Synthesis Of Porous Carbon-based Nanomaterials And Their Application Of Hydrogen Production

The excess greenhouse gas CO₂ released by the combustion of traditional fossil fuels is potentially harmful to global climate change,and finding clean carbon dioxide alternative energy is of great significance to the sustainable development of human society.As a non-carbon energy source,hydrogen has become the first choice for new energy with high combustion calorific value,non-polluting,non-toxic,colorless and odorless,easy storage and transportation,water is the only product after its combustion,and it will play an important role in the future clean energy carrier.In recent years,hydrous hydrazine,dimethylamineborane and formic acid have attracted the attention of many researchers because of their high hydrogen content and stable storage at room temperature.At present,efficient,low-cost,safe and selective hydrogen production from these materials is still very challenging.Therefore,the search for heterogeneous catalysts with good catalytic activity and stability is one of the research hotspots in this field.In this paper,three new porous carbon-based nanocatalytic materials were designed and developed,and the physical and chemical properties such as the composition and structural characteristics of these nanocatalytic materials were analyzed by characterization methods such as XRD,XPS,BET,TEM,HRTEM,and Raman spectroscopy,and their practical applications of catalytic hydrogen production were studied in detail.The specific research content includes the following three aspects:（1）Commercial Pt/C was alloyed with monometallic Ni by a deposition-precipitation method using Na BH₄as the reductant,and Ni Pt/C nanocomposites were successfully prepared by adjusting the composition ratio of Ni-Pt.Experimental results show that Ni₈Pt₁/C nanocomposites exhibit excellent catalytic activity in the dehydrogenation of hydrous hydrazine with the TOF of 2640.5 mol_（H2）·mol _Pt^-1·h^-1 at 50°C and 100%H₂ selectivity,the activation energy of the reaction was 39.8 k J/mol,while a single commercial Pt/C had almost no catalytic activity.More importantly,by adjusting the p H value in the reaction system,the"on-off"control reaction of Ni₈Pt₁/C nanocomposites catalyzed on-demand hydrogen production by hydrazine hydrate was developed and realized for the first time,which has a profound impact on the extensive rational utilization of hydrogen.（2）Using 3-aminophenol and formaldehyde as carbon source raw materials,under the action of weak alkali of ammonia,phenolic resin nanospheres of uniform size were synthesized by a pot method,and porous carbon nanospheres（CNS）with large specific surface area and rich O and N functional groups on the surface were obtained by high-temperature carbonization,and a series of CNS-supported Pt Ni bimetallic nanocatalysts(Pt_xNi_1-x/CNS)were synthesized by reducing Pt Ni nanoparticles in situ on the CNS surface under the action of sodium borohydride.It was found that the TOF of hydrolysis of dimethylaminoborane at 0.3 M Na OH and 30°C was 16,607 mol_（H2）·mol_cat^-1·h^-1 and the activation energy of the reaction was 31.1k J/mol.Interestingly,the large kinetic isotope effect verified that the breaking of a water O-H bond is the rate-controlling step of dimethylamineborane hydrolysis.（3）On the basis of the research of（2）,through the further optimization and improvement of the synthesis of porous carbon nanospheres（CNS）,porous carbon materials（CNSs）with larger specific surface area were synthesized,ultrafine Pd nanoparticles were reduced on the surface of CNSs with sodium borohydride as reducing agent,and a new and efficient monometallic Pd/CNSs nanocatalyst was successfully prepared,which was applied to selectively generate H₂ in the process of HCOOH dehydrogenation.The results show that the nanocatalyst Pd/CNSs-800 presented the highest catalytic activity for H2 generation from HCOOH,with the highest TOF of 2478 mol_（H2）·mol _Pd^-1·h^-1,CO₂ capture experiments,tandem reactions and GC results confirmed that Pd/CNSs-800 catalysts catalyzed HCOOH decomposition are 100%H₂ selectivity.In addition,the highly efficient and selective“on-off”switch for selective H₂ generation from HCOOH is successfully realized by p H adjustment.This opens up a new path for the development of economical and safe formic acid hydrogen production catalysts.