LI> A remarkable photocurrent of ~0.08mAcm<SUP>−2</SUP> during water splitting in the visible region </LI> <LI> The VO<SUB>2</SUB> nanorod films has highest specific capacitance of ~486mFcm<SUP>−2</SUP> </LI> <LI> VO<SUB>2</SUB> nanorod obtained at 4sccm of O<SUB>2</SUB> has the highest water splitting and specific capacitance </LI> </UL> </P>

High performance hierarchical SiCN nanowires for efficient photocatalytic - photoelectrocatalytic and supercapacitor applications

Reddy, I. Neelakanta,Sreedhar, Adem,Reddy, Ch. Venkata,Shim, Jaesool,Cho, Migyung,Yoo, Kisoo,Kim, Dongseob,Gwag, Jin Seog Elsevier 2018 Applied Catalysis B Vol.237 No.-

<P><B>Abstract</B></P> <P>We synthesized SiCN nanowires by a combination of high-energy ball milling and post-heat treatment using high-purity silicon and carbon nanopowders (<100 nm), and evaluated the effects of process parameters on their structural, chemical, optical properties, photoelectrocatalytic and photocatalytic activities. Cubic SiCN crystal phase with a lattice constant of 4.35 Å was observed. The optical bandgap of 2.20 eV was observed with nanowire diameters ranging from 23 nm to 37 nm. The SiCN nanowires showed good photocatalytic activity with the highest degradation percentage of ∼99% in 40 min for the degradation of Rhodamine B dye under visible light, and a degradation rate of 0.0841 min<SUP>−1</SUP>. The SiCN nanowires showed no significant reduction in photocatalytic activity for five consecutive cycles, indicating that they are extremely stable against organic dyes. The SiCN nanowires were used for photoelectrochemical water splitting and the effect of electrolytes was studied. The highest photocurrent density of 5 × 10<SUP>-2</SUP> mAcm<SUP>-2</SUP> vs. Ag/AgCl in 0.1 M KOH solution was achieved owing to the improved visible light collection and electron hole separation. The exchange current density, Tafel slopes, and limiting diffusion current density were found to be 3.17 mAcm<SUP>-2</SUP>, 68.13 mVdec<SUP>−1</SUP>, and 1.54 mAcm<SUP>-2</SUP>, respectively. Further, the specific capacitance of the SiCN nanowires was estimated, obtained of 188 mFcm<SUP>-2</SUP> at a current density of 5 mAcm<SUP>-2</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel hierarchical SiCN photocatalyst has been prepared via the combination of ball milling and heat treatment techniques. </LI> <LI> The SiCN nanowires show an RhB degradation of ∼99% in 40 min under visible light illumination. </LI> <LI> The photocatalyst exhibits an extremely high photocurrent current and long-term photostability, strongly depended on the type of electrolyte. </LI> <LI> 188 mFcm<SUP>−2</SUP> specific capacitance of the SiCN nanowires was achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced visible-light photocatalytic performance of Fe3O4 nanopyramids for water splitting and dye degradation

Reddy, I. Neelakanta,Sreedhar, Adem,Reddy, Ch. Venkata,Shim, Jaesool,Cho, Migyung,Kim, Dongseob,Gwag, Jin Seog,Yoo, Kisoo Springer-Verlag 2018 Journal of solid state electrochemistry Vol.22 No.11

Systematic studies of Bi₂O₃ hierarchical nanostructural and plasmonic effect on photoelectrochemical activity under visible light irradiation

Reddy, I. Neelakanta,Reddy, Ch. Venkata,Sreedhar, Adem,Cho, Migyung,Kim, Dongseob,Shim, Jaesool Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.14

<P><B>Abstract</B></P> <P>The effect of Ag plasmonic nanowire layers on the hierarchical nanostructure of Bi<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes for water splitting under visible light irradiation was studied for the first time. In addition, the impact of various Bi<SUB>2</SUB>O<SUB>3</SUB> nanostructures on light harvesting and generation of relative photocurrent have been investigated. The cubic structure of Bi<SUB>2</SUB>O<SUB>3</SUB> was confirmed using X-ray diffraction analysis. Optical bandgaps of 2.14 and 2.30 eV have been achieved for the Bi<SUB>2</SUB>O<SUB>3</SUB> nanoparticles and nanoflowers photoelectrodes (BP and BF), respectively. The photocurrent density (J) of the BP featuring Ag plasmonic layer photoelectrode (Ag/BP) was 6.47 mA cm<SUP>−2</SUP>, and was higher than that of the BF featuring Ag plasmonic layer photoelectrode (Ag/BF), which was 4.33 mA cm<SUP>−2</SUP>. These values were approximately 647 and 2165 times higher than those of BP and BF, respectively. However, the J value of BP was 2.13 mA cm<SUP>−2</SUP> higher than that of BF. The superior J values of Ag/BP and Ag/BF were attributed to the increased light absorption and reduced electron-hole recombination rate at the time scale beyond a few 10<SUP>−12</SUP> s, owing to the Ag nanowires. In addition, the plasmonic field was able to reduce the charge recombination rate of the nanostructured electrodes in reactor cells.</P>

Effect of plasmonic Ag nanowires on the photocatalytic activity of Cu doped Fe₂O₃ nanostructures photoanodes for superior photoelectrochemical water splitting applications

Reddy, I. Neelakanta,Reddy, Ch. Venkata,Sreedhar, Adem,Cho, Migyung,Kim, Dongseob,Shim, Jaesool Elsevier 2019 Journal of electroanalytical chemistry Vol.842 No.-

