Yumei Jian,Ye Meng,Jie Li,Hongguo Wu,Shunmugavel Saravanamurugan,Hu Li
Photocatalytic reductive conversion of bio-derivatives to biofuels and fine chemicals is an eco-friendly and energy-saving way for biomass valorization. Herein, we developed a new and high-performance protocol for control of activity/selectivity in photocatalytic reductive upgrading of biomass to biofuels at room temperature via engineering oxygen vacancy (Ov) and manipulating the exposed crystal surfaces of the TiO 2 -based catalysts, such as efficient cascade photocatalytic hydrogenation-cyclization of ethyl levulinate to γ-valerolactone in water (up to 96% yield, TOF: 112.1 h −1 ), and the selective conversion of 5-methylfurfural to 5-methylfurfuryl alcohol (90% yield) or long carbon-chain coupling products (86% yield) in methanol, respectively. The {101} crystal plane is prone to produce more Ov in situ than the {001} and {110} crystal planes. The formation of Ov was not only beneficial to the adsorption and activation of the bio-based carbonyls, but also could enhance the migration efficiency of the photo-generated carriers and effectively adjust the semiconductor band structure of the TiO 2 -based photocatalyst to promote the visible-light absorption, thus enhancing the overall reductive conversion process, as elucidated by DFT calculations. Also, the charge distribution and adsorption intensity of different exposed crystal surfaces of the photocatalyst were able to control the selectivity of the bioproducts . In addition, the optimal Ov-TiO 2− x {101} catalyst had excellent reusability and could be reused at least five times with no obvious decrease in photocatalytic performance. The strategy of selectivity control via engineering the catalyst exposed crystal surfaces and loaded Ov provides an opportunity for multi-catalytic biomass conversion to biofuels.
A method has been developed for controlled epitaxial growth on cubic nanocrystals by selectively activating their surface via etching. For example, it produces Pd concave nanocubes via seeding growth on their corners and edges, and in turn, formulates highly active sites for catalysis. This method offers a better capability of preventing atomic addition on undesired locations and maintaining particle size in the seeding process, as compared with the previous technique. With the particle size well maintained, the products fully exhibit superior electrocatalytic performance enabled by active sites and high-index facets in formic acid oxidation. Another contribution of this work is to enable the growth of a noble metal with high catalytic activities on another type of cheaper metal, which greatly reduces the usage of expensive materials while retaining high catalytic activity. In this article, we have demonstrated the deposition of a very limited amount of Pt (only 3.3 wt%) on Pd nanocrystals towards high electrocatalytic activities in an oxygen reduction reaction. Preliminary studies demonstrate that the synthetic strategy can be also applied to the controllable deposition of a different material on the faces of a nanocrystal by simply altering surface conditions.
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