Preparation Of Co/Mo Binary Metal Oxide Electrode And Its Application In Water Decomposition

Hydrogen(HER)and oxygen(OER)evolution reactions are the two half reactions in the electrolytic water splitting to produce H2,Pt-based composites are so far the most active catalysts for HER,while RuO2 and IrO2 are considered as the most efficient catalysts for OER.However,their large-scale applications are limited by high cost and poor natural abundance.Over the past decades,some transition metals are discovered to exhibit promising electrocatalytic activity toward water splitting,in which Co-based compound is one of the most representative mateirals.A good catalyst should be competitive not only in activity,but also in material cost,preparation method as well as the long-term stability.Herein,Co/Mo binary metal oxides are developed to be the bifunctional catalysts for water splitting.Free standing macroporous Co/Mo electrode,thin film and nanoparticles of this binary oxides are fabricated by etching/oxidation,electro-deposition,and chemical deposition methods,respectively.The crystalline structures,morphology,composition,as well as valance state were studied by introducing XRD,TGA,SEM,EDS and XPS techniques.Their OER/HER catalytic activity and long-term stability were measured by CV/LSV and chronoamperometry,respectively.The following conclusions were obtained:1)All the Co/Mo binary metal oxides prepared by different methods exhibit higher activity than single metal oxides(CoOx and MoOx).2)An etching method to fabricate free standing porous Co/Mo architecture as robust catalytic electrode for water splitting is firstly reported.The unique structure possesses large active sites,substantial oxygen vacancies and advantageous charge transport capability,making it a robust electrocatalyst toward OER and HER.It shows onset overpotential of 270 mV for OER,90 mV(in alkali)and 109 mV(in acid)for HER.The robust cathodic current density is presented as well.3)As for electro-deposition,the most efficient catalyst is prepared by constantly applying 10 ?A cm-2 anodic current for 700 s in a precursor with a atomic ratio of Mo:Co=20:1.It shows onset overpotential of 310 mV in 0.1 M KOH for OER and 190 mV in 1 M KOH for HER.A cathodic current density of 10 mA cm-2 is achieved at overpotential of 372 mV.4)As for chemical deposition,the most efficient catalyst is prepared from a precursor with the atomic ratio of Co:Mo=4:1,followed by annealing at a low-temperature of 300 ?.A low OER onset overpotential of 290 mV is achieved.The Co/Mo binary metal oxides electrod produced by etching/oxidation method exhibits the best architecture and the highest bi-functional catalytic activity toward water splitting.