Ferrite@TiO2-nanocomposites as Z-scheme photocatalysts for CO2 conversion: Insight into the correlation of the Co-Zn metal composition and the catalytic activity

•Hierarchical CoxZn1-xFe2O4@TiO2 nanocomposites were successfully synthesized.•Strong interconnection was observed between maximum yield of CO and CH4 products and Co/Zn ratio.•Selectivity towards CH4 and CO2 was varied by tuning the Co/Zn ratio.•Z-scheme mechanism was proven by detailed electrochemistry analyses.