Involvement of the Unoccupied Site Changes the Kinetic Trend Significantly: A Case Study on Formic Acid Decomposition

A qualified heterogeneous catalyst for formic acid decomposition (FAD) should ensure a good H-2 production activity and an extremely low CO selectivity. Previous theoretical study applied the well-established Norskov-Bligaard method to screen catalysts for FAD, while some kinetic models for HCOO* and COOH* dehydrogenation involved no extra unoccupied site, which was necessary in some other kinetic models. In the present work, we use FAD as a case study to comprehensively investigate the effects of different kinetic models on the calculated maps for the predictions of the reaction activity and selectivity. The results show that trends of the predicted CO selectivity are significantly different over a series of transition-metal surfaces for two kinetic models, yielding different predictions for catalyst candidates of FAD. Our results call for a close attention to mechanism details in a theoretical catalyst design.