Enhancing hydrogen electrocatalytic oxidation on Ni_(3)N/MoO_(2)in-plane heterostructures in alkaline solution

Nickel(Ni)-based materials act as one of the most promising candidates as platinum-group-metal-free(PGM-free)electrocatalysts for hydrogen oxidation reaction(HOR)in alkaline solution.Nevertheless,the electrocatalytic activity of pure Ni is significantly limited due to the sluggish kinetics under alkaline condition.To accelerate the kinetics,constructing heterostructures and nitride structures have been developed as two representative strategies.Here,we combined the two methods and presented a facile synthesis of the sheet-like Ni_(3)N/MoO_(2)in-plane heterostructures for enhanced HOR in alkaline electrolytes.Relative to Ni or Ni_(3)N,the Ni_(3)N/MoO_(2)in-plane heterostructures exhibited a significantly increased mass activity by 8.6-fold or 4.4-fold,respectively.Mechanistic studies revealed that the enhanced activity of Ni_(3)N/MoO_(2)could be attributed to the weakened hydrogen adsorption and strengthened hydroxyl adsorption.This work provides a facile approach to design high-efficiency catalysts for hydrogen-oxidation catalysis and beyond.

阿秒光脉冲:照亮通往物质内部电子世界的道路

物理学始于对物质运动本质的哲学探索,而现代物理学则开端于对运动过程的定量实验测量.无论是速度还是加速度,这些最简单的物理量的定义都与时间密不可分.随着人类探索自然的脚步进入微观世界,就需要在更快的时间尺度上对微观粒子的运动过程进行观测,其根本原因在于越是处于基本层面的微观粒子,其特征运动时间越快.

FD-SWIPT双向中继系统中基于天线选择与波束成形联合优化的高能效和吞吐量最大化方案

本文考虑了一个利用full-duplex simultaneous wireless information and power transfer (FDSWIPT)双向中继提供移动通信蜂窝网络中小区覆盖,同时改进吞吐量和能量效率的应用场景.针对FD-SWIPT双向中继研究存在问题,提出了FD-SWIPT双向中继系统中基于天线选择与波束成形联合优化的高能效和吞吐量最大化方案.首先,给出了一种低复杂度次优天线分组算法,在中继接收端使用天线分组策略,将信道条件好的接收信号用于传输,剩下的信号用于能量采集.进一步,在中继发送端设计了波束成形方案,并利用最大广义特征值方法优化波束成形矢量,达到优化接收端信干噪比的目的.仿真结果表明,所提出的联合优化方案能有效提升系统的和吞吐量与能量效率,且天线选择方案起到了重要的作用.

A Custom-Tailored Multi-TW Optical Electric Field for Gigawatt Soft-X-Ray Isolated Attosecond Pulses

Since the first isolated attosecond pulse was demonstrated through high-order harmonics generation(HHG)in 2001,researchers’interest in the ultrashort time region has expanded.However,one realizes a limitation for related research such as attosecond spectroscopy.The bottleneck is concluded to be the lack of a high-peak-power isolated attosecond pulse source.Therefore,currently,generating an intense attosecond pulse would be one of the highest priority goals.In this paper,we review our recent work of a TW-class parallel three-channel waveform synthesizer for generating a gigawatt-scale soft-X-ray isolated attosecond pulse(IAP)using HHG.By employing several stabilization methods,we have achieved a stable 50 mJ three-channel opticalwaveform synthesizer with a peak power at the multi-TW level.This optical-waveform synthesizer is capable of creating a stable intense optical field for generating an intense continuum harmonic beam thanks to the successful stabilization of all the parameters.Furthermore,the precision control of shot-to-shot reproducible synthesized waveforms is achieved.Through the HHG process employing a loose-focusing geometry,an intense shot-to-shot stable supercontinuum(50–70 eV)is generated in an argon gas cell.This continuum spectrum supports an IAP with a transform-limited duration of 170 as and a submicrojoule pulse energy,which allows the generation of a GW-scale IAP.Another supercontinuum in the soft-X-ray region with higher photon energy of approximately 100–130 eV is also generated in neon gas from the synthesizer.The transform-limited pulse duration is 106 as.Thus,the enhancement of HHG output through optimized waveform synthesis is experimentally proved.

Snapshot coherent diffraction imaging across ultra-broadband spectra

Ultrafast imaging simultaneously pursuing high temporal and spatial resolution is a key technique to study the dynamics in the microscopic world.However,the broadband spectra of ultra-short pulses bring a major challenge to traditional coherent diffraction imaging(CDI),as they result in an indistinct diffraction pattern,thereby complicating image reconstruction.To address this,we introduce,to our knowledge,a new ultrabroadband coherent imaging method,and empirically demonstrate its efficacy in facilitating high-resolution and rapid image reconstruction of achromatic objects.The existing full bandwidth limitation for snapshot CDI is enhanced to∼60%experimentally,restricted solely by our laser bandwidth.Simulations indicate the applicability of our method for CDI operations with a bandwidth as high as∼140%,potentially supporting ultrafast imaging with temporal resolution into∼50-attosecond scale.Even deployed with a comb-like harmonic spectrum encompassing multiple octaves,our method remains effective.Furthermore,we establish the capability of our approach in reconstructing a super-broadband spectrum for CDI applications with high fidelity.Given these advancements,we anticipate that our method will contribute significantly to attosecond imaging,thereby advancing cutting-edge applications in material science,quantum physics,and biological research.