In situ construction of protonated g-C3N4/Ti3C2 MXene Schottky heterojunctions for efficient photocatalytic hydrogen production

Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to realize carbon-free hydrogen production remains a challenge.Heterojunction photocatalysts with well-defined dimensionality and perfectly matched interfaces are promising for achieving highly efficient solar-to-hydrogen conversion.Herein,we report the fabrication of a novel type of protonated graphitic carbon nitride(PCN)/Ti3C2 MXene heterojunctions with strong interfacial interactions.As expected,the two-dimensional(2D)PCN/2D Ti3C2 MXene interface heterojunction achieves a highly improved hydrogen evolution rate(2181μmol∙g‒1)in comparison with bulk g-C3N4(393μmol∙g‒1)and protonated g-C3N4(816μmol∙g‒1).The charge-regulated surfaces of PCN and the accelerated charge transport at the face-to-face 2D/2D Schottky heterojunction interface are the major contributors to the excellent hydrogen evolution performance of the composite photocatalyst.

Efficient photocatalytic hydrogen evolution coupled with benzaldehyde production over 0D Cd_(0.5)Zn_(0.5)S/2D Ti_(3)C2 Schottky heterojunction

Converting water into hydrogen fuel and oxidizing benzyl alcohol to benzaldehyde simultaneously under visible light illumination is of great significance,but the fast recombination of photogenerated carriers in photocatalysts seriously decreases the conversion efficiency.Herein,a novel dual-functional 0D Cd_(0.5)Zn_(0.5)S/2D Ti_(3)C2 hybrid was fabricated by a solvothermally in-situ generated assembling method.The Cd_(0.5)Zn_(0.5)S nano-spheres with a fluffy surface completely and uniformly covered the ultrathin Ti_(3)C2 nanosheets,leading to the increased Schottky barrier(SB)sites due to a large contact area,which could accelerate the electron–hole separation and improve the light utilization.The optimized Cd_(0.5)Zn_(0.5)S/Ti_(3)C2 hybrid simultaneously presents a hydrogen evolution rate of 5.3 mmol/(g·h)and a benzaldehyde production rate of 29.3 mmol/(g·h),which are~3.2 and 2 times higher than those of pristine Cd_(0.5)Zn_(0.5)S,respectively.Both the multiple experimental measurements and the density functional theory(DFT)calculations further demonstrate the tight connection between Cd_(0.5)Zn_(0.5)S and Ti_(3)C2,formation of Schottky junction,and efficient photogenerated electron–hole separation.This paper suggests a dual-functional composite catalyst for photocatalytic hydrogen evolution and benzaldehyde production,and provides a new strategy for preventing the photogenerated electrons and holes from recombining by constructing a 0D/2D heterojunction with increased SB sites.

High-gain signal-on PEDOT:PSS organic photoelectrochemical transistor biosensing modulated by a MXene/MOFs/NiO Schottky heterojunction

Herein we report a high-gain signal-on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)organic electrochemical transistor(OECT)biosensing using an accumulation-mode PEDOT:PSS OECT modulated by a light-fueled MXene/MOFs/Ni O Schottky heterojunction.In such a system,the MXene/MOFs/Ni O Schottky heterojunction exhibited superior gating effect,as it not only enabled the fast-directional charge transfer but also guaranteed the maximal accessibility of the electrolyte to topped 2D MXene with large surface area.In linkage with a bi-enzyme cascade system,the quinone derivatives produced by the cascade reaction of alkaline phosphatase(ALP)and tyrosinase(TYR)could serve as effective electron acceptors for the representative Ti_(3)C_(2)/PCN-224/Ni O heterojunction,underpinning an innovative method for sensitive detection of ALP activity with a low detection limit of 0.001 U L^(-1).Remarkably,the as-developed system demonstrated a remarkable current gain as high as near 10^(4),which to our knowledge is the highest one among existing OECT biosensory devices.This work represents a generic protocol to develop the novel signal-on PEDOT:PSS OECT platform towards biochemical detection and beyond.

2D/2D Ti_(3)C_(2) MXene/HTiNbO_(5) nanosheets Schottky heterojunction for boosting photothermal-assisted solar-driven photodegradation of tetracycline hydrochloride

