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Catalytic Water Oxidation with Immobilized Iridium Complexes

Immobilized and Heterogenized Iridium Complex on a Conductive Substrate, Used in Oxygen Evolution Reactions

The development of technologies related to the production of carbon-free chemical fuels is a driving force toward a new and sustainable energy ecosystem. Electrochemical or catalytic water splitting has been attracting research interest due to its ability to provide clean and renewable hydrogen fuel with minimum carbon emission. Water splitting consists of two half-cell reactions: the reduction – reaction involving the hydrogen evolution reaction (HER) (2H+ + 2e → H2) and the oxidation – reaction involving oxygen evolution reaction (OER) (2H2O → O2 + 4H+ + 4e).  Each of these reactions requires a catalyst for the reaction to take place at a reasonable rate. However, of the two reactions, the oxidation step is the main obstacle limiting the efficiency of overall water splitting due to the slow four-electron transfer rate and the high activation energy barrier for O–O bond formation.[1]

Strem Chemicals, in collaboration with Catalytic Innovations, LLC, offers Iridium (77-0025; 77-0030; 77-0035; 77-0040) and Cobalt (27-0477) based water oxidation catalysts.

[2-(Pyridine-2-yl)-2-propanato]iridium(IV) dimer solution (77-0025) is a homogenous molecular catalyst that allows heterogenization to form a surface-bound, ligand-modified, iridium electrocatalyst for water oxidation in acidic solutions. By self-adhering to the surface of a metal oxide at room temperature, a molecular monolayer of the catalyst is formed, which exhibits higher activity than the bulk material analogue, IrOx. The ligand 2-(pyridine-2-yl)propan-2-ol, pyalc (07-3333), a tertiary pyridyl alcohol, has a high resistance to oxidation that promotes metal-centered oxidation and stabilization of the Ir(IV) oxidation state.[2-6]

image 1

Heterogenization of the material can be performed in air, at ambient temperature, with no additives, but applied potential or other treatment is required. This process is applicable for most carbon-based or metal oxide substrates.  For a more detailed standard operating procedure please refer to the technical note for 77-0025.  Alternatively, Strem also offers acid-stable ATO (Antimony Tin Oxide) conductive substrates that are already decorated iridium catalysts: 77-0030 (20nm); 77-0035 (50nm); 77-0040 (100nm).

Cobalt-dppe (27-0477) heterogeneous water oxidation catalyst is noteworthy mainly because of its selectivity.  In contrast to the heterogenized molecular iridium catalysts, it is a purely heterogeneous catalyst. This light-brown nanopowder is prepared by thermolysis of dicobalt octacarbonyl (27-0400) in the presence of the bidentate phosphine ligand 1,2-bis(diphenylphosphino)ethane (15-0200).[7] The Co-dppe catalyst is highly selective for the oxidation of water in the presence of high concentrations of chloride, whereas the more conventional Co3O4 (93-2712) catalyst is known to be unselective for the oxidation of water over the oxidation of chloride.

If you are interested in reading more about these products and processes please see the article in our most recent Chemiker publication, "Heterogenized Molecular Iridium Complexes for Catalytic Water Oxidation and C-H Activation".   We also have a brief literature sheet available for viewing and download titled Complexes for Catalytic Water Oxidation.


  1.       Chem. Rev. 2015, 115, 12974
  2.       J. Am. Chem. Soc., 2013, 135, 10837.
  3.       J. Am. Chem. Soc., 2014, 136, 13826.
  4.       Nat. Commun., 2015, 6, 6469.
  5.       Angew. Chem. Int. Ed., 2015, 54, 11428.
  6.       Energy Environ. Sci., 2016, 9, 1794.
  7.       US Patent Publication No. US20150065339 A1


Products mentioned in this blog and related products:

07-3333: 2-(Pyridine-2-yl)propan-2-ol, min. 95% pyalc, [37988-38-8]

15-0200: 1,2-Bis(diphenylphosphino)ethane, 99% DIPHOS, [1663-45-2]

27-0400: Cobalt carbonyl (Dicobalt octacarbonyl) (Stabilized with 1-5% hexanes) [10210-68-1]

27-0477: Cobalt-dppe heterogeneous water oxidation catalyst (~17%-Co)

27-3015: Triethylammonium {chlorobis(dimethylglyoximato)(4-hydrogenphosphonatepyridinyl) cobaltate(III)} [1280199-86-1]

28-1720: Bis{P,P'-1,5-diphenyl-3,7-bis[(4-hydrogenphosphonate)phenyl]-1,5,3,7-diazadiphosphocine} nickel(II) bromide (hydrogen bromide adduct) [1514896-39-9]

77-0025: [2-(Pyridine-2-yl)-2-propanato]iridium(IV) dimer solution 97% (1 mM in 0.1 Molar aqueous NaIO3) [1446713-81-0]

77-0030: Antimony Tin Oxide/Iridium Het-WOC core/shell nanopowder, 20 nm (conductive and acid-stable)

77-0035: Antimony Tin Oxide/Iridium Het-WOC core/shell nanopowder, 50 nm (conductive and acid-stable)

77-0040: Antimony Tin Oxide/Iridium Het-WOC core/shell nanopowder, 100 nm (conductive and acid-stable)

93-2712: Cobalt(II,III) oxide, 99.5% [1308-06-1]



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