Non noble metal "earth abundant" electrocatalysts will significantly reduce the costs and make it possible to use electrochemical water splitting (electrolysis) on a very large scale. Non noble metal catalysts can be an effective replacement even if their electrochemical activities are a fraction of their noble metal counterparts. If these catalysts can be developed to an extent where their operational lifetime would become comparable to their noble metal counterparts, a large part of the problem would be solved. MnO₂ is earth abundant and well known for catalyzing oxygen evolution. A form of MnO_x cluster is known to catalyze water oxidation in photosynthesis.

            In order to understand the limitations of this catalyst under the operational conditions, it is important to study this material in situ. Electrodeposited of MnO_x on the surface of Au was studied using in situ Surface Enhanced Raman Spectroscopy (SERS) is used for tracking the structural changes of hydrous MnO_x. Significant amount of potential and electrolyte dependent material dynamics were revealed in the MnOx system. Besides in-situ study of catalyst structure, ex situ analysis of corrosion using flow cells combined with atomic emission spectroscopy was carried out alongside explicit detection of oxygen. Various kinds of electrolytes were used to evaluate the effects of cations, anions and solution pH on molecular structure and performance of MnO_x catalysts. Charge to radius ratio of alkali metal ions affected the reactivity of the oxides and was seen to influence reaction under both potentiostatic and potentiodynamic conditions with Li⁺ and (K⁺, Cs⁺) containing electrolytes showing the lowest and highest activities respectively. Strong effects on catalyst structure and performance were also seen when various anions such as perchlorate or borate were inluded in the electroytes being investigated.

References:

Qiang Gao, Chinmoy Ranjan,* Zoran Pavlovic, Raoul Blume, and Robert Schlögl. ACS Catalysis 2015, pp 7265-7275