A Simple and Inexpensive Organometallic Compound Catalyzing Oxygen Reduction Reaction

Abstract

One of the major obstacles in fuel cell commercialization is the cost of the precious metal catalysts used for oxygen reduction reaction (ORR) and hydrogen oxidation reaction(1). Recently, non-precious metal catalysts are mainly obtained by the pyrolysis of the transition metal, carbon and nitrogen sources together and these catalysts are viewed as potential alternative to the expensive platinum based catalysts(2). Pyrolysis step leads to formation of several nitrogen and transition metal based functionalities covalently embedded on the carbon surface(3). Hence, identifying the exact chemical structure of the ORR active site in the pyrolyzed catalyst remains elusive. Hence, designing a synthesis process (which includes pyrolysis) with an objective of maximizing the number of active sites is a work in progress. To avoid difficulties associated with such process, we propose a metalorganic complex capable of catalyzing ORR. As it is a molecular material, its characterization by single crystal XRD, 1H and 13C NMR unambiguously predicted the structure. In this study we report ORR on bis(2,2’-bipyridine-N,N’)carbonatocobalt(III)nitrate pentahydrate. The above said complex was immobilized on the Ketjenblack carbon and its ORR activity was measured in O2 saturated 0.1 N KOH solution (Figure (a)). This complex crystalizes in monoclinic (C 2/c) crystal structure and its crystal structure is shown in Figure (b). Figure Shows (a) the cyclic voltamograms recorded at different rotation rate in O2-saturated (solid lines) and in N2-saturated (dash line) 0.1 N KOH electrolyte and (b) crystal structure of the metalorganic complex employed in this work.