The Surface/Interface Structural Regulation Of Cobalt-Based Low-Dimensional Composite Nanomaterials And The Study On Its Photo/Electro Catalytic Enhancement Effect

One of the most effective technologies to replace energy in the future is to use photocatalysis and electrocatalysis technology to convert solar energy and chemical energy into electrical energy,and the design and synthesis of high-efficiency catalysts is one of the decisive technologies.It is found that most transition metal?such as Co,Ni,Fe,Cu?composites have simple and mature synthesis,and have incomparable advantages in achieving selective activation,so they are good catalysts and have important applications in both catalysis and electrocatalysis.Among them,cobalt-based nanocatalysts have shown excellent catalytic performance in photo/electrocatalysis.In this paper,three types of cobalt-based nanomaterials were designed and the electrocatalytic and photocatalytic performance of these cobalt-based materialsis were enhanced by adjusting the surface/interface structure.1.A simple solvothermal method was used to synthesize a PtCo alloy@cobalt benzoate/graphene?PtCo@Co-BA/Gr?composite catalyst with a multi-dimensional structure of 0D/1D/2D.Among them,cobalt?II?benzoate as a key carrier had suitable internal channels to support Pt nanoparticles,which could be formed in one-dimensional channels by in-situ reduction to form a PtCo alloy,and the hydroxyl group on the outer surface of cobalt?II?benzoate resulted in a strong interaction between cobalt benzoate and graphene.Compared with commercial Pt/C catalyst,the prepared PtCo@Co-BA/Gr composite catalyst showed a larger electrochemically active surface area,and exhibited higher activity and durability in the electrocatalytic oxidation of methanol,ethanol,and ethylene glycol in acidic medium.2.Cobalt-based nanomaterials have been used in photocatalysis for a long time due to their narrow bandgap width and high utilization rate of sunlight.In this section,the ZnCdS/NiCo-LDH composite catalyst was synthesized by hydrothermal method.By adjusting the Zn/Co ratio,three composites with different structures were obtained,including Z-type heterojunction,semi-enclosed and core-shell structure.The performance of hydrogen production by splitting water under visible light???420nm?was compared,using triethanolamine as a sacrificial agent.It was found that the ZnCdS/NiCo-LDH composite with semi-enclosed structure showed the optimal activity and superior stability for water splitting by visible light.The hydrogen production rate was 2.8 mmolg^-1h^-1,which was 16 times and 8 times higher than pure ZnCdS and NiCo-LDH respectively.Meanwhile,the mechanism of the performance enhancement of as-obtained ZnCdS/NiCo-LDH catalyst with semi-enclosed structure was explored by energy band calculation,photoelectric performance analysis and free radical measurement.3.In order to further improve the stability and catalytic activity of the above ZnCdS/NiCo-LDH catalyst with semi-enclosed structure,the precious metals?Pt,Au,Ag?were loaded on above ZnCdS/NiCo-LDH catalyst to obtain semi-enclosed Z-structure catalyst,such as Pt/ZnCdS/NiCo-LDH,Au/ZnCdS/NiCo-LDH,Ag/ZnCdS/NiCo-LDH.By altering the content of noble metals,it was found that Au?1wt.%?/ZnCdS/NiCo-LDH exhibited the optimal activity and stability to produce hydrogen by splitting water under visible light.The hydrogen production rate was 4.9mmolg^-1h^-1,nearly 2 times higher than that of ZnCdS/NiCo-LDH catalyst,and the hydrogen production rate reached 98.7%after 10 cycles.Through the investigation of catalyst structure and photoelectric performance,it was found that a perfect semi-enclosed Z-type structure was formed when Au was loaded between the interface of ZnCdS and NiCo-LDH,which was the critial to improve its catalytic performance.