Studies On Catalytic Performance Of Transition Metal Compounds In Water Oxidation And Nitrogen Reduction

Energy shortage and environmental problems have attracted much attention.Catalytic water splitting and reduction of nitrogen by electrochemistry have broad application.Transition metals,with abundant reserves,rich valence distribution and flexible coordination ability,are expected to become new catalysts to replace precious metals such as Ir,Pt and Rh.In this paper,Co3Se4-FeSe2 composites with excellent electrical conductivity were prepared to catalyze oxygen reaction in water splitting by hydrothermal selenification from different precursors and NiV-LDH with different NiV content ratios is obtained to regulate nitrogen reduction performance.The specific work is as follows:1.Three kinds of oxygen evolution catalysts:(1)Co3Se4-Fese2 composite selenides with good OER properties were successfully prepared by a simple one-step hydrothermal method using CoFe layered double hydroxide nanosheets(CoFe-LDH)as precursors.Co3Se4-FeSe2 catalyst can realize over-potential as low as 280 mV at 10 mA cm-2(close to RuO2),and Tafel slope is 51 mV·dec-1.This OER activity is also better than most reported selenide catalysts,and can last for 24 hours without significant decay.(2)Prussian-blue analog(PBA),a Prussian blue(PB)-like CoFe compound,was synthesized by a simple mixed crystallization method.The PBA synthesized by this method exhibited a nanocubic morphology with an average particle size of 250 nm.Se-PBA was obtained by hydrothermal method.The results showed that the products after selenization improved OER performance significantly.The overpotential is only 337 mV at 10 mA·cm-2,and the Tafel slope is 68 mV·dec-1.(3)Co3Se4 was synthesized from ZIF-67 by direct selenization and another is synthesized from Co3O4.The Overpotentials of the catalysts obtained by the two methods were 386 mV and 323 mV,respectively,at current density of 10 mA·cm-2.2.Nitrogen Fixation Catalyst:Three different proportions of NiV-LDH were synthesized by a simple one-step hydrothermal synthesis method.The results show that when Ni:V is 3:1,the performance of NiV-LDH is the best.After five long-term-cycle scans,NiV-LDH still maintained high stability.