A trinuclear cobalt complex, a new electrocatalyst for oxygen reduction to H2O2

Abstract

• Reaction of amine-bis(phenolate) ligand (H 2 L) and Co(CH 3 CO 2 ) 2 gives a trinuclear cobalt complex, [L 2 Co 3 (CH 3 O)(CH 3 CO 2 ) 2 ]. • This complex can electro-catalyze oxygen reduction with almost 100% H 2 O 2 selectivity in 0.20 M KOH. • Catalytic activity can be attributed to the dissociation of CH 3 O - , allowing O 2 to bind. The reaction of 2-pyridylamino-N,N-bis(2-methylene-4,6-bimethyl)phenol (H 2 L) and Co(CH 3 CO 2 ) 2 affords a new trinuclear cobalt complex, [L-Co-μ(CH 3 CO 2 )-μ(CH 3 O)-Co-μ(CH 3 CO 2 )-μ(CH 3 O)-Co-L], which has been characterized by using physics-chemical and spectroscopic methods. Electrochemical investigations exhibit that this cobalt complex can serve as an electro-catalyst for oxygen reduction reaction (ORR). Under -0.4 V vs Ag/AgCl, the H 2 O 2 yield is almost 100% in 0.20 M KOH. Studies indicate that the dissociation of CH 3 O - group from the trinuclear cobalt complex makes empty positions on cobalt centres, amenable to binding to dioxygen (O 2 ) for the formation of H 2 O 2 or H 2 O.