Xiao-Li Li,Guo-Hui Yang,Meng Zhang,Xiao-Feng Gao,Hong-Juan Xie,Yun-Xing Bai,Ying-Quan Wu,Jun-Xuan Pan,Yi-Sheng Tan
Graphical Tuning selectivity : Cu/SiO 2 was prepared by ammonia evaporation and used as catalyst for the direct synthesis of ethanol from CO hydrogenation. Both the Cu + /(Cu + +Cu 0 ) values and copper crystallite sizes had significant effects on the selectivity towards ethanol. Cu/SiO 2 catalyst was prepared by the ammonia evaporation method for the direct synthesis of ethanol from CO hydrogenation. The catalyst exhibited the initial ethanol selectivity as high as 40.0 wt %, which dramatically decreased from 40.0 to 9.6 wt % on the stream of 50 h. XRD, XPS, TEM and N 2 O titration techniques were employed to elucidate the ethanol selectivity change and catalyst structure evolution during reaction process. The experiment and characterization results indicated that both Cu + /(Cu + +Cu 0 ) value and copper crystallite size had great effects on the ethanol selectivity. During the initial 38 h, the ethanol selectivity obviously decreased from 40.0 to 18.2 wt %, and Cu + /(Cu + +Cu 0 ) value on the catalyst surface rapidly dropped from 0.67 to 0.39, while the copper crystallite size remained almost unchanged. However, during the reaction period of 38–50 h, the Cu + /(Cu + +Cu 0 ) value possessed no distinct change, but a further decrease in ethanol selectivity and a rapid aggregation in Cu particles were observed simultaneously. The present systematic investigation demonstrated that the decrease of Cu + /(Cu + +Cu 0 ) value was the main factor for the loss of ethanol selectivity during the initial 38 h, whereas the rapid growth of Cu particles during the reaction period of 38–50 h were mainly contributed to the further decline of ethanol selectivity.
Sun Hao,Chen Ling,Xiong Likun,Feng Kun,Chen Yufeng,Zhang Xiang,Yuan Xuzhou,Yang Baiyu,Deng Zhao,Liu Yu,Rümmeli Mark H.,Zhong Jun,Jiao Yan,Peng Yang
Electrochemical CO 2 reduction (CO 2 RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings. In this study, the effect of conducting support on the CO 2 RR behaviors of semi-conductive metal-organic framework (MOF) — Cu 3 (HITP) 2 are carefully investigated. Compared to the stand-alone MOF, adding Ketjen Black greatly promotes C 2 H 4 production with a stabilized Faradaic efficiency between 60-70% in a wide potential range and prolonged period. Multicrystalline Cu nano-crystallites in the reconstructed MOF are induced and stabilized by the conducting support via current shock and charge delocalization, which is analogous to the mechanism of dendrite prevention through conductive scaffolds in metal ion batteries. Density functional theory calculations elucidate that the contained multi-facets and rich grain boundaries promote C–C coupling while suppressing HER. This study underlines the key role of substrate-catalyst interaction, and the regulation of Cu crystalline states via conditioning the charge transport, in steering the CO 2 RR pathway.
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