Abstract: Provided is a catalytic activity recovery method of a manganese oxide catalyst, an air-cleaning device using the same, air-cleaning system including the air-cleaning device, and an operation method of air-cleaning device by using the manganese oxide catalyst. The catalytic activity recovery method of a manganese oxide catalyst includes recovering the initial activity of a manganese Ni oxide catalyst by heating a manganese oxide catalyst which has been used to decompose ozone and of which activity is thus reduced by 10% or more compared to the initial ozone decomposition efficiency thereof, at the temperature of 80° C. to 250° C.

Abstract: Provided are an air-cleaning device and method for reducing harmful gas including ethylene and harmful microorganisms, and an air-cleaning system including the air-cleaning device.

Abstract: Provided are a catalyst structure for ozone decomposition including a support containing a porous inorganic material, and an ?-MnO2 catalyst located on at least a portion of inner pores and a surface of the support, an air-cleaning method using the same, and an air-cleaning device and an air-cleaning system each including the catalyst structure for ozone decomposition.

Abstract: Provided are a catalyst structure for ozone decomposition including a support containing a porous inorganic material, and an ?-MnO2 catalyst located on at least a portion of inner pores and a surface of the support, an air-cleaning method using the same, and an air-cleaning device and an air-cleaning system each including the catalyst structure for ozone decomposition.