Thousands of overlooked steps: new model maps the route from CO2 to methanol
Researchers in India expanded a copper catalyst's reaction network from 152 to 9,389 steps. Only then did the model predict the right main products.
Symbolic image · Photo: Sayantan Mondal / Wikimedia Commons, CC BY-SA 4.0 (cropped and resized)
Turning carbon dioxide and hydrogen into methanol is seen as a route to cleaner fuels and chemicals, but exactly how the reaction proceeds on a copper catalyst has not been fully understood. A team at the Indian Institute of Science in Bengaluru combined quantum mechanical simulations with machine learning to find out. The Green R&D Centre of Hindustan Petroleum and Singapore's research agency A*STAR were also involved. The study appeared in Nature Communications.
The original 152-reaction model got it wrong: it predicted formic acid as the main product and underestimated how much CO2 is converted. Expanded to 9,389 reactions involving 105 surface species, it predicted about 40 times more conversion and correctly identified methanol and carbon monoxide as the main products. How do you know the network has not omitted the one step that matters, asked first author Anand M. Verma.
One detail came as a surprise: in several steps, hydrogen is transferred as an intact molecule rather than as separate atoms, especially to oxygen-containing intermediates. Catalysts that interact more strongly with hydrogen molecules could therefore yield more methanol, the authors conclude. They say the method could also be applied to nitrogen reduction and water splitting.