Coupling metal oxide nanoparticle catalysts for water oxidation to molecular light absorbers

Abstract

Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to achieve high efficiency. Molecular light absorbers offer flexibility in fine tuning of orbital energetics, and metal oxide nanoparticles have emerged as robust oxygen evolving catalysts. Hence, these materials choices offer a promising approach for the development of photocatalytic systems for water oxidation. However, efficient charge transfer coupling of molecular light absorbers and metal oxide nanoparticle catalysts has proven a challenge. Recent new approaches towards the efficient coupling of these components based on synthetic design improvements combined with direct spectroscopic observation and kinetic evaluation of charge transfer processes are discussed.

Artificial photosynthesis by light absorption, charge separation, and multielectron catalysis

“…68,69 MMCT units are all inorganic, heterobinuclear chromophores bridged by a µ-oxo between two transition metals. [70][71][72] These thermally robust units are embedded on the surfaces of mesoporous silica, but can conceivably be installed on any stable metal oxide with suitable precursors. They typically consist of an electron acceptor like d 0 Ti IV or Zr IV , coupled with an electron donor including Cr III , Mn II , Fe II , Co II , Cu I , and Ce III .…”

“…They typically consist of an electron acceptor like d 0 Ti IV or Zr IV , coupled with an electron donor including Cr III , Mn II , Fe II , Co II , Cu I , and Ce III . 68,69,[71][72][73][74][75][76][77][78][79][80][81][82][83] By astutely selecting the electron acceptor and donor, the redox potentials of the electron donor and acceptor can be tailored towards AP, with absorption onsets from the UV to visible regions. More comprehensive reviews have been published and only a cursory discussion about the synthesis, characterization, and reactivity studies with select MMCT units will be elaborated in this article to highlight their apt features for AP.…”

Hydrogel Network: A Dynamic Solution for Reversible Metal Ion Valence Switching

“…The enhanced coupling between different components can also be achieved through loading a heteronuclear metallic complex on rigid carriers or constructing bimetallic compounds/mixtures. For example, a series of oxo-bridged binuclear metallic complexes have been constructed on porous carriers, including mesoporous silica materials and metal–organic framework, featuring Ti or Zr as an electron acceptor and the first- or second-row transition metal as an electron donor center. − Furthermore, a polynuclear system consisting of a ZrOCo­(II) group coupled to an IrO x nanocluster catalyst as a reducing assistant was designed by Kim et al using mesoporous silica as the carrier . However, this design encounters challenges in precisely controlling both the metal density and the intermetal distance necessary for achieving the desired matching valence transformation.…”