The roles of Rh crystal phase and facet in syngas conversion to ethanol

Design of Rh catalyst by controlling crystal phase and facet is significant for providing higher mass-specific activity and selectivity for ethanol synthesis from syngas. We demonstrate here the roles of crystal phase and facet in syngas conversion to ethanol on different crystal facets of fcc and hcp Rh by DFT calculations and microkinetic modeling. Compared to hcp Rh, fcc Rh not only exhibits higher intrinsic activity for CH and ethanol formation, but also exposes much denser active facets and inhibits methanol, especially, the mainly exposed (1 1 1). Further, for the Fe-modified Rh catalysts, fcc Rh exhibits better activity and selectivity toward ethanol, which is still superior to hcp Rh. Thus, Rh-based catalysts should be focused on the fcc crystal phase instead of hcp crystal phase. The findings in this work are significantly beneficial to the rational design of Rh-based catalysts for CO hydrogenation to desired ethanol.