Study On The Preparation And Control Of High Performance Of Iron-based Metal Phosphide Composite Catalysts For Water Splitting

The utilization of traditional fossil energy sources,which have been mined excessively,not only caused a series of environmental problems,but limited the fast development of the economy of the world today.Therefore,it is urgent for human to develop sustainable and pollution-free new energy in the world today.Hydrogen is considered to be the most promising new green energy in the 21st century,and the water electrolysis technology is considered to be the most promising large-scale hydrogen production technology for its high purity of product,convenient reaction condition and pollutant-free characteristic.Currently,the noble metal platinum-based materials and Ru₂O/Ir O₂ are used as commercial catalysts of cathode and anode,respectively.However,scarce reserves and unaffordable cost of noble metal-based restrict their large-scale application in the field of hydrogen production by water electrolysis technology.Although great progress has been made in the preparation of various catalysts for water electrolysis technology,there have been few reports on bifunctional catalysts that are both cost-effective and high-activity with great stability over a wide p H range.In this work,phosphorus-doped vertically aligned graphene arrays（P-VG）and iron-based transition metal phosphides（IMPs）were used to synthesize a series of IMP_S/P-VG composite catalysts for water electrolysis technology over a wide p H range.The performance of IMPs/P-VG were further improved by adjusting the morphology,structure and composition of the catalyst by adjusting the process conditions.The main research contents are as follows:In this paper,P-VG was successfully prepared by one-step directional freeze casting process.The effects of graphene concentration and other technological conditions on the porous morphology and internal vertical structure of P-VG were studied,and a method to prepare P-VG with large specific surface area and highly ordered was explored.Further,the composite catalyst was synthesized by anchoring single metal,double metal and three metal phosphide nanoparticles on P-VG substrates using a simple and mild chemical deposition method.The particle size,distribution and composition of phosphide nanoparticles in IMP_S/P-VG composite electrocatalyst were studied by photoelectron spectroscopy and other advanced characterization techniques,which facilitates the exploration of controllable preparation method of loaded polymetallic phosphides.Finally,influence of morphological structure and components on the HER and OER catalytic activity of IMPs/P-VG composite catalyst in a wide p H range was studied by using electrochemical test method.the relationship between the morphological structure and components of composite catalyst and catalytic performance was revealed through the comparative analysis of its performance,and then the catalytic reaction mechanism of high-performance FeCoNiP/P-VG was discussed.Furthermore,a series of composite electrocatalysts（IMPs/P-VG）with different cationic ratios were prepared by chemical deposition method.The surface composition,phase structure and valence state of phosphides were analyzed by some advanced characterization techniques.The results showed that the composite catalysts with different cationic ratios were successfully prepared.The HER and OER properties of the prepared materials in 1.0MKOH were compared by means of electrochemical test,and the influence of the cationic ratio in the phosphide on the electrocatalytic performance was analyzed.It is proved that the regulation of the cationic ratios has a positive effect on improving the intrinsic activity of phosphide.Besides,the catalytic mechanism for the composite catalyst with the best catalytic performance(Fe_0.5Co_1.5Ni_0.5P/P-VG)was studied by the quantitative analysis of the composition and phase structure of the catalysts after HER and OER stability tests.