Understanding Co‐Mo Catalyzed Ammonia Decomposition: Influence of Calcination Atmosphere and Identification of Active Phase

To elucidate the effect of textural and chemical properties of catalysts and to discriminate the active phase are fundamental issues in heterogeneous catalysis, but they are often complicated by the nature of support adding a new dimension. In this work, metal amine metallate (Co(en) 3 MoO 4 ) precursor was directly treated by calcination and prenitridation to understand these two issues in Co‐Mo catalyzed ammonia decomposition. The calcination atmosphere (i.e., Ar and Air) is found to remarkably affect the textural and chemical properties of catalysts, and air atmosphere is favorable for higher stable reactivity despite incomplete nitridation of the catalyst. Further prenitridation of the sample from the calcination of Co(en) 3 MoO 4 under air gives rise to higher catalytic activity, and Co 3 Mo 3 N is suggested as the dominant active phase of Co‐Mo catalysts. The insights revealed here shed new light on the design of Co‐Mo catalysts for ammonia decomposition.