Nanolayered manganese oxide/poly(4-vinylpyridine) as a biomimetic and very efficient water oxidizing catalyst: toward an artificial enzyme in artificial photosynthesis

Abstract

Nanolayered Mn oxide/poly(4-vinylpyridine) as a model for Mn cluster in photosystem II was synthesized and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy (UV-Vis). The compound is a very efficient water oxidizing catalyst, and sizable oxygen evolution was detected at 50 mV overpotential at near neutral pH. The number is as low as the overpotential is used by nature in photosystem II of cyanobacteria, algae and green plants for similar reactions.

From manganese complexes to nano-sized manganese oxides as water-oxidizing catalysts for artificial photosynthetic systems: Insights from the Zanjan team

“…3), and another mechanism is related to the attack of an outer-sphere water molecule on an OH group that is coordinated to a high-valent Mn ion in the oxide phase (pathway i in Fig. 3) [47,48]. Interestingly, we observed these two ranges for water oxidation for nano-layered Mn oxides, at least, at pH ¼ 6.3 [48].…”

“…Interestingly, we observed these two ranges for water oxidation for nano-layered Mn oxides, at least, at pH ¼ 6.3 [48]. The first range for water oxidation is near to the peak related to the Mn(III)/Mn(IV) couple with 50e250 mV overpotential, and another one has 600e1000 mV overpotential for water oxidation [48]. We relate these points to pathways ii and i in Fig.…”

“…Reprinted with permission and modification from Ref. [48]. Copyright (2013) by The Royal Society of Chemistry.…”

“…Our group used the strategy of inserting nano-sized Mn oxides into organic polymer/poly peptides [48,98e100]. We reported on a nanolayered Mn oxide/poly(4-vinylpyridine) as a model for an Mn cluster in PSII [48].…”

Manganese oxides supported on gold nanoparticles: new findings and current controversies for the role of gold

“…Such materials show higher activities toward water oxidation compared with gold nanoparticles or nanolayered Mn oxide. The use of organic compounds in the procedure of gold reduction may cause the formation of some Mn(III) ions on the surface of oxide and thus increase the water oxidation activity of Mn oxide (Takashima et al 2012;Najafpour et al 2013a). However, it was proposed that gold may also facilitate the transfer of electronic charge to Mn oxides (Najafpour et al 2013e).…”