Platinum supported on lanthana-modified hydroxyapatite samples for realistic WGS conditions: On the nature of the active species, kinetic aspects and the resistance to shut-down/start-up cycles

[Display omitted] •The promoting effect of La on the activity of Pt/HAP catalyst in WGS is evidenced.•La addition hinders the incorporation of Pt into the HAP framework and enhances the OSC.•The most active species consist of fine Pt particles exposed on both the HAP and lanthana surface.•The abundance of highly dispersed La species lowers the participation of the support vacant sites.•The resistance of the Pt/La(x)/HAP system is evidenced by withstanding severe shut-down/start-up conditions. The performance of a series of Pt/La(x)/HAP catalysts was investigated in the WGS reaction. It was found that the addition of La into the Pt/HAP catalyst enhances its OSC, hinders the incorporation of Pt species into the HAP framework, promotes its reducibility, decreases the Pt particle size and markedly improves its WGS activity. Moreover, the shut-down/start-up experiments demonstrate the high resistance of the investigated samples and the possibility of their use in mobile device applications. Kinetic data show that the reaction orders measured on Pt/La(4)/HAP agree with those corresponding to 1%Pt/Al2O3 catalyst. By contrast, the general tendency found on the rest of our samples, including the unpromoted one, resembles that shown by a Pt/CeO2 catalyst. Due to the presence of OH− vacant sites on our Ca-deficient HAP, it seems that it plays a role similar to that exhibited by the CeO2 reducible support.