Polyoxometalate Multielectron Catalysts in Solar Fuel Production

Multi-Tasking POM Systems

“…One of the primary applications that has been the subject of extensive research within the field of POMs has been the catalysis of water oxidation. Since the original reports of a POM water oxidation catalyst (WOC), namely the tetra-ruthenium sandwich polytungstate, [{Ru 4 O 4 (OH) 2 (H 2 O) 4 }(γ-SiW 10 O 36 ) 2 ] 10− (Ru 4 Si 2 )(Geletii et al, 2008 ; Sartorel et al, 2008 ), and the first publication on a POM WOC of all earth-abundant elements (Yin et al, 2010 ), there have been scores of papers on POM WOCs (Lauinger et al, 2017b ; Li J. et al, 2017 ).…”

“…Polyoxometalate WOCs have been of particular concern in this regard (Stracke and Finke, 2011 , 2014 ; Vickers et al, 2013 ; Folkman and Finke, 2017 ). This is due to the fact that POMs are essentially molecular metal oxides and could potentially have extensive speciation equilibria in solution (Sumliner et al, 2014 ; Sara et al, 2015 ; Lauinger et al, 2017b ; Nyman, 2017 ). Some of the species that could be present include the metal aqua complexes as well as the corresponding metal oxide nanoparticles, all of which could also be active as WOCs (Stracke and Finke, 2014 ; Sumliner et al, 2014 ; Folkman and Finke, 2017 ; Lauinger et al, 2017b ; Suen et al, 2017 ).…”

“…This is due to the fact that POMs are essentially molecular metal oxides and could potentially have extensive speciation equilibria in solution (Sumliner et al, 2014 ; Sara et al, 2015 ; Lauinger et al, 2017b ; Nyman, 2017 ). Some of the species that could be present include the metal aqua complexes as well as the corresponding metal oxide nanoparticles, all of which could also be active as WOCs (Stracke and Finke, 2014 ; Sumliner et al, 2014 ; Folkman and Finke, 2017 ; Lauinger et al, 2017b ; Suen et al, 2017 ). It is therefore essential that any POM species is demonstrated to be stable and active under experimental conditions.…”

“…POMs have been immobilized on photoanodes to make photocatalytic water oxidizing electrodes, allowing careful tailoring of POMs during their synthesis to be combined with the stabilizing effects of a heterogeneous material. Heterogeneous systems involving POMs are generally more stable than their molecular counterparts due to the limiting of solution phase equilibria involving the POM, preventing speciation that could lead to a shift in the composition of the catalytic POM cluster (Lauinger et al, 2017b ). Heterogeneous WOCs are also advantageous because both half reactions involved in water splitting are spatially separated, preventing product recombination or the collection of an explosive mixture of hydrogen and oxygen.…”

Immobilization of molecular catalysts for artificial photosynthesis

“…The concept of storing the solar energy into higherenergy chemicals is the basis of artificial photosynthesis, which is dedicated to producing fuels/high-value chemicals such as H 2 , methane, methanol, or hydrogen peroxide. A number of molecular catalysts have been developed for water splitting [3][4][5][6][7][8][9][10][11][12], CO 2 reduction [13][14][15][16][17][18][19][20][21], and O 2 reduction [22,23]. However, the molecular catalysts in homogeneous solution often suffer from low stability in redox conditions.…”