Influencing mechanism of alkali metals on the adsorption property of NH3, NO, O2 and dehydrogenation reaction of NH3 on the β-MnO2 (1 1 0) surface: A DFT + U study

•The activity of β-MnO2 (110) surface is significantly reduced by K or Na mainly through inhibiting the adsorption of NH3.•K or Na can enhance the deNOx activity of β-MnO2 (110) surface in some situations by enhancing the adsorption of NO.•The reasons for K or Na inhibiting the adsorption of NH3 or promoting the adsorption of NO was discussed.•K or Na severely inhibits the process of NH3 dehydrogenation while promotes the production of H2O.