Then, we extended the concept to the case of cobalt-catalyzed ammonia synthesis. The temperature dependence of N-binding energy on Co has been previously calculated by ab initio spin dynamics, and the temperature in the result has also been rescaled to the effective magnetization, as shown in Figure . Moreover, this system was predicted to exhibit optimal reactivity at an effective magnetization of 45%, rather than the totally demagnetized PM state. As a result, the 1 nm Co NP can theoretically achieve the Sabatier optimal of the ammonia synthesis at a temperature of ~910 K, which is about 300 K lower than the previously predicted value of its bulk counterpart. This suggests a possibility of approaching the volcano top of the transition-metal-based ammonia synthesis catalysts by the MCE at an applicable reaction condition.