Photocatalytic and Electrocatalytic Properties of Cu-Loaded ZIF-67-Derivatized Bean Sprout-Like Co-TiO(2)/Ti Nanostructures

ZIF-derivatized catalysts have shown high potential in catalysis. Herein, bean sprout-like Co-TiO(2)/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(3)O(4). The head of the bean sprout structure was observed to be Co(3)O(4), while the stem showed a crystal structure of rutile TiO(2) grown from the metallic Ti support. Cu sputter-deposited Co-TiO(2)/Ti nanostructures were also prepared for photocatalytic and electrocatalytic CO(2) reduction performances, as well as electrochemical oxygen reaction (OER). Gas chromatography results after photocatalytic CO(2) reduction showed that CH(3)OH, CO and CH(4) were produced as major products with the highest MeOH selectivity of 64% and minor C(2) compounds of C(2)H(2), C(2)H(4) and C(2)H(6). For electrocatalytic CO(2) reduction, CO, CH(4) and C(2)H(4) were meaningfully detected, but H(2) 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(2)/Ti hybrid nanostructures and their applications to CO(2) reduction and electrochemical water splitting in energy and environmental fields.