Langmuir-Blodgett Monolayer of Cobalt Phthalocyanine as Ultralow Loading Single-Atom Catalyst for Highly Efficient H 2 O 2 Production.

The electrochemical production of H 2 O 2 via the two-electron oxygen-reduction reaction (2e - ORR) has been actively studied using systems with atomically dispersed metal-nitrogen-carbon (M-N-C) structures. However, the development of well-defined M-N-C structures that restrict the migration and agglomeration of single-metal sites remains elusive. Herein, we demonstrate a Langmuir-Blodgett (LB) monolayer of cobalt phthalocyanine (CoPc) on monolayer graphene (LB CoPc/G) as a single-metal catalyst for the 2e - ORR. The as-prepared CoPc LB monolayer has a β-form crystalline structure with a lattice space for the facile adsorption of oxygen molecules on the cobalt active sites. The CoPc LB monolayer system provides highly exposed Co atoms in a well-defined structure without agglomeration, resulting in significantly improved catalytic activity, which is manifested by a very high H 2 O 2 production rate per catalyst (31.04 mol g cat -1 h -1 ) and TOF (36.5 s -1 ) with constant production stability for 24 hours. To the best of our knowledge, the CoPc LB monolayer system exhibits the highest H 2 O 2 production rate per active site. This fundamental study suggests that an LB monolayer of molecules with single-metal atoms as a well-defined structure works for single-atom catalysts.