<P><B>Abstract</B></P> <P>The Present study focuses on the synthesis and analysis of Cu doped hematite (α-Fe<SUB>2</SUB>O<SUB>3</SUB>) nanostructures for effectively enhancing the optical properties as well as their implementation as photoelectrodes for energy-harvesting applications. In addition to this, the influence of noble metal plasmonic layer of Ag nanowires as a bottom layer for undoped and doped Fe<SUB>2</SUB>O<SUB>3</SUB> photoanodes has been investigated. Herein, we studied the influence of dopant on morphology, structural, and optical properties of Fe<SUB>2</SUB>O<SUB>3</SUB>. X-ray diffraction technique and X-ray photoelectron spectroscopy analysis were confirmed Cu ion substitution into host Fe<SUB>2</SUB>O<SUB>3</SUB> nanostructures. The optical band gap decreases from ~ 1.95eV to ~ 1.38eV with increasing of Cu dopant concentration. Impedance analysis reveals that the Cu dopant works as an electron donor and improves the Fe<SUB>2</SUB>O<SUB>3</SUB> charge carrier density. The photoelectrochemical water splitting studies reveals that the photoanodes without plasmonic layer was shown improved photocurrents compare to the undoped sample, thus improving the absorption of the incident light. Significantly, the optimized 0.2mol% Cu-doped α-Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes without Ag layer reached the maximum photocurrent density of ~0.31mA/cm<SUP>2</SUP>, ~ 28-fold that of pure Fe<SUB>2</SUB>O<SUB>3</SUB> (0.011mA/cm<SUP>2</SUP>). Further, the same photoanode with plasmonic Ag nanowires showed a significantly improved photocurrent density of 1.48mA/cm<SUP>2</SUP>, which is ~ 135-fold that of pure Fe<SUB>2</SUB>O<SUB>3</SUB> and ~ 5-folds that of 0.2mol% Cu doped α-Fe<SUB>2</SUB>O<SUB>3</SUB> photoelectrodes without plasmonic nanowire layer. The superior photocurrent is ascribed to the enhanced electron donor density and reduced charge recombination rate, as an outcome of optimized Cu doping and Ag nanowires.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu-doped Fe<SUB>2</SUB>O<SUB>3</SUB> and Ag plasmonic nanostructures were synthesized by hydrothermal and polyol methods. </LI> <LI> Optimal 0.2mol% Cu doped Fe<SUB>2</SUB>O<SUB>3</SUB> photoanode showed the highest photocurrent density of 1.48mA/cm<SUP>2</SUP>. </LI> <LI> Photoanode with Ag plasmonic increases the photocurrents of 135-fold that of pure Fe<SUB>2</SUB>O<SUB>3</SUB>. </LI> <LI> Excellent photoelectrochemical water splitting activity was achieved. </LI> </UL> </P>

Structural, optical, and bifunctional applications: Supercapacitor and photoelectrochemical water splitting of Ni-doped ZnO nanostructures

Neelakanta Reddy, I.,Venkata Reddy, Ch.,Sreedhar, Adem,Shim, Jaesool,Cho, Migyung,Yoo, Kisoo,Kim, Dongseob Elsevier 2018 Journal of Electroanalytical Chemistry Vol.828 No.-

<P><B>Abstract</B></P> <P>Over the past few decades, doped ZnO structures have attracted significant attention because of their distinctive properties and a wide range of applications in catalysis and energy-storage devices. However, effective simple synthesis of doped ZnO structures for photoelectrocatalytic and supercapacitor applications still remains challenging. In this study, Ni-doped ZnO structures were synthesized at different Ni concentrations. Analysis of the obtained samples confirmed the formation of Ni-doped ZnO; 1.5 mol% Ni-doped ZnO showed enhanced water splitting activity and supercapacitor properties. The highest photocurrent density of 4.6 mA/cm<SUP>2</SUP> was obtained in a 0.1 M KOH solution at an applied bias photon-to-current efficiency of 4.2%, which is almost twice that obtained with pristine ZnO (2.8%), indicating an enhanced electron-hole separation. Doped ZnO exhibits a photocurrent 1.78 times higher than pristine ZnO under light illumination. Ni-doping induces effective charge separation and transfer, efficiently diminishing the recombination rate and reducing intrinsic defects. Further, the highest specific capacity of ~96 F g<SUP>−1</SUP> was observed for 1.5% Ni-doped ZnO at an applied scan rate of 10 mV s<SUP>−1</SUP>. The optimized sample, 1.5% Ni-doped ZnO, exhibited a high specific capacitance retention and coulombic efficiency of ~98% and ~99.2%, respectively. These results are expected to be very helpful in developing cheap and simple fabrication methods and efficient electrode materials for photoelectrochemical water splitting and supercapacitor applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photoelectrochemical and supercapacitor properties of Ni-doped ZnO has been systematically investigated. </LI> <LI> The 1.5 mol% Ni-doped ZnO showed the highest photocurrent density of 4.6 mA/cm<SUP>2</SUP>. </LI> <LI> The highest specific capacitance of 1.5 mol% Ni-doped ZnO was obtained of ~ 96Fg<SUP>−1</SUP> at 10mVs<SUP>-1</SUP>. </LI> <LI> The optimal 1.5 % Ni-doped ZnO shows the highest specific capacitance retention and Coulombic efficiency of ~98 % and ~99.2 %, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>