Fig. 1: Experimental set-up and relative turnover-frequency measurements.
From: Operando probing of the surface chemistry during the Haber–Bosch process
a, The sample faces a set of apertures that deliver the reaction gas while simultaneously gathering products and emitted electrons. The grazing incidence X-rays enter from the left, producing photoelectrons. The mix of gas and electrons is separated by an electrostatic lens and analysed in an electron analyser and a mass spectrometer. The inset shows XPS spectra of the chemical state of N at 200 mbar over the Fe(110) surface with a 1:3 N2:H2 gas ratio. b, Mass spectrometer readout of masses 15 and 16 corresponding to NH3 production as the gas ratio changes from 150 mbar pure N2 (blue region showing flow) to 300 mbar 1:1 N2:H2 (green region showing flow) over Ru at 673 K. Note that the flows of the gases are shown as the filled blocks plotted on the left axis. c, The enhanced mass spectrometer signals were time averaged during the interval of the 1:1 N2:H2 mixture to estimate the relative chemical reactivity. a.u., arbitrary units.
