Highly Active Interfacial Sites in SFT-SnO_(2) Heterojunction Electrolyte for Enhanced Fuel Cell Performance via Engineered Energy Bands:Envisioned Theoretically and Experimentally

Extending the ionic conductivity is the pre-requisite of electrolytes in fuel cell technology for high-electrochemical performance.In this regard,the introduction of semiconductor-oxide materials and the approach of heterostructure formation by modulating energy bands to enhance ionic conduction acting as an electrolyte in fuel cell-device.Semiconductor(n-type;SnO_(2))plays a key role by introducing into p-type SrFe_(0.2)Ti_(0.8)O_(3-δ)(SFT)semiconductor perovskite materials to construct p-n heterojunction for high ionic conductivity.Therefore,two different composites of SFT and SnO_(2)are constructed by gluing p-and n-type SFT-SnO_(2),where the optimal composition of SFT-SnO_(2)(6∶4)heterostructure electrolyte-based fuel cell achieved excellent ionic conductivity 0.24 S cm^(-1)with power-output of 1004 mW cm^(-2)and high OCV 1.12 V at a low operational temperature of 500℃.The high power-output and significant ionic conductivity with durable operation of 54 h are accredited to SFT-SnO_(2)heterojunction formation including interfacial conduction assisted by a built-in electric field in fuel cell device.Moreover,the fuel conversion efficiency and considerable Faradaic efficiency reveal the compatibility of SFT-SnO_(2)heterostructure electrolyte and ruled-out short-circuiting issue.Further,the first principle calculation provides sufficient information on structure optimization and energy-band structure modulation of SFT-SnO_(2).This strategy will provide new insight into semiconductor-based fuel cell technology to design novel electrolytes.

Multiscale confinement nitridation in molybdenum carbide for efficient hydrogen production

The molybdenum carbide(Mo_(2)C)has been regarded as one of the most cost-efficient and stable electrocatalyst for the hydrogen evolution reaction(HER)by the virtue of its Pt-like electronic structures.However,the inherent limitation of high density of empty valence band significantly reduces its catalytic reactivity by reason of strong hydrogen desorption resistance.Herein,we propose a multiscale confinement synthesis method to design the nitrogen-rich Mo_(2)C for modulating the band structure via decomposing the pre-coordination bonded polymer in a pressure-tight tube sealing system.Pre-bonded c/N-Mo in the coordination precursor constructs a micro-confinement space,enabling the homogeneous nitrogenization in-situ happened during the formation of Mo_(2)C.Simultaneously,the evolved gases from the precursor decomposition in tube sealing system establish a macro-confinement environment,preventing the lattice N escape and further endowing a continuous nitridation.Combining the multiscale confinement effects,the nitrogen-rich Mo2C displays as high as 25%N-Mo concentration in carbide lattice,leading to a satisfactory band structure.Accordingly,the constructed nitrogen-rich Mo_(2)C reveals an adorable catalytic activity for HER in both alkaline and acid solution.It is anticipated that the multiscale confinement synthesis strategy presents guideline for the rational design of electrocatalysts and beyond.

Electronic structures and energy band properties of Be- and S-doped wurtzite ZnO

The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap semiconductor, the valence band maximum （VBM） and the conduction band minimum （CBM） of BexZn1-xO1-ySy are dominated by S 3p and Zn 4s states, respectively. The band gap and lattice constant of BexZn1-xO1-ySy alloy can be modulated by changing the doped content values x and y. With the increase in Be content value x in the BexZnl-xOl-ySy alloy, the band gap increases and the lattice constant reduces, but the situation is just the opposite when increasing the S content value y in the BexZn1-xO1-ySy alloy. Because the lattice constant of Be0.375Zn0.625O0.75S0.25 alloy is well matched with that of ZnO and its energy gap is large compared with that of ZnO, so the Be0.375Zn0.625O0.75S0.25 alloy is suitable for serving as the blocking material for a high-quality ZnO-based device.

Regulation of excitation energy transfer in Sb-alloyed Cs_(4)MnBi_(2)Cl_(12) perovskites for efficient CO_(2) photoreduction to CO and water oxidation toward H_(2)O_(2)

Lead(Pb)-free halide perovskites have recently attracted increasing attention as potential catalysts for CO_(2) photoreduction to CO due to their potential to capture solar energy and drive catalytic reaction.However,issues of the poor charge transfer still remain one of the main obstacles limiting their performance due to the overwhelming radiative and nonradiative charge-carrier recombination losses.Herein,Pb-free Sb-alloyed all-inorganic quadruple perovskite Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12)(0≤x≤1)is synthesized as efficient photocatalyst.By Sb alloying,the undesired relaxation of photogenerated electrons from conduction band to emission centers of[MnCl6]^(4-)is greatly suppressed,resulting in a weakened PL emission and enhanced charge transfer for photocatalyst.The ensuing Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12) photocatalyst accomplishes efficient conversion of CO_(2)into CO,accompanied by a surprising production of H_(2)O_(2),a high valueadded product associated with water oxidation.By optimizing Sb^(3+) concentration,a high CO evolution rate of 35.1μmol g^(-1)h^(-1)is achieved,superior to most other Pb and Pb-free halide perovskites.Our findings provide new insights into the mixed-cation alloying strategies for improved photocatalytic performance of Pb-free perovskites and shed light on the rational design of robust band structure toward efficient energy transfer.

