Surface chemical compositions of as-prepared Co–Mn composite oxides.

Samples	Co3+	Co2+	Co3+/Co2+	Mn4+	Mn3+	Mn2+	OI	OII	OIII
Co3O4	0.588	0.412	1.43	—	—	—	0.547	0.347	0.106
Co2MnO4	0.663	0.337	1.96	0.293	0.413	0.294	0.471	0.428	0.155
Co1.5Mn1.5O4	0.717	0.283	2.54	0.276	0.471	0.253	0.435	0.464	0.101
CoMn2O4	0.622	0.378	1.65	0.262	0.456	0.282	0.504	0.390	0.106
Mn3O4	—	—	—	0.263	0.368	0.367	0.535	0.355	0.11