دانلود رایگان مقاله افزایش اکسیژن خالی ناشی از اکسیداسیون آب فتوشیمیایی در کاتالیزور کلسیم اکسید منگنز

1. Introduction

The photo(electro)chemical splitting water into hydrogen and oxygen has attracted tremendous attention in recent years because of its great potential in solar energy conversion and storage applications [1]. In respect to hydrogen evolution reaction, a two-electron-transfer process, oxygen evolution reaction is more complex, which involves fourelectron-transfer process. Currently, owing to the slow four-electron transfer rate and the high activation energy barrier for O\\O bond formation, the oxygen evolution is the main obstacle limiting the efficiency of overall water splitting [2]. Searching environmentally-friendly and efficient oxygen evolution catalysts (OECs) is an urgent and challenging task among the solar water splitting community. In nature, a Mn4CaO5 cluster as the oxygen evolving complex in photosystem II (PS II), has been identified as the catalytic site for the fourelectron involved water oxidation [3]. Inspired by the natural photosynthesis process in PS II, synthetic manganese-containing compounds are thought to be very promising candidates as functional water oxidation catalysts to mimic the role of Mn4CaO5 cluster in water oxidation [4]. Various nanostructured solid manganese oxides (MnOx) including MnO2, Mn2O3, Mn3O4, MnOx, MnO, Mn3(PO4)2·3H2O, CaMn2O4·xH2O and amorphous CaxMnOy have been synthesized and tested as OECs in either electrochemical or photochemical systems [5–12].

4. Conclusions

In summary, Ca2Mn2O5 as a biomimetic water oxidation catalyst was evaluated in both photochemical and electrochemical systems. The increased structural distortion arising from oxygen vacancies in Ca2Mn2O5 would be beneficial for adsorption of OH– ions onto the oxygen vacant site on MnO5 subunit, which was proposed as the main reason to improve its water oxidation performance in comparison with CaMnO3 and MnO2. Further structural modification of the calcium manganese oxides is suggested to improve their stabilities.