To reduce the cost of noble metal catalyst, it is important to find the balance point between higher atomic utilization and catalytic ensemble-requirement. The ensemble requirement could be described as the minimum number of metal atoms and the corresponding spatial arrangement that is needed to catalyse a specific reaction most efficiently. The famous examples for ensemble requirement include the so-called C₇ center over iron and the B5 center over Ru for N₂ activation. There is a type of catalysts, namely fully-exposed cluster catalyst (FECC), which can not only provide the catalytic sites with multiple metal atoms, but also maintain a full atomic utilization efficiency. FECC is so highly dispersed that all the metal atoms within it are available for the adsorption and transformation of reactants. Here, with dodecahydro-N-ethylcarbazole (DNEC) as a representative substrate of liquid organic hydrogen carrier, we identified that the fully-exposed Pd clusters with an average Pd–Pd coordination number around of 4.4 acting as the optimal sites towards efficient hydrogen recovery. The extension of the concept of fully-exposed metal clusters (FECC) would allow for the design of advanced metal catalysts to achieve a higher mass-specific activity without wasting the metal loading inside particles or as inactive single-atoms.