Preparation of nanostructured mesoporous Ni Co_2O_4 and its electrocatalytic activities for water oxidation

Nanostructured mesoporous Ni Co2O4,Co3O4 and Ni O spinel oxides were prepared through the hydroxide coprecipitation method using EG（ethylene glycol） as solvent without any template.The Ni Co2O4 powders were analyzed by TGA,XRD,N2adsorption-desorption,SEM and EDS.And the electrocatalytic properties of Ni Co2O4/Ti,Co3O4/Ti and Ni O/Ti electrodes for oxygen evolution in 0.1 mol/L KOH（p H = 13）were tested by cyclic voltammetry,Tafel curves and electrolysis.The result shows that Ni Co2O4/Ti electrode has higher electrocatalytic activity in oxygen evolution reaction than Co3O4/Ti and NiO/Ti electrodes.Ni Co2O4/Ti electrode prepared at 350°C has the highest apparent current density and the highest true current density.The Tafel slope of Ni Co2O4/Ti electrode prepared at 350°C is 68.49 m V/dec.

Ag nanoparticles anchored on MIL-100/nickel foam nanosheets as an electrocatalyst for efficient oxygen evolution reaction performance

Metal-organic frameworks(MOFs)exhibit excellent application potential in the field of electrocatalysis.In this study,we first prepare MIL-100 nanosheets on nickel foam(MIL-100/NF)and then successfully anchor Ag nanoparticles(NPs)on the nanosheets(Ag@MIL-100/NF)for oxygen evolution reaction(OER)catalysis.This strategy dramatically improves the conductivity of MIL-100 and the Ag NPs are uniformly dispersed on the nanosheets.The Ag@MIL-100/NF catalyst has excellent electrocatalytic performance and long-term corrosion resistance,with a low overpotential of 207 mV and a long-term stability of at least 100 h at a current density of 50 mA·cm^(-2).The experimental results demonstrate that this high OER catalytic performance is due to the improved charge transfer after loading Ag NPs,the combination of nanosheets and highly dispersed Ag NPs that expose more active sites and the adjusted chemical valence states of Fe and Ni in MIL-100.This work provides a surface decoration approach for the preparation of excellent catalysts directly used in the OER.

Strengthen metal-oxygen covalency of CoFe-layered double hydroxide for efficient mild oxygen evolution

Oxygen evolution reaction(OER)is crucial for hydrogen production as well as other energy storage technologies.CoFe-layered double hydroxide(CoFe-OH)has been widely considered as one of the most efficient electrocatalysts for OER in basic aqueous solution.However,it still suffers from low activity in neutral electrolyte.This paper describes partially oxidized CoFe-OH(PO-CoFe-OH)with enhanced covalency of M-O bonds and displays enhanced OER performance under mild condition.Mechanism studies reveal the suitably enhanced M-O covalency in PO-CoFe-OH shifts the OER mechanism to lattice oxygen oxidation mechanism and also promotes the rate-limiting deprotonation,providing superior OER performance.It just requires the overpotentials of 186 and 365 mV to drive the current density densities of 1 and 10 mA·cm^(-2) in 0.1 M KHCO_(3) aqueous solution(pH=8.3),respectively.It provides a new process for rational design of efficient catalysts for water oxidation in mild conditions.