Baokun Huang

An acid-free medium growth of rutile TiO2 nanorods arrays and their application in perovskite solar cells

The facile hydrothermal synthesis of rutile TiO2 nanorod arrays on FTO substrates without the use of acids has been developed. The morphology of the nanorods can be finely tuned by changing the growth parameters, and the potential of the as-made rutile TiO2 nanorods in perovskite solar cells was evaluated, showing power conversion efficiencies up to 11.1%.

Directly Probing Charge Separation at Interface of TiO2 Phase Junction

Phase junction is often recognized as an effective strategy to achieve efficient charge separation in photocatalysis and photochemistry. As a crucial factor to determine the photogenerated charges dynamics, there is an increasingly hot debate about the energy band alignment across the interface of phase junction. Herein, we reported the direct measurement of the surface potential profile over the interface of TiO2 phase junction. A built-in electric field up to 1 kV/cm from rutile to anatase nanoparticle was detected by Kelvin Probe Force Microscopy (KPFM). Home-built spatially resolved surface photovoltage spectroscopy (SRSPS) supplies a direct evidence for the vectorial charge transfer of photogenerated electrons from rutile to anatase. Moreover, the tunable anatase nanoparticle sizes in TiO2 phase junction leads to high surface photovoltage (SPV) by creating completely depleted space charge region (SCR) and enhancing the charge separation efficiency. The results provide a strong basis for understanding the impact of built-in electric field on the charge transfer across the interface of artificial photocatalysts.

Substrate–Electrode Interface Engineering by an Electron-Transport Layer in Hematite Photoanode

The photoelectrochemical water oxidation efficiency of photoanodes is largely limited by interfacial charge-transfer processes. Herein, a metal oxide electron-transport layer (ETL) was introduced at the substrate-electrode interface. Hematite photoanodes prepared on Li(+)- or WO3-modified substrates deliver higher photocurrent. It is inferred that a Li-doped Fe2O3 (Li:Fe2O3) layer with lower flat band potential than the bulk is formed. Li:Fe2O3 and WO3 are proved to function as an expressway for electron extraction. Via introducing ETL, both the charge separation and injection efficiencies are improved. The lifetime of photogenerated electrons is prolonged by 3 times, and the ratio of surface charge transfer and recombination rate is enhanced by 5 times with Li:Fe2O3 and 125 times with WO3 ETL at 1.23 V versus reversible hydrogen electrode. This result indicates the expedited electron extraction from photoanode to the substrate can suppress not only the recombination at the back contact interface but also those at the surface, which results in higher water oxidation efficiency.

Chiral Sulfur Compounds Studied by Raman Optical Activity: tert-Butanesulfinamide and its Precursor tert-Butyl tert-Butanethiosulfinate

Two chiral sulfur compounds, tert-butyl tert-butanethiosulfinate (1) and tert-butanesulfinamide (2), with inversion of configuration, have been studied by Raman optical activity (ROA) and electronic circular dichroism combined with density functional theory calculation. With the S-S linkage in 1, the couplings between the two tertiary carbon atoms often generate large ROA signals, whereas the tertiary carbon atom itself generally makes a large contribution to ROA signals in 2 for similar vibrational modes. The conformational dependence of ROA parameters provides probing conformation around the S-S bond from a new perspective. The simultaneous use of electronic circular dichroism and ROA is warranted to extract reliable conformational information. ROA provides a suitable candidate for the stereochemical study of chiral sulfur compounds, especially its capability of sensing the conformation around the S-S bond.