Al12Co4: a pioneering heterometallic aluminum oxo cluster with surface-exposed Co sites for the oxygen evolution reaction.

We report an unprecedented heterometallic aluminum oxo cluster (AlOC) containing four surface-exposed Co II sites, designated as Al12Co4, protected by four t -butylcalix[4]arene (TBC[4]) molecules. The Al 12 Co 4 nanocluster represents a significant advancement on multiple innovative fronts. First, it stands as an pioneering example of an Al III -based metallocalixarene nanocluster. It is also the first instance of heterometallic AlOCs shielded by macrocyclic ligands. Notably, this cluster also holds the distinction of being the highest nuclearity Al-Co bimetallic nanocluster known to date. Additionally, by depositing Al12Co4 on carbon nanotubes (CNTs) as a supported catalyst, we investigated its electrocatalytic performance for the oxygen evolution reaction in alkaline media. To reach a 10 mA cm -2 current density in alkaline solution, the Al12Co4@CNT electrode needs overpotential as low as 320 mV.