A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the f...A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the ferrimagnetic matrix.Additionally,the exchange bias effect is gradually pronounced with the positive increase in the cooling field,known as the conventional exchange bias effect.However,as the cooling field gradually decreases and transits from positive to negative,the exchange bias effect can robustly remain positive in the low-negative-field region until the cooling field increases to be sufficiently large in the negative direction.展开更多
The synergy of single atoms(SAs)and nanoparticles(NPs)has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR);however,the rationalization of the SAs/NPs proportio...The synergy of single atoms(SAs)and nanoparticles(NPs)has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR);however,the rationalization of the SAs/NPs proportion remains one challenge for the catalyst design.Herein,a Ni2+-loaded porous poly(ionic liquids)(PIL)precursor synthesized through the free radical self-polymerization of the ionic liquid monomer,1-allyl-3-vinylimidazolium chloride,was pyrolyzed to prepare the Ni,N co-doped carbon materials,in which the proportion of Ni SAs and NPs could be facilely modulated by controlling the annealing temperature.The catalyst Ni-NC-1000 with a moderate proportion of Ni SAs and NPs exhibited high efficiency in the electrocatalytic conversion of CO_(2)into CO.Operando Ni K-edge X-ray absorption near-edge structure(XANES)spectra and theoretical calculations were conducted to gain insight into the synergy of Ni SAs and NPs.The charge transfer from Ni NPs to the surrounding carbon layer and then to the Ni SAs resulted in the electron-enriched Ni SAs active sites.In the electroreduction of CO_(2),the coexistence of Ni SAs and NPs strengthened the CO_(2)activation and the affinity towards the key intermediate of*COOH,lowering the free energy for the potential-determining*CO_(2)→*COOH step,and therefore promoted the catalysis efficiency.展开更多
Photocatalytic hydrogen(H_(2))production from seawater over a photocatalyst is of great significance for the utilization of the earth’s abundant seawater resources and the storage of inexhaustible solar energy with l...Photocatalytic hydrogen(H_(2))production from seawater over a photocatalyst is of great significance for the utilization of the earth’s abundant seawater resources and the storage of inexhaustible solar energy with low-energy density.However,the designation of efficient photocatalytic systems by using seawater usually suffers from activation decline when replacing pure water with seawater.Herein,we synthesized threeβ-ketoenamine-linked covalent organic frameworks(COFs),demonstrating their promotion in the photocatalytic decomposition of seawater relative to pure water under visible-light irradiation.The target COFs were synthesized via a microwave assisted solvothermal method by using 1,3,5-triformylphloroglucinol(Tp)as the aldehyde monomer to react with diamino units with different numbers of benzene rings.By surveying the building blocks,the constructed COF with a high density ofβ-ketoenamine units exhibited the so far highest photocatalytic H_(2) evolution rate(41.3 mmol·g^(−1)·h^(−1))in seawater,about 1.66 times higher than that in pure water.Theβ-ketoenamine units allowed the in-situ polarization of the COF framework through the adsorption of metal salts when proceeding with the photocatalytic H_(2) production in seawater.This polarization effect significantly increases the dielectric constant of the organic semiconductor to lower exciton dissociation energy and thus enhances the charge separation and transfer to promote the H_(2) photoproduction in seawater.展开更多
Finely adjusting the local environment of Cu single atom(SA)is crucial but challenging for the fabrication of electrocatalysts for the CO_(2)reduction reaction(CO_(2)RR)to produce clean energy methane(CH_(4)).Herein,p...Finely adjusting the local environment of Cu single atom(SA)is crucial but challenging for the fabrication of electrocatalysts for the CO_(2)reduction reaction(CO_(2)RR)to produce clean energy methane(CH_(4)).Herein,poly(ionic liquid)s-stabilized Cu SAs with tunable Br-Cu-Cx configuration were directly synthesized through the self-polymerization of the ionic liquid monomer,a bis-vinylimidazolium salt,in the presence of Cu precursor.Synchrotron X-ray absorption fine structure,soft X-ray absorption,and X-ray photoelectron spectroscopy analyses showed that the Cu SAs were coordinated with N-heterocyclic carbene derived from the imidazole ring.The optimal catalyst Cu@P-2 with moderate Cu loading afforded a high Faradaic efficiency of∼70%at a high current of-250 mA cm^(-2)in the CO_(2)RR to CH_(4),associating with a turnover frequency as high as 1.0 s^(-1).This outstanding performance is assigned to the high density Cu SAs reaching strong affinity towards*CO intermediates in the case of moderate Cu loading,as revealed by in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy analysis and theoretical calculated free energy profiles of CO_(2)RR to CH_(4).展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.11474111 and 11604281)the Young Elite Scientists Sponsorship Program by CAST(No.YESS20220618)the Hundreds of Talents program of Sun Yat-sen University(No.210192)
文摘A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the ferrimagnetic matrix.Additionally,the exchange bias effect is gradually pronounced with the positive increase in the cooling field,known as the conventional exchange bias effect.However,as the cooling field gradually decreases and transits from positive to negative,the exchange bias effect can robustly remain positive in the low-negative-field region until the cooling field increases to be sufficiently large in the negative direction.
