Application Of Iron-molybdenum-based Metal Oxysulfides In Electrocatalytic Nitrogen Reduction

Ammonia is one of the most important and basic chemicals in the world.It is not only an essential biomolecule,but also has important agricultural and industrial applications.In addition,due to its extremely high hydrogen content,ammonia is considered as a potential green energy storage carrier.Although nitrogen is very abundant in the atmosphere(78%),it is difficult to convert nitrogen to ammonia due to the extremely high disintegration energy of N?N(941 k J mol^-1).With the widespread application of the Haber-Bosch process,the problem of large-scale artificial ammonia production seems to have been solved.However,the traditional Haber-Bosch process requires demanding conditions,consumes a lot of energy,and causes air pollution.Therefore,it is urgent to develop a method to produce ammonia under environmental conditions.This can be achieved through a nitrogen reduction reaction(NRR),where nitrogen is electrochemically reduced to ammonia,which is a clean and sustainable solution.Among them,it is of great significance to explore the substitutes of non precious metals.Inspired by the natural biological nitrogen fixation with ferromolybdenum as the main active center of nitrogenase,researchers have studied various Mo based iron-based catalysts.Bimetallic oxides have been widely used in catalysis due to their unique structures.It is proved that FeMoO₄ nanorods are effective catalysts for nitrogen fixation by electric catalysis.In 0.1 M HCl electrolyte,the Faraday efficiency of the catalyst is10.2%at a voltage of-0.4 V and the NH₃ yield is 22.17?g h^-1 mg_cat.^-1 at a voltage of-0.45 V.Due to the poor chemical stability of FeMoO₄ under acidic conditions and the low ammonia yield or Faraday efficiency under neutral conditions,we sulfurized FeMoO₄ to imitate the components of nitrogenase in order to obtain higher ammonia yield and Faraday efficiency.The results show that under neutral conditions(0.1 M Na₂SO₄),the sulfurized FeMoO₄ can achieve the ammonia production rate of 31.93?g h^-1 mg_cat.^-1 and the higher Faraday efficiency(30.9%).The Faraday efficiency of this sulfured FeMoO₄catalyst is superior to most reported electrochemical NRR catalysts.