Facile and accelerated production of RuO2 monolayers via a dual-step intercalation process

Tetrabutylammonium ions (TBA(+)) have commonly been used to exfoliate RuO2 into monolayers via ion exchange reactions. However, the low production yield of RuO2 exfoliation, which originates from the large molecular size of TBA(+), limits wider utilisation of RuO2 monolayers in optoelectronic applications. We introduce a rapid and efficient dual-step exfoliation process beginning with intercalation of small organic molecules (tetramethylammonium ions) into RuO2, which is followed by the addition of TBA(+) as a second intercalant to realize RuO2 monolayer production. Our dual-step intercalation process increases the RuO2 monolayer exfoliation yield from 9.9% to 60% after 14 days. Density functional theory calculations reveal that the activation energy of dual-step intercalation is much lower than that of direct intercalation of TBA(+) ions into the RuO2 structure. The experimental and theoretical results of dual-step intercalation suggest that it is a facile and general approach for the production of metal oxide monolayers, and could widen the use of metal oxide monolayer nanosheets.