Highly Efficient Photocatalytic Conversion of Gas-Phase CO2 Using Bimetallic Porphyrin-Sensitized TiO2 Nanotube Arrays

Solar-powered photocatalytic conversion of CO2 into green solar fuels is one of the effective ways to solve the global energy crisis and the greenhouse effect. A new artificial photosynthesis system composed of TiO2 nanotube arrays (TiO2NTs) and bimetallic porphyrin was fabricated, and their photocatalytic activities were evaluated by the reduction of gas-phase CO2 to CH4 under simulated solar irradiation. Compared to pure TiO2NTs and CoTCPP/TiO2NTs, bimetallic porphyrin-sensitized TiO2NTs displayed greatly ameliorated photocatalytic activity. Among them, Ni-CoTCPP/TiO2NTs exhibited the highest photoreduction efficiency, and the reduction rate of CO2 into CH4 was up to 52.27 μmol/cm2/h with the quantum efficiency of 1.002%, about 7 times higher than that of pure TiO2NTs. The increase in photocatalytic performance can be attributed to the enhancement of the light absorption capacity of Ni-CoTCPP/TiO2NTs and the higher charge separation efficiency. Furthermore, according to the results of the photocatalytic evaluation and photo(electro)chemical studies, a possible mechanism of CO2 photoreduction over Ni-CoTCPP/TiO2NTs was proposed.