Study On Electrical Synthesis Of Ammonia From Nitric Oxide On Membrane Electrode

Ammonia is the second largest chemical product in the world.The traditional Haber process for ammonia synthesis suffers from huge energy consumption and serious environmental pollution,and there is an urgent need to develop new ways of ammonia synthesis.Electrochemical ammonia synthesis has mild conditions and zero CO₂ emissions,providing a potential greener alternative for ammonia production.Electrochemical ammonia synthesis using atmospheric pollutant nitric oxide as raw material not only reduces energy consumption for ammonia synthesis,but also reduces nitric oxide pollution emission,which has great potential for pollution reduction and energy saving.To address the problems of low conversion and difficult product separation in the electrochemical synthesis of ammonia from nitric oxide,this paper proposes the idea of electrochemical reduction of nitric oxide and in situ separation of ammonia on membrane electrodes,synthesizes two catalyst-gas diffusion electrodes of gold/polytetrafluoroethylene（Au/PTFE）and copper/porous carbon（Cu@C/CFP）,and constructs a three-phase catalytic interface of“liquid phase-catalyst-gas phase”to achieve efficient reduction of nitric oxide to produce ammonia and in situ separation of ammonia,and initially reveals the mechanism of nitric oxide conversion and ammonia separation,the specific conclusions are as follows.We designed a Au/PTFE membrane electrode with both nitric oxide catalytic ability and ammonia separation performance,and achieved 60.5%ammonia Faraday efficiency and 37.5%ammonia separation rate.The Au/PDA@PTFE membrane electrode was synthesized by polymerization and oxidation on PTFE surface and in situ growth of polydopamine to achieve improved electrolytic performance,and the Faraday efficiency and separation rate were increased by 7%and 13.1%,respectively,compared with the original Au/PTFE electrode.Au-based membrane electrode realized the in-situ separation of ammonia and ammonia produced by electric reduction of nitric oxide,and verified the effectiveness of membrane electrode preparation and separation of ammonia.But there are still problems of limited catalytic efficiency,low ammonia separation rate and small current density,which need further research to solve.To further improve the selectivity,current density and ammonia separation performance of membrane electrode catalyzed ammonia production from nitric oxide,Cu,a metal with higher selectivity for the reduction of nitric oxide to ammonia,was selected as the catalyst.The synthesis of Cu@C/CFP electrode by the polydopamine encapsulation-carbonation method achieved 84.1%ammonia faraday efficiency,62%ammonia separation rate and 11.5 m A/cm² ammonia current density,realizing efficient ammonia production and separation at the membrane electrode.The synthesis of carbon layer-wrapped Cu nanoparticles by polydopamine wrapping-carbonation preserves the high catalytic activity of singlet Cu and enhances the chemical stability,and the high current density from the high activity creates conditions for the local high p H environment on the surface of Cu@C/CFP electrode,and the NH₃separation rate on the electrode after wrapping is increased to 62%from30.6%before wrapping.