“…The Ce 3dp5/2 spectra can be divided into four characteristic peaks at 882.5 eV (Ce 4+ ), 885.8 eV (Ce 3+ ), 888.8 eV (Ce 3+ ), and 898.3 eV (Ce 2+ ), respectively, while the Ce3d3/2 spectra can also be divided into four characteristic peaks at 901.4 eV (Ce 4+ ), 903.8 eV (Ce 3+ ), 907.3 eV (Ce 4+ ), and 916.8 eV (Ce 4+ ), respectively. The coexistence of Ce 2+ , Ce 3+ , and Ce 4+ can create a charge imbalance, vacancies, and unsaturated chemical bonds on the catalyst's surface [52] and, as a result, can increase the SCR activity of the catalyst [53]. Among these cerium oxides, CeO 2 has been proven as the most effective oxide type of cerium for SCR activity, which was the main valence state in the 9%Ce(0.3)-Mn/TiO 2 -0.8%GO catalyst.…”