Construction,Photoelectrocatalytic Oxidation Properties Of Transition Metal Based LDHs Materials And Application In Fuel Cells

At present,it is a top priority to explore green energy technologies to replace fossil energy in sustainable development.Water splitting,as a powerful technology for converting renewable energy into hydrogen energy,is difficult to be applied on a large scale due to the slow kinetics of oxygen evolution reaction（OER）.Secondly,biomass oxidation instead of OER is very advantageous in thermodynamics,and biomass energy has a large reserve in nature,can be electrocatalytic conversion to chemicals,but biomass electrocatalytic oxidation is also limited by slow kinetics,which greatly affects the discharge performance of fuel cells.Therefore,solar energy,as an inexhaustible source of energy,is used to promote the kinetic development of fuel cell anode reaction.At the same time,the development of high efficiency and low cost non-noble metal anode catalyst materials is very important to reduce overpotential and improve hydrogen production efficiency.In this paper,the photocatalytic fuel cell anode catalyst as the research object,based on the alkaline and Thermal decomposition of layered double hydroxides（LDHs）materials,transition metal-based LDHs materials were designed and constructed,which were used for anodic oxidation reaction of fuel cell.On this basis,the application of fuel cell is further explored.The main research is as follows:1.Inspired by the structure of LDHs and the wide application of LDHs in photocatalytic and electrocatalytic processes,the photoelectric synergytowards catalyzing OER was proposed.In order to obtain excellent photoassisted electrocatalytic OER（OER）performance,an ultrathin flower-shaped LDHs nanosheet rich with oxygen vacancy was developed by using the acidysis property of LDHs.5:1 E-NiFe-Nss exhibited excellent catalytic kinetics and fast charge transfer,while effectively capturing visible light.The overpotential(267mV@10mA cm^-2)under AM 1.5 irradiation was reduced by 29mV in1.0MKOH solution,the photocurrent of 5:1E-NiFe-Nss was 6 times that of5:1NiFe-Nss at 0.4V（vs SCE）.The oxygen vacancies created by acid etching can absorb more wavelengths of light,enhance its intrinsic activity,and improve the electronic structure to provide more active sites.2.High entropy oxides（HEOs）are the most potential catalytic materials due to their unique physicochemical properties such as cocktail effect and high entropy effect.However,the catalysts prepared by traditional high-temperature synthesis techniques with poor catalytic activity due to defects such as low specific surface area and few exposed active sites.In this work,inspired by the thermally stable transformation of LDHs into metal oxides（MMOs）,amorphous high-entropy LDHs（HE-LDHs）were used as precursors to synthesize high-entropy oxide nanosheets（HELOs）by etching and low-temperature roasting strategies,and the HELOs were applied to photoelectrocatalytic oxidation of biomass models（methanol and glucose）.Owing to the ultrathin nanosheet structure,abundant oxygen vacancies and high specific surface area,the NiCOFeCuCr-HELOs-2 could effectively capture visible light,and had higher activity,lower initial potential and faster charge transfer kinetics for methanol and glucose oxidation,which is better than HEOs prepared at high temperature.In addition,biomass oxidation instead of OER is also more efficient in thermodynamics,and can improve the efficiency of hydrogen production.Glucose fuel cells were assembled with HELOs-2 as photoanode,and the open-circuit voltage,short-circuit current,and maximum power density were about 1.7 times,1.57 times,and 2 times higher than those in the dark,respectively.This method provides a new idea for the development of simple and efficient nanostructured HEOs.