Preparation Of Non-noble Metal-based Nanomaterials And Their Application In Electrocatalysis

Environmental and energy issues are becoming more and more serious with the development of society and economy,therefore the development of environmentally friendly clean energy is imminent.Hydrogen energy has been a research hotspot of clean energy in recent years,not only has a high combustion value,but also is clean and pollution-free.Proton exchange membrane fuel cell（PEMFC）has an important application prospect as an efficient hydrogen energy utilization technology.To date,precious metal Pt-based nanomaterials are the most commonly used catalysts towards oxygen reduction reaction（ORR）for PEMFCs.However,under long-term operating conditions,the practical application of Pt-based electrodes（typically Pt/C）in PEMFCs is hampered by certain factors.In particular,the corrosion of the carbon support exacerbates the sintering,agglomeration,shedding and loss of Pt,which seriously affects the catalytic efficiency and life of the Pt-based catalyst.Therefore,exploring new high-performance support materials is a practical and important way to improve the catalytic performance of Pt.Electrochemical water splitting technology offers a promising route for scalable and sustainable hydrogen production,which requires high-performance and stability oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）bifunctional electrocatalysts to lower the overpotential and reduce the energy consumption.Hydrogen energy has been a research hotspot in recent years due to its high calorific value,convenient preparation and no pollution.The noble metals RuO₂ and Pt/C have high oxygen evolution and hydrogen evolution reactivity,but due to their high cost and scarcity,they have seriously hindered the wide application of noble metal-based catalysts in hydrogen production from electrolysis of water.Therefore,in the development of electrolyzed water technology,it is particularly important to effectively reduce the cost of the catalyst and develop a non-precious metal catalyst with high activity and high stability.（1）In this work,atomic layer deposition was facilely adopted to fabricate TiN nanoparticles onto carbon nanotubes（CNTs）,and then the prepared TiN/CNTs hybrid was used as a support of Pt catalyst.The resulting TiN/CNTs supported Pt nanoparticles（Pt@TiN/CNTs）nanocomposite showed remarkable catalytic performance towards the oxygen reduction reaction as compared to commercial Pt/C.Only a slight performance loss can be observed after 5000 potential cycles.The experimental results show that the prepared Pt@TiN/CNTs catalyst possesses higher catalytic activity and long-term stability towards ORR,which should be due to the high conductivity and high stability of TiN,as well as the favorable Pt-TiN interaction.The developed transition metal nitride coated CNTs composites as Pt-based catalyst support have potential application prospects in fuel cells.（2）Herein,we demonstrate that ZnCo₂S₄ nanosheet array in situ grown on 3D nickel foam（ZnCo₂S₄/NF）acts as an excellent candidate catalyst for electrochemical splitting of water with high efficiency and durable by hydrothemal process.High OER performance and HER properties achieved by flower-like nanoflake array structure.The resulting ZnCo₂S₄/NF achieves a much low overpotential of 301 mV at 50 mA cm^-2 for OER and185 mV at 10 mA cm^-2 for HER in alkaline solution.The two-electrode configuration needs cell voltage of 1.66 V to reach current density of 10 mA cm^-2.This research provides us an attractive highly efficient and durable catalyst electrode for overall water splitting application.