5 years ago

Significance of Surface Formate Coverage on the Reaction Kinetics of Methanol Synthesis from CO2 Hydrogenation over Cu

Significance of Surface Formate Coverage on the Reaction Kinetics of Methanol Synthesis from CO2 Hydrogenation over Cu
Panpan Wu, Bo Yang
The hydrogenation of CO2 to methanol over copper-based catalysts has attracted considerable attention recently. Among all the proposed reaction mechanisms, a large number of experimental and theoretical studies have focused on the one that includes a HCOO intermediate due to the fact that high coverages of formate over catalyst surfaces were observed experimentally. To systematically understand the influence of formate species coverage on the reaction kinetics of methanol synthesis, the energetics of the CO2 hydrogenation pathway over clean and one- or two-formate preadsorbed Cu(211) are obtained using density functional theory calculations, and these energetics are further employed for microkinetic modeling. We find that the adsorption energies of the intermediates and transition states involved in the reaction pathway are changed in the presence of spectating formate species, and consequently, the potential energy diagrams are varied. Microkinetic analysis shows that the turnover frequencies (TOFs) over different formate preadsorbed surfaces vary under the same reaction condition. In particular, the reaction rates obtained over clean Cu(211) are generally the lowest, while those over one- or two-formate preadsorbed surfaces depend on the reaction temperatures and pressures. Meanwhile, we find that only when the formate coverage effect is considered, some of the TOFs obtained from microkinetic modeling are in fair agreement with previous experimental results under similar conditions. After the degree of rate control analysis, it is found that the combination of HCOO and HCOOH hydrogenation steps can be treated as the “effective rate-determining step”, which can be written as HCOO* + 2H* → H2COOH* + 2*. Therefore, the formation of methanol is mainly controlled by the surface coverage of formate and hydrogen at the steady state, as well as the free energy barriers of the effective rate-determining step, i.e., effective free energy barriers.

Publisher URL: http://dx.doi.org/10.1021/acscatal.7b01910

DOI: 10.1021/acscatal.7b01910

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.