The electron transfer (ET) from the conduction band of the semiconductor to surface-bound species is a key step in the photocatalytic reaction and strongly affects the reactivity and selectivity, while the effect of catalyst surface structure on this process has rarely been explored due to the lack of an effective method. Herein, we have developed a strategy to detect and measure surface electrons' transfer energy to the adsorbates and disclosed a facet-dependent electron transfer energy over anatase TiO 2 . The photogenerated electrons are shallowly confined in the fivecoordinated Ti atom (Ti 5c ) on the surface of the (101) facet with a transfer energy below 1.0 eV, while deeply confined in the sixcoordinated Ti atom (Ti 6c ) on the subsurface of the (001) facet with a transfer energy higher than 1.9 eV. The different electron trap states strongly affect the ET process, thus regulating the photocatalytic activity. Taking formic acid (FA) dehydration as the probe reaction, a shallow trap of photoexcited electrons on the (101) facet of anatase TiO 2 favors the dehydration of FA to CO, while a deep trap of photoexcited electrons on the (001) facet makes FA stable. Based on this knowledge, we successfully controlled the selectivity in the photocatalytic oxidation of biopolyols via selectively exposing the facet of TiO 2 . Through controlling the (001)/ (101) facet, a wide range of biopolyols can be selectively converted into FA or CO with a selectivity of up to 80%. The present work disclosed a facet-dependent electron transfer process and provides a new horizon to the design of photocatalytic systems.
CO and H 2 evolution from renewable and abundant biomass represent a sustainable way, but is challenged to be produced under mild conditions. Herein, we propose to produce CO and H 2 from biomass via a divided photoelectrochemical (PEC) cell at room temperature. Nitrogen doped tungsten trioxide (N-WO 3 ) photoanode reforms biopolyols to CO and H + , and platinum cathode reduces H + to H 2 , achieving CO evolution rate of 45 mmol m À 2 h À 1 (> 75 % gas selectivity) and H 2 evolution rate of 237 mmol m À 2 h À 1 with purity > 99.99 % from glycerol. The nitrogen doping induces structure polarity of WO 3 photoanode, leading to the formation of an internal electric field which promotes the separation and transfer of the photoinduced charges and improves PEC efficiency. A wide range of biopolyols, such as ethylene glycol, xylose, fructose, glucose, sucrose, lactose, maltose, and inulin were effectively converted into CO and H 2 . This work provides a promising method to produce highly pure H 2 together with CO from biomass.
Producing renewable biofuels from biomass is a promising way to meet future energy demand. Here, we demonstrated a lignin to diesel route via dimerization of the lignin oil followed by hydrodeoxygenation. The lignin oil undergoes CÀC bond dehydrogenative coupling over Au/CdS photocatalyst under visible light irradiation, co-generating diesel precursors and hydrogen. The Au nanoparticles loaded on CdS can effectively restrain the recombination of photogenerated electrons and holes, thus improving the efficiency of the dimerization reaction. About 2.4 mmol g catal À1 h À1 dimers and 1.6 mmol g catal À1 h À1 H 2 were generated over Au/CdS, which is about 12 and 6.5 times over CdS, respectively. The diesel precursors are finally converted into C16-C18 cycloalkanes or aromatics via hydrodeoxygenation reaction using Pd/C or porous CoMoS catalyst, respectively. The conversion of pine sawdust to diesel was performed to demonstrate the feasibility of the lignin-to-diesel route.Scheme 1. The Scheme for upgrading of lignin oil.
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