Developing high-efficiency photocatalysts for tetracycline hydrochloride(TCH)degradation is of great sig-nificance to ecosystems and human beings.In this work,a two-step process of exfoliation and re-stacking was performed to prepare re-stacked HTiNbO_(5) nanosheets(R-HTNS)and then coupled with Ti_(3)C_(2) MXene to construct Ti_(3)C_(2) MXene/R-HTNS(MX/RTS)with a 2D/2D Schottky heterojunction.These 2D/2D het-erostructures between Ti_(3)C_(2) MXene and R-HTNS can produce an internal electric field and provide max-imum interface area for efficient charge transfer across the intimate interface.The photocatalytic perfor-mance of samples was evaluated by TCH degradation under simulated sunlight.The MX/RTS composites,with an optimal sample of 3-MX/RTS,show enhanced photocatalytic activity for TCH degradation com-pared with R-HTNS.The characterization results reveal that the introduction of Ti_(3)C_(2) MXene can signif-icantly increase specific surface area for providing more reactive sites and broaden the light absorption region.Besides,the incident light energy is absorbed by the Ti_(3)C_(2) MXene component in MX/RTS compos-ites to generate photothermal energy(heat),which facilitates the charge carrier separation and surface reaction kinetics.Thus,the enhanced TCH photodegradation activity for MX/RTS composites is due to the introduction of Ti_(3)C_(2) MXene,which possesses the synergistic effect of the increased specific surface area,improved light-harvesting capacity,2D/2D Schottky heterojunction,and photothermal energy effect.Additionally,the TCH photodegradation behavior is deliberated with a detailed discussion on various co-existing ions.During TCH photodegradation,the active radical species are determined for 3-MX/RTS.Ac-cording to the characterization results,the possible TCH photodegradation pathway and mechanism over 3-MX/RTS are explored.This work may offer a novel insight for constructing MXene-based heterostruc-tured photocatalysts with high efficiency.

Boosting photocatalytic hydrogen evolution of g-C_(3)N_(4) catalyst via lowering the Fermi level of co-catalyst

The photocatalytic performances are highly dependent on the charge separation and surface reaction kinetics of photocatalysts.Aiming at figuring out the effects of co-catalyst with the lower Fermi level on photocatalytic activity,we tuned the Fermi level of Pt nanoparticles on g-C_(3)N_(4)(GCN)by introducing Co atom.Experimental results show that lowering the Fermi level of co-catalyst does not alter light absorption of GCN due to the invariable structure.Besides,Pt_(3)Co with a lower Fermi level contributes less positive influence on charge separation in GCN due to an opposite effect from the stronger electron-trap ability of Pt_(3)Co and increased band bending in GCN-Pt_(3)Co.The density functional theory(DFT)calculations indicate that GCN-Pt_(3)Co has faster surface reaction kinetics than GCN-Pt,owing to easier dissociation of H_(2)O molecules and faster desorption of H^(*)on Pt_(3)Co.Consequently,GCN-Pt_(3)Co exhibits an excellent H_(2) evolution rate with 2.91 mmol g^(-1)·h^(-1),which 2.67 times that of GCN-Pt.

基于极性可重构WSe_(2)肖特基异质结的非对称逻辑整流器和光电探测器

基于二维材料范德华异质结的自驱动光电探测器是逻辑光电子器件和智能图像传感器的重要组成部分.本文通过机械剥离和干法转移制备了一种底部Au接触的PtSe_(2)/WSe_(2)/Au非对称肖特基光电二极管.栅极可调的Au/WSe_(2)肖特基势垒大小、弱费米钉扎效应、高半金属PtSe_(2)导电率以及良好的PtSe_(2)/WSe_(2)层间耦合效应使得该二极管产生极性可重构现象,可实现栅极可调正负整流行为,且整流比变化范围在10−2到104之间,达到6个量级.我们利用此特性验证了半波逻辑整流器功能.此外,此自驱动器件的最大光响应度达316 mA W^(−1),最大光开关比达105,光电转换效率为4.62%,响应时间仅为830/950μs.光电流微区扫描结果表明,器件的光电流主要分布在Au/WSe_(2)界面边缘,证实该器件为非对称肖特基光电二极管.该器件还实现了高分辨率的可见光单点成像.上述研究结果表明,本工作为制备高性能半波整流器、超快自驱动光电探测器和高分辨图像传感器提供了一种简便有效的策略.

Rapid Ferroelectric‑Photoexcited Bacteria‑Killing of Bi_(4)Ti_(3)O_(12)/Ti_(3)C_(2)T_(x) Nanofiber Membranes

In this study,an antibacterial nanofiber membrane[polyvinylidene fluoride/Bi_(4)Ti_(3)O_(12)/Ti_(3)C_(2)T_(x)(PVDF/BTO/Ti_(3)C_(2)T_(x))]is fabricated using an electrostatic spinning process,in which the self-assembled BTO/Ti_(3)C_(2)T_(x) heterojunction is incorporated into the PVDF matrix.Benefiting from the internal electric field induced by the spontaneously ferroelectric polarization of BTO,the photoexcited electrons and holes are driven to move in the opposite direction inside BTO,and the electrons are transferred to Ti_(3)C_(2)T_(x) across the Schottky interface.Thus,directed charge separation and transfer are realized through the cooperation of the two components.The recombination of electron–hole pairs is maximumly inhibited,which notably improves the yield of reactive oxygen species by enhancing photocatalytic activity.Furthermore,the nanofiber membrane with an optimal doping ratio exhibits outstanding visible light absorption and photothermal conversion performance.Ulti-mately,photothermal effect and ferroelectric polarization enhanced photocatalysis endow the nanofiber membrane with the ability to kill 99.61%±0.28%Staphylococcus aureus and 99.71%±0.16%Escherichia coli under 20 min of light irradiation.This study brings new insights into the design of intelligent antibacterial textiles through a ferroelectric polarization strategy.