Zhenzhen Miao,Yibo Zhang,Xiqiang Pan,Tianxiao Wu,Bin Zhang,Jingwei Li,Ting Yi,Zhendong Zhang,Xiangguang Yang
Porous Bi-doped ceria (Ce1−xBixO2−δ solid solution) was prepared by the easy citrate method and then used as a supporting material for Au nanoparticles (NPs) obtained by deposition–precipitation. In the presence of O2, Ce1−xBixO2−δ (0.08 ≤ x ≤ 0.5) efficiently catalyzed the conversion of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HFCA) and 2,5-bishydroxymethylfuran (BHMF) in alkaline aqueous solution without degradation of HMF. The excellent catalytic activity was attributed to the oxygen activation and hydride transfer enhanced by Bi doping and the large amount of oxygen vacancies. After Au NPs were supported on Ce1−xBixO2−δ (x ≤ 0.2), the presence of Auδ+ facilitated the activation of the C–H bond in the hydroxymethyl group and then the production of 2,5-furandicarboxylic acid (FDCA) as an end product, inhibiting the generation of BHMF.
Dong Jiang,Wenzhong Wang,Erping Gao,Ling Zhang,Songmei Sun
For conventional photocatalysis, the energy threshold rather than merely the spectral response is always restricted that the infrared part (48% of solar energy) has never been efficiently utilized, undesirably elevating the temperature and damaging the photon-to-electron conversion. It remains challenging to conquer the IR-related contradiction and integrate the infrared energy into the solar energy conversion. Herein, we logically designed a Bi-induced synergistic photo/thermocatalyst (fluorite Ce1–xBixO2−δ nanorods), where the coupled ionic conductivity accompanying highly reductive Bi and concomitant oxygen vacancies helped bring about integration of photocatalysis with synergistic low temperature (20–80 °C, IR-driven) catalysis, promising for the effective utilization of infrared energy. More generally, through our results a feasible methodology is verified in detail that integration of semiconductor photocatalysis with solid state ionics may help design brand new catalysts, shedding light on the practical solar energy conversion.
Investigation of Bi-doping effects on the catalytic performance of Pt/3DOM-Ce 1−x Bi x O 2−δ in the aerobic oxidation of 5-hydroxymethyl-2-furfural allows us to reveal the promoted catalytically active sites: the asymmetrical oxygen vacancies coordinated with one Bi and up to three Ce cations, such as Bi-□(-Ce) 3 , where □ represents an oxygen vacancy, which can easily gain oxygen atoms in favor of the CeO 2 structure, and, when filled with oxygen, easily release oxygen anions in favor of six-coordination for Bi 3+ . The loss of electrons in the reduction of oxygen atoms at these sites would be replenished by electron transfer from Pt nanoparticles , eventually promoting the oxidation potential of the Pt nanoparticles. The present work points out that the promoted catalytic properties in Bi-doped CeO 2 are mainly due to the asymmetric structures of the oxygen vacancies, rather than simply to the number of oxygen vacancies. The newly proposed model of asymmetrical active sites and electron transfer mechanism may shed light on the physicochemical properties of other solid solution substrate-supported metal nanoparticle catalysts.
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