An increasing energy demand and a pressing need for sustainable, low-emission solutions have increased the use of renewable energy sources such as wind and solar energy. However, the intermittent nature of these sources has led to the development of efficient energy storage systems for stable supply of electrical power for household and transportation applications. Chemical storage of energy via hydrogen offers an attraction option due to a high gravimetric energy storage density (33 kWh kg-1) [1]. Formic acid (FA) and formate salts (FS) are considered as potential candidates because they are abundant, inexpensive and have low environmental toxicity. Palladium has been identified as a promising (de-)hydrogenation catalyst, albeit the conversion efficiency and yield of H2 in the CO2/H2CO2 or HCO3/HCOO cycle is strongly influenced by the reaction environment and the operating conditions [2, 3]. The type of catalyst support as well as solution composition, temperature and pH all impact the reaction rates and mechanism, though a molecular understanding of such impacts are not comprehensively understood. Here, we employ a coupled quantum mechanics/molecular mechanics (QM/MM) scheme [4] to investigate the role played by the reaction environment and operating conditions on the reactivity of FA and FS decomposition. By varying the concentration and identity of solution phase ions, we investigate the effect of solution composition on the reaction energetics and binding strength of reaction intermediates on palladium. The results of these studies allow molecular-scale mechanistic determination using nuanced, dynamical models of the solvated catalyst interface and provide a rationale for improved environment driven design and optimization of H2 storage using formic acid or formate salts-based carriers.

Environment based tuning of formic acid/formate salts as hydrogen carriers using heterogeneous catalysis

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.