Lewis Acid Strength of Interfacial Metal Sites Drives CH₃OH Selectivity and Formation Rates on Cu‐Based CO₂ Hydrogenation Catalysts

Abstract

CH3OH formation rates in CO2 hydrogenation on Cu‐based catalysts sensitively depend on the nature of the support and the presence of promoters. In this context, Cu nanoparticles supported on tailored supports (highly dispersed M on SiO2; M=Ti, Zr, Hf, Nb, Ta) were prepared via surface organometallic chemistry, and their catalytic performance was systematically investigated for CO2 hydrogenation to CH3OH. The presence of Lewis acid sites enhances CH3OH formation rate, likely originating from stabilization of formate and methoxy surface intermediates at the periphery of Cu nanoparticles, as evidenced by metrics of Lewis acid strength and detection of surface intermediates. The stabilization of surface intermediates depends on the strength of Lewis acid M sites, described by pyridine adsorption enthalpies and 13C chemical shifts of ‐OCH3 coordinated to M; these chemical shifts are demonstrated here to be a molecular descriptor for Lewis acid strength and reactivity in CO2 hydrogenation.

Tuning product selectivity ofCO2hydrogenation byOHgroups on Pt/γ‐AlOOHand Pt/γ‐Al2O3catalysts

“…[1][2][3][4][5][6][7][8][9][10] Some studies implied that the catalyst's OH groups promoted reactant adsorption on catalysts to improve reactant conversion, whereas some studies suggested that OH groups occupied active sites of catalysts to prevent reactant conversion. [4][5][6][7][8][9][10] Moreover, most of the previous works explored the influence of catalyst's OH groups on heterogeneous catalytic reactions as a whole, and the exact roles of OH groups at different sites of catalysts in heterogeneous catalytic reactions have not been well distinguished yet. [5][6][7][8][9] Besides, traditional ways to prepare heterogeneous catalysts often involve calcination or/and H 2 -reduction at temperatures higher than 400 C at which OH groups can be easily destroyed.…”

“…The OH groups on catalysts were key factors affecting CO 2 hydrogenation efficiency. [5][6][7][8][9][10] The OH groups on Ni/γ-Al 2 O 3 catalyst were proposed to be able to tune the reaction pathway of CO 2 hydrogenation, with formate formation preferred on Ni/γ-Al 2 O 3 without OH groups but CO formation more facile on Ni/γ-Al 2 O 3 with OH groups. 8 Ye et al reported that the OH groups on a Pd/In 2 O 3 catalyst changed a key intermediate of CO 2 hydrogenation from CH 3 O to H 2 COH, and thus vary the CH 3 OH selectivity in CO 2 hydrogenation.…”

“…[2][3][4][5] This also makes the study on the exact roles of OH groups in heterogeneous catalytic reactions very difficult. CO 2 hydrogenation is a very attractive heterogeneous catalytic reaction, as it not only alleviates CO 2 emission but also produces valuable chemicals, such as CH 4 and CO. [5][6][7][8][9][10] However, CO 2 hydrogenation efficiency, especially product selectivity, is still far below the needs of commercialization. The OH groups on catalysts were key factors affecting CO 2 hydrogenation efficiency.…”

“…ever, the exact roles of OH groups in heterogeneous catalytic reactions are still controversial. [1][2][3][4][5][6][7][8][9][10] Some studies implied that the catalyst's OH groups promoted reactant adsorption on catalysts to improve reactant conversion, whereas some studies suggested that OH groups occupied active sites of catalysts to prevent reactant conversion. [4][5][6][7][8][9][10] Moreover, most of the previous works explored the influence of catalyst's OH groups on heterogeneous catalytic reactions as a whole, and the exact roles of OH groups at different sites of catalysts in heterogeneous catalytic reactions have not been well distinguished yet.…”

“…[4][5][6][7][8][9][10] Moreover, most of the previous works explored the influence of catalyst's OH groups on heterogeneous catalytic reactions as a whole, and the exact roles of OH groups at different sites of catalysts in heterogeneous catalytic reactions have not been well distinguished yet. [5][6][7][8][9] Besides, traditional ways to prepare heterogeneous catalysts often involve calcination or/and H 2 -reduction at temperatures higher than 400 C at which OH groups can be easily destroyed. [2][3][4][5] This also makes the study on the exact roles of OH groups in heterogeneous catalytic reactions very difficult.…”