Phosphorus-doped iron-nitrogen-carbon catalyst with pentacoordinated single atom sites for efficient oxygen reduction

Single-atomic Fe-N4 is the well-acknowledged active site in iron-nitrogen-carbon(Fe-N-C)material for oxygen reduction reaction(ORR).The adjusting of the electronic distribution of Fe-N4 is promising for further enhancing the performance of the Fe-N-C catalyst.Herein,a phosphorus(P)-doped Fe-N-C catalyst with penta-coordinated single atom sites(FeNPC)is reported for efficient oxygen reduction.Fe K-edge X-ray absorption spectroscopy(XAS)verifies the coordination environment of single Fe atom,while density functional theory(DFT)calculations reveal that the penta-coordination and neighboring doped P atoms can simultaneously change the electronic distribution of Fe-N_(4)and its adsorption strength of key intermediates,reducing the reactionfree energy of the potential-limiting step.Electrochemical tests validate the remarkable intrinsic ORR activity of FeNPC in alkaline media(a half-wave potential(E_(1/2))of 0.904 V vs.reversible hydrogen electrode(RHE)and limited current density(JL)of 6.23 mA·cm^(−2))and an enhanced ORR performance in neutral(E_(1/2)=0.751 V,J_(L)=5.27 mA·cm^(−2))and acidic media(E_(1/2)=0.735 V,JL=5.82 mA·cm^(−2))with excellent stability,highlighting the benefits of optimizing the local environment of singleatomic Fe-N4.

In-situ exsolved ultrafine Ni nanoparticles from CeZrNiO_(2)solid solution for efficient photothermal catalytic CO_(2)reduction by CH4

CO_(2)reduction by CH4(CRM)to produce fuel is of great significance for solar energy storage and eliminating greenhouse gas.Herein,the catalyst of ultrafine Ni nanoparticles supported on CeZrNiO_(2)solid solution(Ni@CZNO)was synthesized by the sol-gel method.High yield of H_(2)and CO(58.0 and 69.8 mmol min^(-1)g^(-1))and excellent durability(50 h)were achieved by photothermal catalytic CRM merely under focused light irradiation.Structural characterization and DFT calculations reveal that CZNO has rich oxygen vacancies that can adsorb and activate CO_(2)to produce reactive oxygen species.Oxygen species are transferred to ultrafine Ni nanoparticles through the rich Ni-CZNO interface to accelerate carbon oxidation,thereby maintaining the excellent catalytic stability of the catalyst.Moreover,the experimental results reveal that light irradiation can not only enhance the photothermal catalytic CRM activity through photothermal conversion and molecular activation,but also improve the stability by increasing the concentration of oxygen vacancies and inhibiting CO disproportionation.