Artificial Photosynthesis on TiO2-Passivated InP Nanopillars.


Here, we report photocatalytic CO2 reduction with water to produce methanol using TiO2-passivated InP nanopillar photocathodes under 532 nm wavelength illumination. In addition to providing a stable photocatalytic surface, the TiO2-passivation layer provides substantial enhancement in the photoconversion efficiency through the introduction of O vacancies associated with the nonstoichiometric growth of TiO2 by atomic layer deposition. Plane wave-density functional theory (PW-DFT) calculations confirm the role of oxygen vacancies in the TiO2 surface, which serve as catalytically active sites in the CO2 reduction process. PW-DFT shows that CO2 binds stably to these oxygen vacancies and CO2 gains an electron (-0.897e) spontaneously from the TiO2 support. This calculation indicates that the O vacancies provide active sites for CO2 absorption, and no overpotential is required to form the CO2(-) intermediate. The TiO2 film increases the Faraday efficiency of methanol production by 5.7× to 4.79% under an applied potential of -0.6 V vs NHE, which is 1.3 V below the E(o)(CO2/CO2(-)) = -1.9 eV standard redox potential. Copper nanoparticles deposited on the TiO2 act as a cocatalyst and further improve the selectivity and yield of methanol production by up to 8-fold with a Faraday efficiency of 8.7%.

DOI: 10.1021/acs.nanolett.5b02511

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@article{Qiu2015ArtificialPO, title={Artificial Photosynthesis on TiO2-Passivated InP Nanopillars.}, author={Jing Qiu and Guangtong Zeng and Mai-Anh Ha and Mingyuan Ge and Yongjing Lin and Mark Hettick and B. R. Hou and Anastassia N. Alexandrova and Ali Javey and Stephen B Cronin}, journal={Nano letters}, year={2015}, volume={15 9}, pages={6177-81} }