Strain induced polymorphism and band structure modulation in low-temperature 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene single crystal

Organic semiconductors are inherently soft,making it possible to increase their mobilities by strains.Such a unique feature can be exploited directly in flexible electronics for improved device performance.The 2,7-dioctyl[1]benzothieno[3,2-b][1]-benzothiophene derivative,C8-BTBT is one of the best small-molecule hole transport materials.Here,we demonstrated its band structure modulation under strains by combining the non-equilibrium molecular dynamics simulations and first-principles calculations.We found that the C8-BTBT lattice undergoes a transition from monoclinic to triclinic crystal system at the temperature below 160 K.Both shear and uniaxial strains were applied to the low-temperature triclinic phase of C8-BTBT,and polymorphism was identified in the shear process.The band width enhancement is up to 8%under 2%of compressive strain along the x direction,and 14%under 4%of tensile strain along the y direction.The band structure modulation of C8-BTBT can be well related to its herringbone packing motifs,where the edge to face and edge to edge pairs constitute two-dimensional charge transport pathways and their electronic overlaps determine the band widths along the two directions respectively.These findings pave the way for utilizing strains towards improved performance of organic semiconductors on flexible substrates,for example,by bending the substrates.

Enhancing solar-driven overall water splitting via both sacrifice and noble metal free photocatalysis: copper cluster/boron-doped carbon nitride catalysts

The major impediment to the additional industrialization of water splitting is the high cost of the co-catalyst made of noble metals and the sacrificial reagent. A binary photocatalytic system, consisting of B-doped g-C_(3)N_(4) nanosheets(Cu_(20)@BCN-X) and atomically accurate copper clusters, is designed in this study. The copper clusters serve as co-catalysts for H_(2) evolution and exhibit Pt-like activity, whereas the nanosheets serve as carriers and semiconductor components for O_(2) evolution. Such binary system, created using simple techniques, demonstrates hydrogen bonding interactions that promote synergistic effects and efficient binding and charge transfer across the interface between the two components. Band position manipulation of carbon nitride nanosheets demonstrates a Z-scheme charge transfer mechanism between the nanosheets and copper clusters. This photocatalytic system can accomplish the photocatalytic overall water splitting process(259.9 μmol g^(-1)h^(-1)of H_(2) and 129.4 μmol g^(-1)h^(-1)of O_(2)) without using sacrificial agents or noble metal co-catalysts. This work lays the foundation for the design of overall water splitting catalysts by precisely manipulating the energy levels, and it also paves the way for commercialized photocatalytic catalysts that do not require noble metals or sacrificial chemicals.

Characterization of Full-WDM-Band Photodiode Modules Using Raman Amplifiers in the U Band at 40 Gb/s

We present the characteristics of a full-WDM-band photodiode module in 40 Gb/s U-band operation using a Raman amplifier. This module is suitable for wide-band transmission systems with the additional new channels in the U band.

Vacancy defect engineering in semiconductors for solar light‐driven environmental remediation and sustainable energy production

The introduction of vacancy defects in semiconductors has been proven to be a highly effective approach to improve their photocatalytic activity owing to their advantages of promoting light absorption,facilitating photogenerated carrier separation,optimizing electronic structure,and enabling the production of reactive radicals.Herein,we outline the state-of-the-art vacancy-engineered photocatalysts in various applications and reveal how the vacancies influence photocatalytic performance.Specifically,the types of vacancy defects,the methods for tailoring vacancies,the advanced characteri-zation techniques,the categories of photocatalysts with vacancy defects,and the corresponding photocatalytic behaviors are presented.Meanwhile,the methods of vacancies creation and the related photocatalytic performance are correlated,which can be very useful to guide the readers to quickly obtain in-depth knowledge and to have a good idea about the selection of defect engineering methods.The precise characterization of vacancy defects is highly challenging.This review describes the accurate use of a series of characterization techniques with detailed comments and suggestions.This represents the uniqueness of this comprehensive review.The challenges and development prospects in engineering photocatalysts with vacancy defects for practical applications are discussed to provide a promising research direction in this field.

Micro EEG/ECG signal's chopper-stabilization amplifying chip for novel drycontact electrode

Facing the body＇s EEG（electroencephalograph, 0.5–100 Hz, 5–100 μV） and ECG＇s（electrocardiogram,〈 100 Hz, 0.01–5 mV） micro signal detection requirement, this paper develops a pervasive application micro signal detection ASIC chip with the chopping modulation/demodulation method. The chopper-stabilization circuit with the RRL（ripple reduction loop） circuit is to suppress the ripple voltage, which locates at the single-stage amplifier＇s outputting terminal. The single-stage chopping core＇s noise has been suppressed too, and it is beneficial for suppressing noises of post-circuit. The chopping core circuit uses the PFB（positive feedback loop） to increase the inputting resistance, and the NFB（negative feedback loop） to stabilize the 40 dB intermediate frequency gain. The cascaded switch-capacitor sample/hold circuit has been used for deleting spike noises caused by non-ideal MOS switches, and the VGA/BPF（voltage gain amplifier/band pass filter） circuit is used to tune the chopper system＇s gain/bandwidth digitally. Assisted with the designed novel dry-electrode, the real test result of the chopping amplifying circuit gives some critical parameters： 8.1 μW/channel, 0.8 μVrms（@band-widthD100 Hz）, 4216–11220 times digitally tuning gain range, etc. The data capture system uses the NI CO＇s data capturing DAQmx interface,and the captured micro EEG/ECG＇s waves are real-time displayed with the PC-Labview. The proposed chopper system is a unified EEG/ECG signal＇s detection instrument and has a critical real application value.