Artificial photosynthesis (AP), the conversion of water and sunlight into fuel, is an attractive approach for addressing the intermittent nature of solar energy. The oxygen evolving half reaction (OER) is considered to be the limiting factor in the efficiency of an AP device due to the kinetic challenge of coupling 4 H+ with 4 e−, and forming an O−O bond. While numerous OER catalysts exist, their composition from rare metals or mild activity limits their utility in an AP device. To improve catalysis, a better mechanistic understanding is required and molecular models may be used for this purpose. Recent mechanistic studies of a Co(III)4O4 cubane as a molecular model of CoOx implicate the involvement of terminal Co(V) and Co(IV) oxo centers. This finding suggests that improved activity and stability may be achieved by doping the catalyst with a metal that more readily forms high valent oxos. Indeed, Mn-doped Co(OH)x materials exhibit superior activity compared to CoOx, though thorough mechanistic studies are lacking. To investigate the effect of Mn-doping on a catalyst's OER activity, we performed electrochemical studies of a Mn-doped Co(III)4O4 cubane. The mechanistic understanding provided by these studies may elucidate the role of Mn both in synthetic catalysts and in natural photosynthesis, and should facilitate the development of improved OER catalysts.

Mechanistic investigations of oxygen evolution at a manganese-doped cobalt cubane catalyst

253rd National Meeting (2017)

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