1：Experimental Design and Method Selection:

A two-step calcination process was employed to synthesize IO-TiO2-x. The first step involved the formation of opal photonic crystal templates using polystyrene (PS) spheres, followed by the absorption of TiO2 precursor into the gaps. The second step involved calcination in the presence of dicyandiamide (DCDA) to introduce reduced Ti atoms/oxygen vacancies.

2：Sample Selection and Data Sources:

Monodispersed PS spheres were synthesized and used as templates. TiO2 precursor was prepared using titanium tetraisopropanolate (TTIP).

3：List of Experimental Equipment and Materials:

PS spheres, TTIP, DCDA, and various characterization tools including TEM, FESEM, XRD, EPR, Raman, XPS, UV-DRS, and PL spectroscopy.

4：Experimental Procedures and Operational Workflow:

The synthesis involved the preparation of PS opal templates, infiltration with TiO2 precursor, calcination to remove the template and form IO-TiO2, and a second calcination with DCDA to produce IO-TiO2-x.

5：Data Analysis Methods:

Characterization techniques were used to analyze the structure, composition, and photoelectric properties of the synthesized materials.