Preparation And Electrochemical Properties Of Single Mo Atoms And Al-doped NiO Nanosheets

Ammonia（NH₃）is the largest chemical product in the world,with an annual output of 150million tons.It can be used as agricultural fertilizer,chemical raw material and hydrogen-rich carrier.For more than 100 years,Haber-Bosch process has been used for large-scale production of NH₃.Haber-Bosch process is a process with high energy consumption and CO₂ emissions,so it is necessary to find more economical and effective production ways.Compared with traditional Haber-Bosch process,electrocatalytic N₂ reduction reaction（NRR）at room temperature and atmospheric pressure has many advantages:it can react at room temperature and atmospheric pressure;it can reduce costs;there are abundant resources of N₂ and H₂O in nature;and it can inhibit carbon emissions.Because it avoids the high temperature and high pressure of Haber-Bosch method,it has attracted much attention recently.In this paper,single Mo atoms anchored on N-doped porous carbon catalysts were prepared as low cost and high efficiency electrocatalytic NRR catalysts.At room temperature,the yield of NH₃ is as high as34.0±3.6μg h^-11 mg_cat.^-1 and the Faraday efficiency is 14.6±1.6%at-0.3 V（RHE）when 0.1M KOH is used as electrolyte solution,and these values are much higher than those reported previously for non-noble metal electrocatalysts.In addition,there was no obvious current drop during the electrocatalytic NRR of 50,000 seconds,which indicated the durability of the catalyst.This study provides a new idea for designing efficient and stable NRR catalysts,therefore,the practical application of NRR at room temperature and atmospheric pressure is promoted.Inadequate storage of fossil fuels and global warming are major energy issues,which prompt people to concentrate on expanding and developing renewable energy technologies.The rapid growth of renewable energy sources such as solar energy and wind energy has forced the development of a new generation of energy storage systems.Current battery systems face difficulties in peak power,however supercapacitors are the most promising energy storage devices in this area.The design of electrode materials is the key to the development of asymmetric supercapacitors with high electrochemical performance and stability.In this paper,Al doped NiO nanosheet arrays were grown on the surface of nickel foam（NFs）have synthesized.Compared with undoped NiO nanoarrays,Al-doped NiO nanosheets have higher capacitance.When the current density is 1 A g^-1,the specific capacitance is 2253±105 F g^-1.More importantly,the nanosheet shows excellent rate performanceand indicats its high cycle stability.The capacitance performance of the material is mainly attributed to its large electrochemical active area and strong conductivity.In addition,asymmetric supercapacitors（ASCs）based on Al-doped NiO nanosheet arrays and N-doped multi-walled carbon nanotubes（MWCNTs）have achieved energy density of 215±15 Wh kg^-1 and power density of 21.6 kW kg^-1.This work is helpful to develop new high performance pseudocapacitive electrode materials.