Unveiling the Gold Facet Effect in Selective Oxidation of 5-Hydroxymethylfurfural and Hydrogen Production
Qizhen Qin, Tan Li, Xuehao Sun, An Pei, Yanyan Jia, Hongpeng He, Fan Gao, Peng Wang, Qiqi Wu, Renfeng Liu, Sheng Dai, Haixin Lin, Qingfeng Zhang, Yun Zhao, Guangxu Chen
Abstract
Direct oxidation of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), crucial for medical supply production, is hindered by overoxidation. We synthesized gold nanomaterials with distinct single-crystal facets, {111} in octahedra (OC), {100} in nanocubes (NCs), and {110} in rhombic dodecahedra (RD), to investigate the facet-dependent HMF oxidation. The Au RD achieved the spontaneous oxidation of HMF to HMFCA with stoichiometric hydrogen production, maintaining 95% carbon balance, 91% yield, and 98% selectivity. In contrast, Au OC and NCs were inert. The superior performance is due to the absence of a C–H activation energy barrier on the Au(110) facet. Furthermore, gas chromatography and isotope experiments supported that the intermediate is oxidized to produce H 2 via H – transfer, rather than H 2 O via H + transfer. Oxygen was essential for scavenging electrons, thereby closing the reaction loop. The Au RD exhibited remarkable stability, operating for 240 h without performance degradation, indicating its potential for efficient HMFCA production.