Regulating the valence and size of the active center of Co/AlO catalyst improved the performance and selectivity of NH-SCO.

To improve the activity of Co/AlO catalysts in selective catalytic oxidation of ammonia (NH-SCO), valence state and size of active centers of AlO-supported Co catalysts were adjusted by conducting H reduction pretreatment. The NH-SCO activity of the adjusted 2Co/AlO catalyst was substantially improved, outperforming other catalysts with higher Co-loading. Fresh Co/AlO catalysts exhibited multitemperature reduction processes, enabling the control of the valence state of the Co-active centers by adjusting the reduction temperature. Changes in the state of the Co-active centers also led to differences in redox capacity of the catalysts, resulting in different reaction mechanisms for NH-SCO. However, in situ diffuse reflectance infrared Fourier transform spectra revealed that an excessive O activation capacity caused overoxidation of NH to NO and NO. The NH-SCO activity of the 2Co/AlO catalyst with low redox capacity was successfully increased while controlling and optimizing the N selectivity by modulating the active centers via H pretreatment, which is a universal method used for enhancing the redox properties of catalysts. Thus, this method has great potential for application in the design of inexpensive and highly active catalysts.