Manganese Carbonate (Mn₂(CO₃)₃) as an Efficient, Stable Heterogeneous Electrocatalyst for the Oxygen Evolution Reaction

With the growing population and energy demand, there is an urgent need for the production and storage of clean energy obtained from renewable resources. Water splitting electrocatalytically is a major approach to obtain clean H2. The efficiency, stability, and slow kinetics of anode materials developed so far do not fit the commercial application of the water oxidation reaction. To develop an efficient energy conversion catalyst, particularly for the oxygen evolution reaction (OER) herewith, Mn2(CO3)3 was electrodeposited on a Ni foam (NF) electrode surface by the chronoamperometric technique. The deposited Mn2(CO3)3/NF was characterized using various surface characterization techniques. The electrochemical behavior of the Mn2(CO3)3/NF-deposited electrode toward the OER was studied using electrochemical methods in KOH (pH 14) and NaHCO3 (pH 8.3) electrolytes. The Mn2(CO3)3/NF electrode showed a lower overpotential than CO3/NF and NF electrodes in the KOH/NaHCO3 media. The Mn2(CO3)3/NF electrode performs high electrocatalytic water oxidation with an overpotential of 360 mV at a current density of 10 mA·cm–2. This overpotential is much lower than those of CO3/NF (460 mV) and bare NF (520 mV), with good long-term stability in the KOH medium without any catalytic degradation after 100 CV cycles and 15 h chronoamperometric studies. The stability of the electrodeposited Mn2(CO3)3 on the NF electrode was determined by X-ray photoelectron spectroscopy. Thus, the Mn2(CO3)3/NF catalyst is suitable for the oxygen evolution reaction

Sacrificial Oxidants as a Means to Study the Catalytic Activity of Water Oxidation Catalysts

An overview of the different sacrificial oxidants used in literature is reported, paying particular attention to the “sacrificial pair”, a photosystem made of a Ru-dye (Tris(bipyridine)ruthenium(II) dichloride, working as “antenna” for visible light) and a final electron acceptor (i.e. the persulfate ion). Such sacrificial oxidant is one of the most common in the literature and it was used in all the experiments described in Chap. 4. Different configurations of batch reactors can be used in the sacrificial-oxidant-driven water oxidation (WO) reaction, and three of them (i.e. the Clark-electrode Cell, the Stripping Flow Reactor and the Bubbling Reactor) are described in detail. The effects of both mass transfer limitations and side reactions on the determination of the two parameters describing the activity of water oxidation catalysts (i.e. the O2 production rate and the total evolved O2) are discussed, evidencing how such undesired phenomena occur to a different extent with the three reactor configurations