Tandem catalysis of Cu/Ni multi-sites promotes oxygen reduction reaction

The special electronic characteristics and high atom usage efficiency of metal-nitrogen-carbon(M-N-C)materials have made them extremely attractive for oxygen reduction reactions(ORRs).However,it is inevitable that hydrogen peroxide(H_(2)O_(2))will be formed via the two-electron pathway in ORRs.Herein,the Cu nanoparticles(NPs)have been encapsulated into Ni doped hollow mesoporous carbon spheres(Ni-HMCS)to reduce the generation of H_(2)O_(2)in ORR.Electrochemical tests confirm that the introduction of Cu NPs improves the ORR performance greatly.The obtained Cu/Ni-HMCS exhibits a half-wave potential of 0.82 V vs.reversible hydrogen electrode and a limited current density of 5.5 mA cm^(-2),which is comparable with the commercial Pt/C.Moreover,Cu/Ni-HMCS has been used in Zn-air battery,demonstrating a high power density of 161 mW cm^(-2)and a long-term recharge capability(50 h at 5 mA cm^(-2)).The theoretical calculation proposes a tandem catalysis pathway for Cu/Ni multi-sites catalysis,that is,H_(2)O_(2)released from the Ni-N_(4)and Cu-N_(4)sites migrates to the Cu(111)face,on which the captive H_(2)O_(2)is further reduced to H_(2)O.This work demonstrates an interesting tandem catalytic pathway of dual-metal multi-sites for ORR,which provides an insight into the development of effective fuel cell electrocatalysts.

Advances in the relationship between coronavirus infection and coagulation function

To the Editor:It is reported that the patients with coronavirus disease 2019(COVID-19)infection who were admitted to the intensive care unit(ICU)had longer prothrombin time and higher plasma D-dimer levels compared to those who were not admitted to the ICU.This indicates that these patients had a higher risk of thromboembolism.In addition,plasma tumor necrosis factor-α(TNF-α)levels in ICU patients were significantly higher than those in non-ICU patients,and plasma TNF-αlevels,interleukin(IL)-1 levels and IL-8 levels in all infected patients were higher than normal.[1]The high expression of these inflammatory cytokines indicates that there is an inflammatory response in infected patients,and the inflammatory response is more obvious in severe patients.