Comment on "Designed oxygen carriers from macroporous LaFeO3 supported CeO2 for chemical-looping reforming of methane", by Zheng et al. [Appl. Catal. B: Environ., 202 (2017) 51-63. doi: 10.1016/j.apcatb.2016.08.024]

Here, I shall comment on the authors' interpretation of their XPS spectra, specifically Ce3d, Fe2p, and O1s spectra of x%CeO2/LaFeO3 (x = 5, 10, 20 wt%) samples as a function of x and of CLRM cycling. While I find that Zheng et al. achieve and document some important progress in the catalytic performance of these materials [1], I believe that a good part of their interpretation of XPS results is unwarranted.