2D CoOOH Sheet-Encapsulated Ni2P into Tubular Arrays Realizing 1000 mA cm^-2-Level-Current-Density Hydrogen Evolution Over 100 h in Neutral Water

Water electrolysis at high current density(1000 mA cm-2 level)with excellent durability especially in neutral electrolyte is the pivotal issue for green hydrogen from experiment to industrialization.In addition to the high intrinsic activity determined by the electronic structure,electrocatalysts are also required to be capable of fast mass transfer(electrolyte recharge and bubble overflow)and high mechanical stability.Herein,the 2D CoOOH sheet-encapsulated Ni2P into tubular arrays electrocatalytic system was proposed and realized 1000 mA cm-2-levelcurrent-density hydrogen evolution over 100 h in neutral water.In designed catalysts,2D stack structure as an adaptive material can buffer the shock of electrolyte convection,hydrogen bubble rupture,and evolution through the release of stress,which insure the long cycle stability.Meanwhile,the rich porosity between stacked units contributed the good infiltration of electrolyte and slippage of hydrogen bubbles,guaranteeing electrolyte fast recharge and bubble evolution at the high-current catalysis.Beyond that,the electron structure modulation induced by interfacial charge transfer is also beneficial to enhance the intrinsic activity.Profoundly,the multiscale coordinated regulation will provide a guide to design high-efficiency industrial electrocatalysts.

Nanopore-rich NiFe LDH targets the formation of the high-valent nickel for enhanced oxygen evolution reaction

Nickel-iron layered double hydroxides(NiFe LDHs)represent a promising candidate for oxygen evolution reaction(OER),however,are still confronted with insufficient activity,due to the slow kinetics of electrooxidation of Ni^(2+)cations for the high-valent active sites.Herein,nanopore-rich NiFe LDH(PR-NiFe LDH)nanosheets were proposed for enhancing the OER activity together with stability.In the designed catalyst,the confined nanopores create abundant unsaturated Ni sites at edges,and decrease the migration distance of protons down to the scale of their mean free path,thus promoting the formation of high-valent Ni^(3+)/^(4+)active sites.The unique configuration further improves the OER stability by releasing the lattice stress and accelerating the neutralization of the local acidity during the phase transformation.Thus,the optimized PR-NiFe LDH catalysts exhibit an ultralow overpotential of 278 mV at 10 mA∙cm^(−2)and a small Tafel slope of 75 mV∙dec^(−1),which are competitive among the advanced LDHs based catalysts.Moreover,the RP-NiFe LDH catalyst was implemented in anion exchange membrane(AEM)water electrolyzer devices and operated steadily at a high catalytic current of 2 A over 80 h.These results demonstrated that PR-NiFe LDH could be a viable candidate for the practical electrolyzer.This concept also provides valuable insights into the design of other catalysts for OER and beyond.

Multi-scale regulation in S,N co-incorporated carbon encapsulated Fe-doped CO_(9)S_(8) achieving efficient water oxidation with low overpotential

Sulfide compounds provide a type of promising alternative for oxygen evolution reaction(OER)electrocatalysts due to their diversity,intrinsic activities,low-price and earth-abundance.However,the unsmooth mass transport channel,the collapse of the structure and insufficient intrinsic activities limit their potential for OER performance.In respond,the dense Fe-doped Co_(9)S_(8) nanoparticles encapsulated by S,N co-incorporated carbon nanosheets(Fe-Co_(9)S_(8)@SNC)were proposed and synthesized via fast thermal treatment from ultrathin metal-organic frameworks(MOFs)nanosheets.In designed catalysts,the nanosheet configuration connected by nanoparticles retained rich access for permeation of electrolyte and precipitation of O_(2) bubbles during OER process.Meanwhile,the outer carbon layer of Co9S8 provided additional catalytic activity while acting as armor to keep the structure stability.At the atomic scale,the doped Fe regulated the local charge density and the d-band center for facilitating desorption of oxygen intermediates.Benefiting from this multi-scale regulation strategy,the Fe-Co_(9)S_(8)@SNC displays an ultralow overpotential of 273 mV at 10 mA·cm^(-2) and small Tafel slope of 55.8 mV·dec^(-1),which is even close to the benchmark RuO_(2) catalyst.This concept could provide valuable insights into the design of other catalysts for OER and beyond.

Inversion symmetry broken 2D SnP_(2)S_(6) with strong nonlinear optical response

Nowadays,realizing miniaturized nonlinear optical(NLO)device is crucial to meet the growing needs in on-chip nanophotonics as well as compact integrated devices.The strong optical nonlinearities,ultrafast photoexcitation dynamics,available exciton effects as well as without lattice matching make two-dimensional(2D)layered materials potential candidates for integrated and nano-scale NLO devices.Herein,a novel and inversion symmetry broken 2D layered SnP_(2)S_(6)with strong second-harmonic and third-harmonic response has been reported for the first time.The second-order susceptibility(χ^(2))of SnP_(2)S_(6)flakes can reach up to 4.06×10^(−9)m·V^(−1)under 810 nm excitation wavelength,which is around 1–2 orders of magnitude higher than that of most reported 2D materials.In addition,the NLO response of 2D SnP_(2)S_(6)can break through the limitation of odd/even layers and exhibit broadband spectral response.Moreover,since the second-harmonic signal is closely related to structure variation,the second-harmonic response in 2D SnP_(2)S_(6)is extremely sensitive to polarization angle and temperature,which is beneficial to some specific applications.The excellent NLO response in 2D SnP_(2)S_(6)provides a new arena for realizing miniaturized NLO devices in the future.