基金National Natural Science Foundation of China(grants 22072065,22178162,and 22222806)Distinguished Youth Foundation of Jiangsu Province(grant BK20220053)Six talent peaks project in Jiangsu Province(grant JNHB-035)。
文摘The synergy of single atoms(SAs)and nanoparticles(NPs)has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR);however,the rationalization of the SAs/NPs proportion remains one challenge for the catalyst design.Herein,a Ni2+-loaded porous poly(ionic liquids)(PIL)precursor synthesized through the free radical self-polymerization of the ionic liquid monomer,1-allyl-3-vinylimidazolium chloride,was pyrolyzed to prepare the Ni,N co-doped carbon materials,in which the proportion of Ni SAs and NPs could be facilely modulated by controlling the annealing temperature.The catalyst Ni-NC-1000 with a moderate proportion of Ni SAs and NPs exhibited high efficiency in the electrocatalytic conversion of CO_(2)into CO.Operando Ni K-edge X-ray absorption near-edge structure(XANES)spectra and theoretical calculations were conducted to gain insight into the synergy of Ni SAs and NPs.The charge transfer from Ni NPs to the surrounding carbon layer and then to the Ni SAs resulted in the electron-enriched Ni SAs active sites.In the electroreduction of CO_(2),the coexistence of Ni SAs and NPs strengthened the CO_(2)activation and the affinity towards the key intermediate of*COOH,lowering the free energy for the potential-determining*CO_(2)→*COOH step,and therefore promoted the catalysis efficiency.
基金the National Natural Science Foundation of China(Nos.22072065,22178162,and 22222806)the Distinguished Youth Foundation of Jiangsu Province(No.BK20220053)the Six Talent Peaks Project in Jiangsu Province(No.JNHB-035).
文摘Photocatalytic hydrogen(H_(2))production from seawater over a photocatalyst is of great significance for the utilization of the earth’s abundant seawater resources and the storage of inexhaustible solar energy with low-energy density.However,the designation of efficient photocatalytic systems by using seawater usually suffers from activation decline when replacing pure water with seawater.Herein,we synthesized threeβ-ketoenamine-linked covalent organic frameworks(COFs),demonstrating their promotion in the photocatalytic decomposition of seawater relative to pure water under visible-light irradiation.The target COFs were synthesized via a microwave assisted solvothermal method by using 1,3,5-triformylphloroglucinol(Tp)as the aldehyde monomer to react with diamino units with different numbers of benzene rings.By surveying the building blocks,the constructed COF with a high density ofβ-ketoenamine units exhibited the so far highest photocatalytic H_(2) evolution rate(41.3 mmol·g^(−1)·h^(−1))in seawater,about 1.66 times higher than that in pure water.Theβ-ketoenamine units allowed the in-situ polarization of the COF framework through the adsorption of metal salts when proceeding with the photocatalytic H_(2) production in seawater.This polarization effect significantly increases the dielectric constant of the organic semiconductor to lower exciton dissociation energy and thus enhances the charge separation and transfer to promote the H_(2) photoproduction in seawater.
基金the funding from the National Natural Science Foundation of China(grant nos.22072065,22178162,and 22222806)the Distinguished Youth Foundation of Jiangsu Province(grant no.BK20220053)+1 种基金the Six Talent Peaks Project in Jiangsu Province(grant no.JNHB-035)Agency for Science,Technology and Research(A*STAR)through Low Carbon Energy Research Finding Initiative(grant nos.LCERFI01-0033 and U2102d2006).
文摘Finely adjusting the local environment of Cu single atom(SA)is crucial but challenging for the fabrication of electrocatalysts for the CO_(2)reduction reaction(CO_(2)RR)to produce clean energy methane(CH_(4)).Herein,poly(ionic liquid)s-stabilized Cu SAs with tunable Br-Cu-Cx configuration were directly synthesized through the self-polymerization of the ionic liquid monomer,a bis-vinylimidazolium salt,in the presence of Cu precursor.Synchrotron X-ray absorption fine structure,soft X-ray absorption,and X-ray photoelectron spectroscopy analyses showed that the Cu SAs were coordinated with N-heterocyclic carbene derived from the imidazole ring.The optimal catalyst Cu@P-2 with moderate Cu loading afforded a high Faradaic efficiency of∼70%at a high current of-250 mA cm^(-2)in the CO_(2)RR to CH_(4),associating with a turnover frequency as high as 1.0 s^(-1).This outstanding performance is assigned to the high density Cu SAs reaching strong affinity towards*CO intermediates in the case of moderate Cu loading,as revealed by in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy analysis and theoretical calculated free energy profiles of CO_(2)RR to CH_(4).
