BACKGROUND In this study, manganese dioxide (MnO2) was formed in situ on the surface of ACF(N) (nitric acid modified activated carbon fibres) by a one-step redox method for the selective catalytic reduction (SCR) of nitric oxides (NOx) with ammonia (NH3) at low temperature. Meanwhile, the water and sulfur dioxide (H2O and SO2) deactivation mechanism were investigated. RESULTS Each acid, including hydrochloric, nitric and acetic (HCl, HNO3 and CH3COOH), released H+ in solution at different rates, which lead to distinct pH environments. As the driving force, it has an effect on the redox reaction, resulting in the different MnO2 amount and performance of the MnO2/ACF(N) catalysts. The MnO2/ACF(N) (CH3COOH) catalyst exhibited good NH3-SCR activity, water resistance and sulfur resistance. CONCLUSION The MnO2/ACF(N) (CH3COOH) catalyst showed 3D growth and uniform distribution of MnO2 sheets on the surface of the support, which resulted in a larger specific surface area and better redox properties. The CH3COOH can gradually decompose H+ so that H+ is given priority to internal diffusion. The redox reaction preferentially took place in the interior, thereby promoting the formation of more MnO2, which is beneficial to the NH3-SCR reaction. (c) 2019 Society of Chemical Industry