Electrochemical-driven water reduction and oxidation catalyzed by an iron(III) complex supported by a N2O2 ligand

Abstract

One new electrocatalyst for both water reduction and oxidation, based on an iron(III) complex, FeIII(TAMP)Cl, is formed by the reaction of anhydrous FeCl3 with thiobis(2,1-phenylene)-bis(azanylyidene)-bis(methanylylidene)-bis-phenol (H2TAMP). Its structure has been determined by X-ray diffraction. A Bond-Valence Sum (BVS) model calculation was performed to assign the oxidation state of the iron center in FeIII(TAMP)Cl. FeIII(TAMP)Cl can electrocatalyze hydrogen evolution from a neutral electrolyte solution (pH 7.0) with a turnover frequency (TOF) of 2.43 mol of hydrogen per mole of catalyst per second (mol (mol cat)−1s−1) at an overpotential (OP) of 837 mV. Water oxidation occurs at an overpotential of 791 mV to give O2 with a TOF of ∼124.06 mol O2 (mol cat)−1s−1. Sustained proton reduction catalysis occurs at glassy carbon to afford H2 over a 5 h electrolysis period with 92% Faradaic yield and no observable decomposition of FeIII(TAMP)Cl. We hope these findings can afford a new method for the design of electrocatalysts for both water reduction and oxidation.