Zhu Wanzhen, Meng Yu, Yang Chaoxin, Zhao Jun, Wang Hongliang, Hu Wei, Lv Guangqiang, Wang Yingxiong, Deng Tiansheng, Hou Xianglin
Shandong Provincial Key Laboratory of Molecular Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China.
Shaanxi Key Laboratory of Low Metamorphic Coal Clean Utilization, School of Chemistry and Chemical Engineering, Yulin University, Yulin 719000, China.
ACS Appl Mater Interfaces. 2021 Oct 20;13(41):48582-48594. doi: 10.1021/acsami.1c12329. Epub 2021 Oct 6.
As the frontier in heterogeneous catalyst, a monomer and positively charged active sites in the single-atom catalyst (SAC), anchored by high electronegative N, O, S, P, etc., atoms, may not be active for the multispecies (O, substrates, intermediates, solvent etc.) involved liquid-phase aerobic oxidation. Here, with catalytic, aerobic oxidation of 5-hydroxymethylfurfural as an example, Pt SAC (Pt-N) was synthesized and tested first. With commercial Pt/C (Pt loading of 5 wt %) as a benchmark, 2,5-furandicarboxylic acid (FDCA) yield of 97.6% was obtained. Pt SAC (0.56 wt %) gave a much lower FDCA yield (28.8%). By changing the coordination atoms from highly electronegative N to low electronegative Co atoms, the prepared Pt single-atom alloy (SAA, Pt-Co) catalyst with ultralow Pt loading (0.06 wt %) gave a much high FDCA yield (99.6%). Density functional theory (DFT) calculations indicated that positively charged Pt sites (+0.712e) in Pt-N almost lost the capability for oxygen adsorption and activation, as well as the adsorption for the key intermediate. In Pt-Co SAA, the central negatively charged Pt atom (-0.446e) facilitated the adsorption of the key intermediate; meanwhile, the nearby Co atoms around the Pt atom constituted the O-preferred adsorption/activation sites. This work shows the difference between the SAC with NPs and the SAA during liquid-phase oxidation of HMF and gives a useful guide in the future single-atom catalyst design in other related reactions.
作为多相催化剂的前沿领域，单原子催化剂（SAC）中的单体和带正电荷的活性位点由高电负性的N、O、S、P等原子锚定，对于涉及多物种（O、底物、中间体、溶剂等）的液相需氧氧化可能不具有活性。在此，以5-羟甲基糠醛的催化需氧氧化为例，首先合成并测试了Pt SAC（Pt-N）。以商业Pt/C（Pt负载量为5 wt%）为基准，2,5-呋喃二甲酸（FDCA）产率达到97.6%。而Pt SAC（0.56 wt%）的FDCA产率则低得多（28.8%）。通过将配位原子从高电负性的N改为低电负性的Co原子，制备的超低Pt负载量（0.06 wt%）的Pt单原子合金（SAA，Pt-Co）催化剂的FDCA产率要高得多（99.6%）。密度泛函理论（DFT）计算表明，Pt-N中带正电荷的Pt位点（+0.712e）几乎失去了氧吸附和活化能力以及对关键中间体的吸附能力。在Pt-Co SAA中，中心带负电荷的Pt原子（-0.446e）促进了关键中间体吸附；同时，Pt原子周围附近的Co原子构成了优先吸附/活化O的位点。这项工作展示了纳米颗粒的SAC和SAA在HMF液相氧化过程中的差异，并为未来其他相关反应的单原子催化剂设计提供了有益指导。
