The modulation of catalytic active site and support to construct high-efficiency ZnS/NC-X electrocatalyst for nitrogen reduction

Transition metals are a kind of promising catalysts to apply into electrocatalytic synthesis ammonia by virtue of abundant reserves and low cost.However,many widely used transition metal catalysts usually face the challenge to realize satisfactory catalytic results mainly resulting from the match between catalytic active site and support.Here,a new-type ZnS/NC-X electrocatalyst was reported by in-situ sulfidation of zeolitic imidazolate framework-8(ZIF-8),where the metal nodes of ZIF-8 reacted with dibenzyl disulfide(BDS)to obtain ZnS nanoparticles and the framework of ZIF-8 was carbonized to form the support.Especially,catalytic active sites(ZnS nanoparticles)and support(NC-X)were adjusted in detailed by changing the ratio of ZIF-8 and BDS.As a result,when the mass ratio of ZIF-8 and BDS was 1:1,the resulted ZnS/NC-2 catalyst achieved a remarkable NH3 yield of 65.60μg·h^(−1)·mg^(−1)cat.,Faradaic efficiency(FE)of 18.52%at−0.4 V vs reversible hydrogen electrode(RHE)in 0.05 M H2SO4 and catalytic stability,which outperformed most reported transition metal sulfides.The matching catalytic active site and support make our strategy promising for wide catalytic applications.

Effect of noble metal nanoparticle size on C–N bond cleavage performance in hydrodenitrogenation: a study of active sites

Breakage of the C-N bond is a structure sensitive process,and the catalyst size significantly affects its activity.On the active metal nanoparticle scale,the role of catalyst size in C-N bond cleavage has not been clearly elucidated.So,Ru catalysts with variable nanoparticle sizes were obtained by modulating the reduction temperature,and the catalytic activity was evaluated using 1,2,3,4-tetrahydroquinoline and o-propylaniline with different C-N bond hybridization patterns as reactants.Results showed a 13 times higher reaction rate for sp3-hybridized C-N bond cleavage than sp2-hybridized C-N bond cleavage,while the reaction rate tended to increase first and then decrease as the catalyst nanoparticle size increased.Different concentrations of terrace,step,and corner sites were found in different sizes of Ru nanoparticles.The relationship between catalytic site variation and C-N bond cleavage activity was further investigated by calculating the turnover frequency values for each site.This analysis indicates that the variation of different sites on the catalyst is the intrinsic factor of the size dependence of C-N bond cleavage activity,and the step atoms are the active sites for the C-N bond cleavage.When Ru nanoparticles are smaller than 1.9 nm,they have a strong adsorption effect on the reactants,which will affect the catalytic performance of the Ru catalyst.Furthermore,these findings were also confirmed on other metallic Pd/Pt catalysts.The role of step sites in C-N bond cleavage was proposed using the density function theory calculations.The reactants have stronger adsorption energies on the step atoms,and step atoms have d-band center nearer to the Fermi level.In this case,the interaction with the reactant is stronger,which is beneficial for activating the C-N bond of the reactant.

Identification and comparison of the local physicochemical structures of transition metal-based layered double hydroxides for high performance electrochemical oxygen evolution reactions

Layered double hydroxides(LDHs) have attracted considerable attention as a cost effective alternative to the precious iridium-and ruthenium-based electrocatalysts for an oxygen evolution reaction(OER),a bottleneck of water electrolysis for sustainable hydrogen production.Despite their excellent OER performance,the structural and electronic properties of LDHs,particularly during the OER process,remain to be poorly understood.In this study,a series of LDH catalysts is investigated through in situ X-ray absorption fine structure analyses and density functional theory(DFT) calculations.Our experimental results reveal that the LDH catalyst with equal amounts of Ni and Fe(NF-LDH) exhibits the highest OER activity and catalytic life span when compared with its counterparts having equal amounts of Ni and Co(NC-LDH)and Ni only(Ni-LDH).The NF-LDH shows a markedly enhanced OER kinetics compared to the NC-LDH and the Ni-LDH,as proven by the lower overpotentials of 180,240,and 310 mV,respectively,and the Tafel slopes of 35.1,43.4,and 62.7 mV dec^(-1),respectively.The DFT calculations demonstrate that the lowest overpotential of the NF-LDH is associated with the active sites located at the edge planes of NF-LDH in contrast to those located at the basal planes of Ni-LDH and NC-LDH.The current study pinpoints the active sites on various LDHs and presents strategies for optimizing the OER performance of the LDH catalysts.

Enhanced hydrogen evolution from the face-sharing[RuO6]octahedral motif

Hampered by the ambiguous mechanism of hydrogen evolution reaction(HER)in basic media,the exploration of highly efficient catalytically active sites for alkaline HER is of significance.Herein,a metal oxide Sr_(4)Ru_(2)O_(9)engineering a face-sharing[RuO_(6)]octahedra motif was synthesized through the solid-state method,and served as HER electrocatalyst.Benefited from the Ru-Ru metallic bonding crossing the common plane,the H*adsorption and reaction energy barriers were optimized.Sr_(4)Ru_(2)O_(9)only required an ultra-small overpotential(η10)of 28 m V at a current density of 10 mA cm^(-2) for HER in 1.0 M KOH with an exceptional stability(180 hours),outperforming the commercial Pt/C(η10=38 mV).These findings suggest a fresh insight in designing novel active sites for electrocatalysis.

Two distant catalytic sites are responsible for C2c2 RNase activities

Subject Code:C05 With the support by the National Natural Science Foundation of China,the research team led by Prof.Wang Yanli(王艳丽)at the Key Laboratory of RNA Biology&CAS Center for Excellence in Biomacromolecules,Institute of Biophysics,Chinese Academy of Sciences,recently reported that CRISPRC2c2protein has two distant catalytic sites responsible for its dual RNase activities in Cell(2017,168:121—134).