Fe-N_(x) sites coupled with core-shell FeS@C nanoparticles to boost the oxygen catalysis for rechargeable Zn-air batteries

The development of efficient single-atom catalysts(SACs) for the oxygen reduction reaction(ORR)remains a formidable challenge,primarily due to the symmetric charge distribution of metal singleatom sites(M-N_(4)).To address such issue,herein,Fe-N_(x) sites coupled synergistic catalysts fabrication strategy is presented to break the uniform electronic distribution,thus enhancing the intrinsic catalytic activity.Precisely,atomically dispersed Fe-N_(x) sites supported on N/S-doped mesoporous carbon(NSC)coupled with FeS@C core-shell nanoparticles(FAS-NSC@950) is synthesized by a facile hydrothermal reaction and subsequent pyrolysis.Due to the presence of an in situ-grown conductive graphitic layer(shell),the FeS nanoparticles(core) effectively adjust the electronic structure of single-atom Fe sites and facilitate the ORR kinetics via short/long-range coupling interactions.Consequently,FAS-NSC@950displays a more positive half-wave potential(E_(1/2)) of 0.871 V with a significantly boosted ORR kinetics(Tafel slope=52.2 mV dec^(-1)),outpacing the commercial Pt/C(E_(1/2)=0.84 V and Tafel slope=54.6 mV dec^(-1)).As a bifunctional electrocatalyst,it displays a smaller bifunctional activity parameter(ΔE) of 0.673 V,surpassing the Pt/C-RuO_(2) combination(ΔE=0.724 V).Besides,the FAS-NSC@950-based zincair battery(ZAB) displays superior power density,specific capacity,and long-term cycling performance to the Pt/C-Ir/C-based ZAB.This work significantly contributes to the field by offering a promising strategy to enhance the catalytic activity of SACs for ORR,with potential implications for energy conversion and storage technologies.

A high‐performance transition‐metal phosphide electrocatalyst for converting solar energy into hydrogen at 19.6% STH efficiency

The construction of high-efficiency and low-cost non-noble metal bifunctional electrocatalysts for water electrolysis is crucial for commercial large-scale application of hydrogen energy.Here,we report a novel strategy with erbiumdoped NiCoP nanowire arrays in situ grown on conductive nickel foam(Er-NiCoP/NF).Significantly,the developed electrode shows exceptional bifunctional catalytic activity,which only requires overpotentials of 46 and 225 mV to afford a current density of 10 mAcm^(−2) for the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER),respectively.Density functional theory calculations reveal that the appropriate Er incorporation into the NiCoP lattice can significantly modulate the electronic structure with the d-band centers of Ni and Co atoms by shifting to lower energies with respect to the Fermi level,and optimize the Gibbs free energies of HER/OER intermediates,thereby accelerating water-splitting kinetics.When assembled as a solar-driven overall water-splitting electrolyzer,the as-prepared electrode shows a high and stable solar-to-hydrogen efficiency of 19.6%,indicating its potential for practical storage of intermittent energy.

Heterostructured bimetallic phosphide nanowire arrays with latticetorsion interfaces for efficient overall water splitting

Designing cost-effective and high-efficiency electrocatalysts is critical to the water splitting performance during hydrogen generation.Herein,we have developed Fe_(2)P-Co_(2)P heterostructure nanowire arrays with excellent lattice torsions and grain boundaries for highly efficient water splitting.According to the microstructural investigations and theoretical calculations,the lattice torsion interface not only contributes to the exposure of more active sites but also effectively tunes the adsorption energy of hydrogen/oxygen intermediates via the accumulation of charge redistribution.As a result,the Fe_(2)P-Co_(2)P heterostructure nanowire array exhibits exceptional bifunctional catalytic activity with overpotentials of 65 and 198 mV at 10 mA cm^(-2) for hydrogen and oxygen evolution reactions,respectively.Moreover,the Fe_(2)P-Co_(2)P/NF-assembled electrolyzer can deliver 10 mA cm^(-2) at an ultralow voltage of1.51 V while resulting in a high solar-to-hydrogen conversion efficiency of 19.8%in the solar-driven water electrolysis cell.

Experimental study on the cavity evolution and liquid spurt of hydrodynamic ram

In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted. The relationships between the above three characteristics have been researched. The evolution of the cavity can be divided into three processes according to its shape characteristics. The first liquid spurt occurred in Process Ⅱ and the rest of it occurred in Process Ⅲ. The duration of the second liquid spurt is longer than the first liquid spurt. When the impact velocity of the fragment is less than996 m/s, the velocity of the second liquid spurt is the highest. When the velocity of the fragment is greater than 996 m/s, the velocity of the first liquid spurt is the highest. The maximum velocities of the first and second liquid spurt are 111 m/s and 94 m/s respectively. The pressure fluctuated sharply in Processes Ⅰ and Ⅲ. The maximum peak pressures in the shock and the cavity oscillation phases are15.51 MPa and 7.96 MPa respectively. The time interval of the two adjacent pressure pulses increases with the increase of the fragment velocity.

Environmentally persistent free radicals in PM_(2.5):a review

Environmentally persistent free radicals(EPFRs)are a new class of pollutants that are long-lived in fine particles(PM_(2.5)),i.e.,their 1/e lifetime ranges from days to months(or even infinite).They are capable of producing harmful reactive oxygen species such as hydroxyl radicals.The redox cycling of EPFRs is considered as an important pathway for PM_(2.5) to induce oxidative stress inside the humans,causing adverse health effects such as respiratory and cardiovascular diseases.Conse-quently,research regarding their toxicity,formation and environmental occurrences in PM_(2.5) has attracted increasing atten-tions globally during the past two decades.However,literature data in this field remain quite limited and discrete.Hence,an extensive review is urgently needed to summarize the current understanding of this topic.In this work,we systematically reviewed the analytical methods and environmental occurrences,e.g.,types,concentrations,and decay behaviors,as well as possible sources of EPFRs in PM_(2.5).The types of pretreatment methods,g-values of common EPFRs and categories of decay processes were discussed in detail.Moreover,great efforts were made to revisit the original data of the published works of EPFRs in airborne particulate matter and provided additional useful information for comparison where possible,e.g.,their mean and standard deviation of g-values,line widths(ΔHp-p),and concentrations.Finally,possible research opportunities were highlighted to further advance our knowledge of this emerging issue.