Engineering practice and economic analysis of ozone oxidation wet denitrification technology

SO_(2)and NO emitted from coal-fired power plants have caused serious air pollution in China.In this study,a test system for NO oxidation using O_(3)is established.The basic characteristics of NO oxidation and products forms are studied.A separate test system for the combined removal of SO_(2)and NO_(x)is also established,and the absorption characteristics of NO_(x)are studied.The characteristics of NO oxidation and NO_(x)absorption were verified in a 35 t·h^(-1)industrial boiler wet combined desulfurization and denitrification project.The operating economy of ozone oxidation wet denitrification technology is analyzed.The results show that O_(3)has a high rate and strong selectivity for NO oxidation.When O_(3)is insufficient,the primary oxidation product is NO_(2).When O_(3)is present in excess,NO_(2)continues to get oxidized to N_(2)O_(5)or NO_(3).The removal efficiency of NO_(2)in alkaline absorption system is low(only about 15%).NOx removal efficiency can be improved by oxidizing NO_(x)to N_(2)O_(5)or NO_(3)by increasing ozone ratio.When the molar ratio of O_(3)/NO is 1.77,the NOx removal efficiency reaches 90.3%,while the operating cost of removing NO_(x)per kilogram is 6.06 USD(NO_(2)).

Design and operando/in situ characterization of precious-metal-free electrocatalysts for alkaline water splitting

Electrochemical water splitting has attracted considerable attention for the production of hydrogen fuel by using renewable energy resources.However,the sluggish reaction kinetics make it essential to explore precious-metal-free electrocatalysts with superior activity and long-term stability.Tremendous efforts have been made in exploring electrocatalysts to reduce the energy barriers and improve catalytic efficiency.This review summarizes different categories of precious-metal-free electrocatalysts developed in the past 5 years for alkaline water splitting.The design strategies for optimizing the electronic and geometric structures of electrocatalysts with enhanced catalytic performance are discussed,including composition modulation,defect engineering,and structural engineering.Particularly,the advancement of operando/in situ characterization techniques toward the understanding of structural evolution,reaction intermediates,and active sites during the water splitting process are summarized.Finally,current challenges and future perspectives toward achieving efficient catalyst systems for industrial applications are proposed.This review will provide insights and strategies to the design of precious-metalfree electrocatalysts and inspire future research in alkaline water splitting.