As the flow rate decreases, the adsorbed species derived from produced ammonia increases. The ammoniaderived adsorbed species NHx (x = 0, 1, 2, 3) are likely to adsorb on the catalyst surface, resulting in higher 𝜃 NH x coverage. The increase in 𝜃 𝑁𝐻 𝑥 means that the equilibrium of reaction steps other than RDS is relatively biased toward the product system, and reactions that reduce 𝜃 𝑁𝐻 𝑥 , i.e., reverse reactions, are more likely to occur.