Electronic control of catalytic activity of ZnO for higher alcohols synthesis via tailoring Fermi level

Abstract

Metal doping are essential for electronic modulation of semiconductors, leading to different Fermi level, which determined the surface chemisorption and catalytic properties. Here, ZnO doping with 4 mol% Cu were synthesized by four preparation routes, which tuned Cu existing states and Fermi level appearing remarkable impacts on the catalytic performance of catalysts. It shows a negative correlation between synthesis of higher alcohols and Fermi level over electronically modified ZnO catalysts, and the lower Fermi level exerted better facilitation for the carbon chain growth. Copper was incorporated into ZnO lattice and existed in the form of isolated Cu2+, which regulated the electronic structure of ZnO with lower Fermi level and boosted the process of catalysts obtaining electrons. Thus, the lower Fermi level promoted the dissociation CO bond and p-type reaction of forming surface alkyl species, and a higher proportion of straight chain higher alcohols can be achieved via CO or CHxO* inserting into alkyl species. Especially the catalyst prepared by urea hydrolysis with the lowest Fermi level significantly increased the higher alcohols fraction in total alcohol products to 69.9%. For comparison, the higher Fermi level are unfavorable for p-type reaction, leading to high methanol selectivity. This work provides a new viewpoint for promoting catalytic performance from the perspective of electronic modification of ZnO.