Abstract Co/Rh heterobimetallic nanoparticles were prepared from cobalt-rhodium carbonyl clusters [Co 2 Rh 2 (CO) 12 and Co 3 Rh (CO) 12] and immobilized on charcoal. HR-TEM revealed that the size of the heterobimetallic nanoparticles was ca. 2 nm and ICP-AES analysis showed a 2: 2 and a 3: 1 cobalt-rhodium stoichiometry (Co 2 Rh 2 and Co 3 Rh 1) in the heterobimetallic nanoparticles. The Co/Rh heterobimetallic nanoparticles ...