Research On Hydrogen Production Characteristics Of Formic Acid Driven By Photothermal Based On Porous Absorber

The energy crisis caused by fossil fuel consumption is becoming increasingly serious and the pollution to the environment is becoming more and more serious.Therefore,it is inevitable to develop and utilize new renewable energy.Hydrogen energy,as an ideal clean energy,has only water as combustion product,which is considered one of the best new energy sources in the 21st century,and it is expected to replace fossil fuels,which has attracted the extensive research interest of researchers.In the development of hydrogen energy,because of its special properties such as inflammable and explosive,realize the safe and efficient storage and transportation of hydrogen has become the barrier to the development of hydrogen energy scale.At present,hydrogen storage has been developed in a variety of ways.Compared with other methods,chemical storage has the advantages of convenience safety and stability.As the raw material of chemical hydrogen storage,formic acid（HCOOH,FA）has 4.4wt%hydrogen content,liquid at room temperature,has the characteristics of renewable and non-toxic.It is considered as a good chemical hydrogen storage material.At present,the system of catalytic decomposition is mainly liquid-solid heterogeneous reaction in the dehydrogenation of formic acid,which is to put catalyst directly into the reaction solution.Although a series of progress has been made in the research of catalyst at present,a series of energy consuming operations such as stirring and heating are still needed in the reaction system.The concentration limit requires adding catalyst to inhibit the ionization of formic acid and promote dehydrogenation of formic acid,thus limiting the scale application.Therefore,it is the key to develop a new reaction system and realize the high efficiency dehydrogenation of formic acid in the basis of zero energy consumption.In view of this,this paper focuses on the following research:（1）A new type of dehydrogenation system of formic acid was studied,and the energy was supplied by solar energy.The Pd nanoparticles were loaded on the photothermal substrate,which is reduced graphene oxide aerogels（rGO）.Pd/rGO aerogels were used for photothermal conversion and its optical absorption properties were studied.The results showed that aerogels showed broad spectrum absorption,and Pd nanoparticles showed dual functions.The plasmon resonance enhanced the optical absorption,and finally the overall absorbance of Pd/rGO aerogels reached over 90%.In addition,another role of Pd nanoparticles is to provide catalyst for dehydrogenation of formic acid.At the same time,the extensive spectrum absorption and photothermal conversion ability of the reduced graphene oxide aerogels are used to provide heat for the reaction and improve the activity of the catalyst.（2）The non-contact thermal utilization method was applied to dehydrogenation of formic acid,and the thermal efficiency of different heat utilization methods was compared.Among them,reduced graphene oxide aerogels have high photothermal properties.After achieving good photothermal conversion performance,non-contact applications restrict heat to aerogels,and heat isolation is achieved by using gas gaps between the aerogels and the liquid surface.At the same time,thermal radiations are used to exchange heat with the lower layer solution,and the infrared photons radiated downward are penetrated at micron level.The results show that the solution is absorbed by the lower formic acid solution,which can achieve high-efficiency spectral absorption,excellent photothermal conversion efficiency and multi-stage gradient utilization of heat.（3）A new gas-solid heterogeneous catalytic method for the dehydrogenation of formic acid was studied.The thermal effect of localized heat in the heat was achieved by the gas gap in the middle.Meanwhile,the heat exchange between the solution and the lower solution was realized by thermal radiation,and the formic acid solution was converted from the liquid phase to the gas phase.The diffusion of formic acid was used to transport the reactants to the graphene aerogel.The porous structure of graphene aerogels provides a place for reaction.Pd nanoparticles provide catalysis,and eventually formic acid catalyzes gas-solid heterogeneous catalysis.Through the above research,the finally results show that the use of pure formic acid,in the use of 1000 W/m²of irradiance.The continuous dehydrogenation of TOF=4799.8 h^-1 was realized in 120 h,and 100%hydrogen selectivity was realized.Meanwhile,the conversion rate of formic acid was maintained at about 80%,and the high efficiency dehydrogenation was realized under zero energy consumption.It was proved that the conversion of solar energy to hydrogen energy formed a collaborative bond,which provided a new idea for the application of dehydrogenation of formic acid.