The Al-doped ZnO catalyst has a lower work function, which is conducive to promoting the dissociation of CH_xO* to form CH_x*; it also facilitates the generation of Zn^x+ and oxygen vacancies, which further promotes the generation of C₂₊OH.

Abstract

The direct conversion of syngas into C₂₊OH has attracted significant attention as a potential pathway for energy conversion. However, this process typically requires the use of precious metals or the collaborative action of multi-component catalysts, making it relatively complex. In this paper, simple and economical Al-doped ZnO catalysts were employed for the synthesis of C₂₊OH. The results show that the work function, Zn^x+, and the relative content of oxygen vacancies are linearly related to C₂₊OH/ROH. When the doping amount was 7 mol%, the catalyst had the highest C₂₊OH/ROH (82.6 wt%), corresponding to the lowest work function value, the highest Zn^x+ content, and the relative content of oxygen vacancies. We reveal that the successful synthesis of C₂₊OH depends not only on the low work function of the Al-doped ZnO but also on the existence of the oxygen vacancies and Zn^x+ sites. Specifically, the low work function induced by Al doping facilitates electron transfer in the reaction, facilitating the dissociation of CH_xO* into CH_x*. Meanwhile, the presence of oxygen vacancies enhances the dissociative adsorption capacity of CO and facilitates the formation of CH_x* species. The Zn^x+ sites serve as active centers for carbon chain growth, promoting C–C coupling through the insertion of CO or CH_xO* into CH_x*, thereby achieving chain elongation.