Fabrication Of Nanoporous Electrodes And Its Electrocatalytic Performance On Oxygen Reduction Reaction And Nitrogen Reduction Reaction

With the crisis of fossil energy and the increasing environmental pollution caused by fossil energy,it is urgent to develop new and efficient clean energy materials.Fuel cell is a chemical device that can directly convert chemical energy into electrical energy.It is the fourth power generation technology after hydro,thermal and atomic power generation,and its product is only water and heat,which gradually becomes a kind of power generation technology,and becoming one of the most concerned energy conversion technologies.The activity and stability of catalyst in oxygen reduction reaction in cathode are very important in fuel cell system.Therefore,the development and preparation of highly efficient and stable low platinum oxygen reduction catalyst has attracted more and more attention of researchers.On the other hand,NH₃ is one of the most common industrial chemicals in contemporary society,and has been used in important fields such as agriculture.In industry,NH₃ is synthesized from N₂ and H₂ by Fe-based catalysts at high temperature and pressure.It consumes more than 1%of the world's energy supply and produces a large amount of CO₂derived from fossil fuels.Because of the high energy barrier of N-N bond splitting,N₂fixation is extremely difficult.In order to synthesize NH₃ under mild conditions and reduce its energy consumption,many efforts have been made to develop alternative ways to fix N₂ to NH₃.The electrochemical reduction synthesis of NH₃ from N₂ is a more new technology than the traditional synthesis of NH₃ under high temperature and pressure.It is also a carbon-free energy carrier,which can easily condense into liquid and overcome the storage limitation of H₂.Therefore,the search and synthesis of catalysts with high nitrogen electrochemical reduction activity has become a research hotspot.Nanoporous gold?NPG?prepared by dealloying method has higher specific surface area,electronic conductivity and stability than pure gold.It will be more meaningful to use these structural advantages to study electrocatalysis.In this paper,NPG was used as a substrate to deposit different metal atoms on the surface of NPG,and the catalysts with different atomic levels were prepared.The morphology and properties of the catalysts were investigated.The specific research contents are as follows:?1?NPG-Pt core-shell structure catalysts were prepared by underpotential deposition of copper on NPG surface and in situ substitution.The specific and mass activities of ORR before treatment were 0.9 V?vs.RHE?and 0.52 mA cm^-2,1.2 A mg_Pt^-1 respectively.The specific and mass activities of the catalysts after surface alloying were 0.89 mA cm^-2 and 1.57A mg_Pt^-1,respectively.The activity and mass activity were 1.7 and 1.3 times higher than those of the initial catalyst,respectively.This indicates that surface alloying can improve ORR activity.?2?A variety of catalysts were prepared by the same strategy and in situ replacement of Pd atoms,and their nitrogen reduction performance was tested.The yield of the products was measured and compared.It was found that Pd deposited on NPG surface could effectively increase the NH₃ yield of pure NPG due to its surface tension.The yield was 25.58 g h^-1 mg^-1,while the yield of NPG-Pd was 41.55 g h^-1 mg^-1,which was 1.62 times higher than that of NPG.At the same time,the NH₃ yield of Pd atom catalyst with different thickness deposited on NPG surface was compared,and it was found that the yield of single Pd atom layer was the highest.This discovery shows that the Pd element can increase the competitiveness of H₂precipitation reaction in NRR,but when Pd deposits a monolayer on NPG surface uniformly,it can effectively increase NH₃ yield because of its tensile.