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Title: Active site of copper-zinc methanol synthesis catalysts
Plain: Most of the world's methanol is made from carbon oxides and hydrogen over copper particles mixed with zinc oxide. Whether the reaction runs on copper steps decorated with zinc, on a copper-zinc surface alloy, or at the boundary with zinc oxide is still argued.
Precise: For Cu/ZnO/Al2O3 under industrial conditions (about 500 K, $5e7\ \text{to}\ 1e8\ \mathrm{dyn}/\mathrm{cm}^{2}$ of CO/CO2/H2), identify the site responsible for most methanol turnover: Zn-decorated Cu steps (Behrens et al., Science 2012, https://doi.org/10.1126/science.1219831), a Cu-Zn surface alloy whose Zn coverage sets the rate (Kuld et al., Science 2016, https://doi.org/10.1126/science.aaf0718), or the Cu-$\mathrm{ZnO}_{x}$ interface, and whether the site differs for CO2 and CO hydrogenation. An answer is operando identification of site structure correlated with site-normalized rates and reproduced by first-principles kinetics.
Settled by: Operando spectroscopy and microscopy counting candidate sites under reaction conditions, correlated with turnover and with computed kinetics.
Kind: well-posed
Answer type: identification
References: (empty)
Literature status: contested
Status note: Competing assignments published in 2012, 2016 and 2020 (Laudenschleger, Ruland, Muhler, Nature Communications, https://doi.org/10.1038/s41467-020-17631-5) have not been reconciled.
Posed since: (empty)