Fe–N–C single atom catalysts for the electrochemical conversion of carbon,nitrogen and oxygen elements

Single atom catalysts(SACs)are constituted by isolated active metal centers,which are heterogenized on inert supports such as graphene,porous carbon,and amorphous carbon.The thermal stability,electronic properties,and catalytic activities of the metal center can be controlled via manipulating the neighboring heteroatoms such as nitrogen,oxygen,and sulfur.Due to the atomical dispersion of the active catalytic centers,the amount of metal required for catalysis can be decreased.Furthermore,new possibilities are offered to easily control the selectivity of a given transformation process as well as to improve turnover frequencies and turnover numbers of target reactions.Among them,Fe–N–C single atom catalysts own special electronic structure,and have been widely used in many fields of electrocatalysis.This review aims to summarize the synthesis of Fe–N–C based on anchoring individual iron atoms on carbon/graphene.The spin-related properties of Fe–N–C catalysts are described,including the relation between spin and electron structure of Fe–N x as well as the coupling between electronic structure of Fe–N x and electronic(orbit)of CO_(2),N_(2)and O_(2).Next,mechanistic investigations conducted to un-derstand the specific behavior of Fe–N–C catalysts are highlighted,including C,N,O electro-reduction.Finally,some issues related to the future developments of Fe–N–C are put forward and corresponding feasible solutions are offered.

Promoting Electrocatalytic CO_(2) Reduction to CO via Sulfur-Doped Co-N-C Single-Atom Catalyst

Electrocatalytic reduction of CO_(2) to fuels and chemicals possesses huge potential to alleviate current environmental crisis.Heteroatom doping in metal-nitrogen-carbon(M-N-C)single-atom catalysts(SACs)has been found to be capable to promote the electrocatalytic CO_(2) reduction reaction(CO_(2)RR).However,the origin of the enhanced activity is still elusive.Here,we report that sulfur-doped cobalt-nitrogen-carbon single-atom catalyst(Co1-SNC)exhibits superior CO_(2)RR performance compared to sulfur-free counterpart(Co1-NC).On the basis of in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS),kinetic isotope effect(KIE)and theoretical calculation,it is demonstrated that sulfur doping can promote water activation,elevate the d-band center of Co active site,and reduce the free energy of*COOH intermediate formation.This work deepens the understanding of the CO_(2)RR chemistry over heteroatom-doped SACs for designing efficient CO_(2)RR processes.

Pt_(1)/Ni_(6)Co_(1)layered double hydroxides/N-doped graphene for electrochemical non-enzymatic glucose sensing by synergistic enhancement of single atoms and doping

The development of novel single-atom catalysts is important for highly efficient electrochemical catalysis and sensing.In this work,a novel Pt single atoms(SAs)supported on Ni_(6)Co_(1)layered double hydroxides/nitrogen-doped graphene(Pt_(1)/Ni_(6)Co_(1)LDHs/NG)was constructed for electrochemical enzyme-free catalysis and sensing towards glucose.The loading of Pt single atoms increases with doping of Co atoms that generate more anchoring sites for Pt SAs.The resulting Pt_(1)/Ni_(6)Co_(1)LDHs/NG exhibits low oxidative potential of 0.440 V with high sensitivity of 273.78μA·mM^(−1)·cm^(−2)toward glucose,which are 85 mV lower and 15 times higher than those of Ni(OH)_(2),respectively.Pt_(1)/Ni_(6)Co_(1)LDHs/NG also shows excellent selectivity and great stability during 5-week testing.Theoretical and experimental results show that the boosted performance of Pt_(1)/Ni_(6)Co_(1)LDHs/NG originates from its stronger binding energy with glucose and the synergistic effect of Pt SAs,Co doping,and NG.This work provides a general strategy of designing highly active SACs for extending their application in electrochemical sensing.

One-Step, Solvothermal Synthesis of Graphene-CdS and Graphene-ZnS Quantum Dot Nanocomposites and Their Interesting Photovoltaic Properties

The synthesis of graphene-semiconductor nanocomposites has attracted increasing attention due to their interesting optoelectronic properties.However the synthesis of such nanocomposites,with decorated particles well dispersed on graphene,is still a great challenge.This work reports a facile,one-step,solvothermal method for the synthesis of graphene-CdS and graphene-ZnS quantum dot nanocomposites directly from graphene oxide,with CdS and ZnS very well dispersed on the graphene nanosheets.Photoluminescence measurements showed that the integration of CdS and ZnS with graphene significantly decreases their photoluminescence.Transient photovoltage studies revealed that the graphene-CdS nanocomposite exhibits a very unexpected strong positive photovoltaic response,while separate samples of graphene and CdS quantum dots(QDs)of a similar size do not show any photovoltaic response.