Fig. 4: Impact of CO pressure (pco) on the oscillatory reaction over truncated Pd nanocube.
From: Periodic structural changes in Pd nanoparticles during oscillatory CO oxidation reaction
a Plots of the measured temperature, heater power, and b the corresponding amounts of the CO, O2, and CO2 gases during the CO oxidation reaction at 460 °C and \({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\approx 0.8\) and at 540 °C and \({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\approx 2.0\). The arrows in b correspond to the timepoints of the image series shown in c. c In situ TEM image series of a truncated nanocube showing a periodic restructuring corresponding to the oscillations during t = 0–1000 s at \({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\approx\) 0.8 (Supplementary Movie 3). At t = 1000–1400 s, when the partial pressure was increased to \({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\approx 2.0\), while maintaining the temperature at 460 °C, the corner of the nanocube became flat, and the activity dropped almost to 0. The oscillation resumed under this CO-rich condition (\({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\approx 2.0\)) when the temperature was increased to 540 °C at t \(\ge\) 1590 s (Supplementary Movie 4). d The ignition temperatures for the conversion reaction (\({T}_{{{{{{\rm{ig}}}}}}}\), orange circles) as a function of \({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\) and the corresponding dwell time of catalyst in low-activity (blue triangles) and high-activity (blue squares) states. e Ignition-induced temperature jump (\({{{{{{\rm{\delta }}}}}}T}_{{{{{{\rm{ig}}}}}}}\), orange circles) and concurrent drop in heater power (\({{{{{{\rm{\delta }}}}}}P}_{{{{{{\rm{ig}}}}}}}\), green circles), as indicated by arrows in Supplementary Fig. 20d as a function of the gas ratio (\({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\)). f The jump in temperature (\({{{{{\rm{\delta }}}}}}T\), orange circles) and concurrent drop in heater power (\({{{{{\rm{\delta }}}}}}P\), green circles) as a function of the gas ratio (\({p}_{{{{{{\rm{CO}}}}}}}/{p}_{{{{{{{\rm{O}}}}}}}_{2}}\)) at the onset of high-activity states of the oscillatory reaction, as described in a. The results shown in d–f are extracted from the measurements shown in Supplementary Fig. 20.
