Controlled Synthesis And Electrocatalytic Performance Of Transition Metal Based Bifunctional Nanomaterials

With the development of human technology and the improvement of people's living standard,human demand for energy is also increasing.Severe global energy crisis and environmental pollution issues have ignited great passion for developing sustainable energy conversion and storage devices.Therefore,it is urgent to develop and utilize new energy sources.Fuel cell,as a new type of energy conversion device,has become a top priority in new energy research due to its rapid start-up,high energy conversion efficiency and environmental friendliness.And the hydrogen production from electrolyzed water is also an important way to use hydrogen energy.Electrode catalysts play a crucial role in fuel cells and electrolytic water devices.Precious metal-based materials,such as Pt and Ir are still the most widely used electrode catalysts to date.However,many drawbacks exist with this process,such as the high price of Pt,and an insufficient efficiency and durability,which affect the widespread application.Therefore,it has become a research focus to study non-precious metal-based catalysts with low price,abundant reserves and excellent electrochemical catalytic activity and stability to replace precious metals.Based on the above research background,the transition metal-based bifunctional nanomaterials were synthesized in this thesis,and their electrocatalytic properties for oxygen reduction reaction?ORR?,oxygen evolution reaction?OER?and hydrogen evolution reaction?HER?were systematically studied.The specific work of this article is as follows:?1?The Co-Mn-rGO precursor was synthesized by hydrothermal method and calcined in ammonia gas atmosphere to obtain CoMn ON/N-rGO nanocatalytic material.With the introduction of Mn and GO,the specific surface area and the electron transfer rate of the catalyst is significantly improved.It is critical to enhance the catalytic performance and stability.By changing the doping ratio of Mn and GO,and optimizing the reaction synthesis conditions,the synthesized CoMnON/N-rGO nanocatalytic material exhibits excellent ORR catalytic performance,with a half-wave potential of 0.83 V and a limiting current density of 4.32 mA cm^-2.Meanwhile,it manifests a low overpotential of 350 mV at 10 mA cm^-2 for OER.?2?Ni-Fe-Mo precursors were synthesized by hydrothermal method,and Mo-Ni₃Fe/Ni₃FeN heterojunction nanocatalytic material were prepared after calcination in ammonia atmosphere.The influence of the phase structure,surface morphology,and valence of the catalyst on the catalytic performance of OER and HER was investigated.The developed Mo-Ni₃Fe/Ni₃FeN heterojunction nanocatalytic material exhibited excellent OER and HER catalytic properties,and the overpotentials at the current density of 10 mA cm^-2 were 240 mV and 234 mV,respectively.