Analytics: Measurement of the gas phase composition at the reactor outlet was performed using Fourier-transform infrared spectroscopy (FTIR, MKS MultiGas 2030G, 2 cm optical pathlength) and mass spectrometry (MS, MKS Cirrus 3-XD). Both measurement techniques were operated at a sampling frequency of 1 Hz. FTIR was used to measure the molar fraction of NH3, while the data measured using the MS were used to analyze the molar fraction of Helium (He). The MS was further used for the qualitative measurement of the N2 and H2 step-responses.