Bubbles generated during the oxygen evolution reaction(OER)in water splitting readily adhere to the electrode surface,thereby impeding contact between the electrolyte and the active sites,thereby increasing the overpotential.Consequently,it is imperative to elucidate the bubble release behavior and engineer electrodes that facilitate faster bubble release.In this study,inspired by the wood stem of the Norway spruce,we synthesized a gradient nanoporous high-entropy oxide(GNP-HEO)electrode with a controllable pore size.The GNP-HEO,featuring a well-controlled gradient in pore size,is achieved through a straightforward strategy combining selective laser melting with selective phase dissolution.This unique gradient nanoporous structure not only facilitates bubble release but also diminishes the bubble shielding effect in OER,thereby enhancing electrocatalytic performance.The affect interaction of Al,Co,Cr,Fe,and Ni,coupled with the gradient nanoporous structure,yields exceptional OER performance,evidenced by an overpotential of 250 mV at a current density of 50 mA/cm^(2) and a Tafel slope of 38.0 mV/dec in 1 M KOH.Density functional theory calculations confirm that the GNPHEO adheres to the adsorbate evolution mechanism reaction pathway and exhibits significant stability.This work highlights a promising approach for the design and synthesis of high-performance OER electrocatalysts.
Wei WangWeiqi WangHuihui WangXing LuJinwen ZhangYunzhuo Lu
Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation.
The utilization of nanoporous copper(np-Cu)as a metallic actuator has gained attention in recent years due to its cost-effectiveness in comparison to other precious metals.Despite this,the enhancement of np-Cu’s actuation performance remains a challenge due to limitations in its strain amplitude and actuation rate.Additionally,np-Cu has been deemed as a promising material for solar absorption due to its localized surface plasmon resonance effect.However,practical applications such as solar steam generators(SSGs)utilizing np-Cu have yet to be documented.In this study,we present the development of hierarchically nanoporous copper(HNC)through the dealloying of a eutectic Al-Cu alloy.The hierarchical structure of the HNC features a combination of ordered flat channels and randomly distributed continuous nanopores,which work in synergy to improve actuation performance.The ordered flat channels,with a sub-micron scale,facilitate rapid mass transport of electrolyte ions,while the nano-sized continuous pores,due to their large specific surface area,enhance the induced strain.Our results indicate that the HNC exhibits improved actuation performance,with a two times increase in both strain amplitude and rate in comparison to other reported np-Cu.Additionally,the HNC,for the first time,showcases excellent solar steam generation capabilities,with an evaporation rate of 1.47 kg·m^(-2)·h^(-1) and a photothermal conversion efficiency of 92%under a light intensity of 1 kW·m^(-2),which rivals that of nanoporous gold and silver film.The enhanced actuation performance and newly discovered solar steam generation properties of the HNC are attributed to its hierarchically porous structure.
Bulk nanoporous(np)metallic actuators have attracted increasing attention due to their large strain and low stimulation voltage.However,studies focusing upon the combined effect of composition and structure on the actuation performance of metallic actuators are relatively scarce,and its underlying mechanism needs to be clarified Herein,a series of bulk np-NiPd samples with differen compositions and microstructures were fabricated using a dealloying-coarsening-dealloying strategy and chargecontrolled electrochemical dealloying,and the process involves only one component of precursor alloy.It has been found that the np-NiPd cubes show a composition/structure-dependent mechanical property and electrochemical actuation performance.Specially,the npNi_(70)Pd_(30)sample with a homogeneously porous structure and good network connectivity exhibits significantly larger strain amplitude and faster strain rate than other hierarchically porous NiPd samples(np-Ni_(50)Pd_(50)and npNi_(20)Pd_(80)).Moreover,the np-Ni_(70)Pd_(30)sample demonstrates good actuation stability with high strain retention after hundreds of cycles.Notably,the maximum strain amplitude(1.17%)is even comparable to that of advanced leadfree piezoceramic,and the maximum strain rate exceeds those of many reported metallic actuator materials.Our work indicates that good network connectivity plays a vita role in facilitating large/fast strain response in metallic actuators.
由于单金属Bi在CO_(2)还原反应(CO_(2)RR)中效率较低,通过表面工程复合材料提高电导率和产率是一种有吸引力的方法.在此,我们重构了在三维纳米孔铜结构中的原位生长金属Bi纳米颗粒.得益于三维纳米多孔导电网络和Cu与Bi之间的强相互作用,Bi@np-Cu费米能级向上移动,表现出优异的电催化二氧化碳还原性能.Bi@np-Cu在-0.97 V的电位下具有97.7%的甲酸法拉第效率,电流密度为82 mA cm^(-2).重要的是,该催化剂在连续催化反应40 h后仍能实现超过90%的法拉第效率.DFT计算表明,np-Cu有效地调节了Bi的电子态,优化了中间吸附能,从而提高了Bi的本征活性.这项工作为纳米多孔金属在催化中的应用提供了一个新视角.
The exploration of new heterojunction materials is of great significance in reducing the cost of existing noble metal catalysts and thus realizing the large-scale application of electrocatalytic hydrolysis technology.Herein,a novel CoP/CoMoP_(2) heterojunction was synthesized and served as a hydrogen evolution reaction(HER)electrocatalyst.The heterojunction has morphology of nanoporous structure,which is conducive to exposing more active sites and facilitating bubbles transport.The charge distribution is optimized by a strong interface interaction between CoP and CoMoP_(2).The catalyst’s conductivity and the adsorption properties of the intermediates have both been enhanced.CoP/CoMoP_(2) demonstrates excellent HER activity with an overpotential of 93.6 mV at 10 mA∙cm^(-2),which is competitive with the reported performance of analogous electrocatalysts.This work provides insights into the development of innovative phosphide-based heterojunction electrocatalysts.
Intracellular electrophysiological research is vital for biological and medical research.Traditional planar microelectrode arrays(MEAs)have disadvantages in recording intracellular action potentials due to the loose cell-electrode interface.To investigate intracellular electrophysiological signals with high sensitivity,electroporation was used to obtain intracellular recordings.In this study,a biosensing system based on a nanoporous electrode array(NPEA)integrating electrical perforation and signal acquisition was established to dynamically and sensitively record the intracellular potential of cardiomyocytes over a long period of time.Moreover,nanoporous electrodes can induce the protrusion of cell membranes and enhance cell-electrode interfacial coupling,thereby facilitating effective electroporation.Electrophysiological signals over the entire recording process can be quantitatively and segmentally analyzed according to the signal changes,which can equivalently reflect the dynamic evolution of the electroporated cardiomyocyte membrane.We believe that the low-cost and high-performance nanoporous biosensing platform suggested in this study can dynamically record intracellular action potential,evaluate cardiomyocyte electroporation,and provide a new strategy for investigating cardiology pharmacological science.
Fluid flow at nanoscale is closely related to many areas in nature and technology(e.g.,unconventional hydrocarbon recovery,carbon dioxide geo-storage,underground hydrocarbon storage,fuel cells,ocean desalination,and biomedicine).At nanoscale,interfacial forces dominate over bulk forces,and nonlinear effects are important,which significantly deviate from conventional theory.During the past decades,a series of experiments,theories,and simulations have been performed to investigate fluid flow at nanoscale,which has advanced our fundamental knowledge of this topic.However,a critical review is still lacking,which has seriously limited the basic understanding of this area.Therefore herein,we systematically review experimental,theoretical,and simulation works on single-and multi-phases fluid flow at nanoscale.We also clearly point out the current research gaps and future outlook.These insights will promote the significant development of nonlinear flow physics at nanoscale and will provide crucial guidance on the relevant areas.
