Catalytic Activity of an Iron-Based Water Oxidation Catalyst: Substrate Effects of Graphitic Electrodes

Abstract

The synthesis, characterization, and electrochemical studies of the dinuclear complex [(MeOH)Fe(Hbbpya)-μ-O-(Hbbpya)Fe(MeOH)](OTf)4 (1) (with Hbbpya = N,N-bis(2,2′-bipyrid-6-yl)amine) are described. With the help of online electrochemical mass spectrometry, the complex is demonstrated to be active as a water oxidation catalyst. Comparing the results obtained for different electrode materials shows a clear substrate influence of the electrode, as the complex shows a significantly lower catalytic overpotential on graphitic working electrodes in comparison to other electrode materials. Cyclic voltammetry experiments provide evidence that the structure of complex 1 undergoes reversible changes under high-potential conditions, regenerating the original structure of complex 1 upon returning to lower potentials. Results from electrochemical quartz crystal microbalance experiments rule out that catalysis proceeds via deposition of catalytically active material on the electrode surface.

Quantum Chemical Study of the Mechanism of Water Oxidation Catalyzed by a Heterotrinuclear Ru2Mn Complex

“…[1][2][3][4][5] During the past few decades, extraordinary efforts have been dedicated to the synthesis of manganese-based molecular complexes to mimic the structure and function of the OEC. [6][7][8][9][10] Other transition metals were also used for the synthesis of water oxidation catalysts, including Ru, [11][12][13][14][15][16][17][18][19][20][21][22][23][24] Ir, [25,26] Fe, [27][28][29][30][31] Co, [32][33][34] Ni, [35][36][37] and Cu. [38][39][40] Recently,the Llobet group disclosed the synthesisofaheterotrinuclear Ru 2 Mn complex A 0 {[Ru II (tpy)] 2 (m-[Mn II (bpp) 2 ]) (OAc) 2 } 2 + [tpy = 2,2':6',2''-terpyridine, bpp = 3,5-bis(2-pyridyl)pyrazolate].…”

Iron‐Based Molecular Water Oxidation Catalysts: Abundant, Cheap, and Promising

“…Asian J. 2019,14,[31][32][33][34][35][36][37][38][39][40][41][42][43] www.chemasianj.org reported as WOCs. For example, Thummel and co-workersr eported a m-oxo-bridgedd inuclear complex (53), with a 2-(pyrid-2'-yl)-8-(1'',10''-phenanthrolin-2''-yl)quinoline (ppq) ligand,a nd am ononuclear counterpart( 52), with ab is-phenanthroline amine (dpa) ligand,s haring similars quare-planar arrangement of the quaterpyridine-like backbone (Figure 11).…”

“…[43] The possibility of forming the metal oxide on the surface of the electrodea st he true catalytic site could be precluded from the resultso fe lectrochemical quartz crystal microbalance experiments;t hus providing evidencef or the molecular nature of the catalytically active species. [43] Notably,t he possible influence of the electrode materialm ust be considered when benchmarking WOCs. This binuclear complexs howed an onset potential, in the case of graphitic workinge lectrodes, that was significantly lower than that obtained in experiments with a gold workinge lectrode;t hus demonstrating ac lear influence of the substrate of the electrode material on the catalytic performance.…”

The Middle‐Earth between Homogeneous and Heterogeneous Catalysis in Water Oxidation with Iridium

“…Nevertheless, WOCs have to interact with the anode in order to be oxidized and the chemical nature of the material constituting anode might play a critical role on the efficiency of the process. As a matter of fact, examples showing the dependence of WOC activity on the nature of the anode have been reported in the literature . Finally, also in photocatalytic experiments, after light absorption by the antenna system and photoinduced charge separation, an oxidant species is generated that has to transfer its oxidative power to the catalyst, which in turn oxidizes water.…”