Insight into the Selectivity Mechanism During Formaldehyde Decomposition: Hydrogen or Methanol Production

Abstract Formaldehyde‐water decomposition is promising for hydrogen production due to high hydrogen content. Its decomposition involves complex parallel reactions, but thermodynamically usually yields methanol, not H 2 . Formaldehyde decomposition has several steps, with formic acid as a key intermediate from the formaldehyde–water shift. Organometallic hydrides are crucial catalyst intermediates in both the shift and formic acid decomposition. They overcome energy barriers to react with H + or CH 2 (OH) 2 , determining final products. DFT calculations show an organoruthenium hydride prefers H 2 production via proton coupled electron transfer (PCET), despite higher Gibbs free energy ( Δ r G ) than methanol formation, because methanol production has a high‐barrier step. Alkaline solvent boosts H 2 yield over organorhodium. Formaldehyde could also decompose into hydrogen over organorhodium in a medium‐pressure reactor, as higher temperature facilitates methanol reforming, a novel pathway.