Oxygen-evolution Reaction by Silicate Stabilized Manganese Oxide

Oxygen-evolution reaction (OER) through water oxidation under acidic conditions mediatedby efficient and stable first-row transition metal compounds remains a challenge in artificialphotosynthesis [۱,۲]. A critical issue in the field is the solubility of first-row transition metalcompounds during OER and under acidic conditions. In this study, the silicate-stabilized Mnoxide was investigated for OER under acidic conditions (pH < ۱). Compared to Mn oxide, thesilicate-stabilized Mn oxide is significantly more stable than Mn oxide under acidic conditions(pH < ۱), with the overpotential of ۴۵۷ mV for the onset of OER. The Mn oxides forming in theabsence and presence of silicate groups are α-Mn۲O۳ and α-MnO۲, respectively. For the Mnoxides forming in the presence of silicate groups, the corresponding current densities of ۱ and ۱۰mA/cm۲ are recorded at ۵۲۷ and ۶۴۰ mV, respectively. Silicate-stabilized Mn oxide wascharacterized by a number of methods before and after OER. The ۲۹Si NMR spectrum forsilicate-stabilized Mn oxide shows that the Si-O groups chemically bonded to Mn ions. Thescanning transmission electron microscopy shows small ۲ – ۱۰ nm particles of Si-O compoundin silicate-stabilized Mn oxide. Especially, Si-O to stabilize the higher indices facets of the Mnoxide crystallites. X-ray absorption spectroscopy confirms that the predominant structure forsilicate-stabilized manganese oxide is α-MnO۲, with di- and mono-μ-oxo-bridged Mn atoms.After prolonged oxygen evolution, a certain fraction of the mono-μ-oxo bridges disappear forsilicate-stabilized manganese oxide. Adding silicate to Mn oxide is a low-cost andenvironmentally friendly procedure to increase the stability of Mn oxide toward OER underacidic conditions, thus our procedure is a clear improvement on current methods to stabilize Mnoxide for OER under acidic conditions

کلیدواژه ها:

Acidic conditions ، catalyst ، oxygen-evolution reaction ، silicate stabilized manganeseoxide ، stability