Fig. 2: Catalytic performances.

a NH3 synthesis rate for Co–N–C, Co/C, and N–C under 1 MPa and b NH3 synthesis rate of selected catalysts at 350 °C under 1 MPa (The data points and error bars represent the average and standard deviation based on multiple measurements on the same catalyst at different times over different batches of samples). c Time course of NH3 synthesis rate at 350 °C over Co–N–C and d Arrhenius plots.