Electrocatalysis plays a key role in the energy conversion processes that are central to renewable energy technologies such as fuel cells and artificial photosynthesis. A rational design of catalyst relies on our understanding of structure-activity relationships and identification of catalytically active sites. So far, numerous efforts have been made to optimize nanostructured catalysts by tuning their size, composition, and shape, while new design principles are essential for electroreduction catalysis such as CO₂ recycling using renewable electricity. Here we show that grain boundaries (GBs) in metal nanoparticles create new active sites for electroreduction catalysis. Through a careful design of metal nanoparticle catalysts with different GB densities, extensive TEM characterization, and electrochemical measurements, we found that the catalytic activity for CO₂ reduction on Au and CO reduction on Cu is directly correlated with GB density in the catalysts [1, 2]. The quantitative GB-activity relationships indicate that GBs in metal nanoparticles create new active sites for electroreduction catalysis and lead to highly active and stable catalysts for a two-step electrochemical conversion of CO₂ to liquid fuels such as ethanol and acetate. In addition, we found that GBs in Au enhance its activity for oxygen reduction reaction, which suggests that GB engineering is a general strategy for improving electrocatalytic activity for renewable energy conversion.

References:

(1) Feng, X.; Jiang, K.; Fan, S.; Kanan, M. W. J. Am. Chem. Soc. 2015, 137, 4606–4609.

(2) Feng, X.; Jiang, K.; Fan, S.; Kanan, M. W. ACS Cent. Sci. 2016, 2, 169−174.