Figure 1. The challenge of reaction network complexity in catalyst discovery.

(a) Reaction network for the reaction of syngas (CO+H₂) to CO₂, water, methane, methanol, acetaldehyde and ethanol, including surface-adsorbed intermediates with up two carbons and two oxygens (C1/C2 chemistries). Even for this reduced network, there are hundreds of reactions and thousands of possible mechanisms to consider for each new catalyst active site, which are prohibitively expensive for materials discovery screens. (b) The reduced network for syngas reactivity on Rh(1 1 1), producing acetaldehyde selectively as confirmed by the experiment. The reduction from (a) to this subset is made more efficient and uses far fewer full-accuracy DFT calculations using the methods in this work.