| Summary: | ZIF-derivatized catalysts have shown high potential in catalysis. Herein, bean sprout-like Co-TiO<sub>2</sub>/Ti nanostructures were first synthesized by thermal treatment at 800 °C under Ar-flow conditions using sacrificial ZIF-67 templated on Ti sheets. It was observed that ZIF-67 on Ti sheets started to thermally decompose at around 350 °C and was converted to the cubic phase Co<sub>3</sub>O<sub>4</sub>. The head of the bean sprout structure was observed to be Co<sub>3</sub>O<sub>4</sub>, while the stem showed a crystal structure of rutile TiO<sub>2</sub> grown from the metallic Ti support. Cu sputter-deposited Co-TiO<sub>2</sub>/Ti nanostructures were also prepared for photocatalytic and electrocatalytic CO<sub>2</sub> reduction performances, as well as electrochemical oxygen reaction (OER). Gas chromatography results after photocatalytic CO<sub>2</sub> reduction showed that CH<sub>3</sub>OH, CO and CH<sub>4</sub> were produced as major products with the highest MeOH selectivity of 64% and minor C<sub>2</sub> compounds of C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>4</sub> and C<sub>2</sub>H<sub>6</sub>. For electrocatalytic CO<sub>2</sub> reduction, CO, CH<sub>4</sub> and C<sub>2</sub>H<sub>4</sub> were meaningfully detected, but H<sub>2</sub> was dominantly produced. The amounts were observed to be dependent on the Cu deposition amount. Electrochemical OER performances in 0.1 M KOH electrolyte exhibited onset overpotentials of 330–430 mV (vs. RHE) and Tafel slopes of 117–134 mV/dec that were dependent on Cu-loading thickness. The present unique results provide useful information for synthesis of bean sprout-like Co-TiO<sub>2</sub>/Ti hybrid nanostructures and their applications to CO<sub>2</sub> reduction and electrochemical water splitting in energy and environmental fields.
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