Designing a new generation of catalysts: Water gas shift reaction example

•Natural formation of interfacial nano mixed-oxides.•Supported ceria nanoparticles reduction by interfacial mixed-oxide formation.•Catalyst activation by natural reduction of supported ceria.•Key concepts for designing new oxide/metal catalysts.•Deep review on key factors for a good water gas shift reaction catalyst. In the present work, we briefly review the main conclusions harvested until now in our previous works regarding the WGS reaction together with new results, examples and key ideas for designing WGS catalysts. Most of the ideas and general statements included in the present work may be also very useful for designing catalysts for other reactions that require the presence and combination of metals and oxides. Particularly relevant is the description of the nature, properties and future implications of the nano-mixed-oxide phase “naturally” generated at the interface of some systems which modifies and activates the whole catalytic process. Co-supporting metal and reducible-oxide nanoparticles on another oxide-support in systems with a strong oxide–oxide interaction opens the door to a new family of highly active catalysts suitable for reactions such as water gas shift, CO oxidation or methanol synthesis, among others.