Oxygen Evolution Enhancement of Nickel (Hydr)Oxide via Iron Coordination Compound in Alkaline Conditions

This study investigates the complex dynamics of the oxygen-evolution reaction (OER) in systems involving Ni(Fe) (hydr)oxides and the iron coordination compound Fe phthalocyanine-4,4',4″,4‴-tetrasulfonate. It offers a novel perspective on the interaction between nickel hydroxide and the Fe compound during the OER process. The Fe complex facilitates the controlled release of trace Fe ions into the Ni (hydr)oxides as it undergoes degradation or demetalation within the Ni(II)/(III) potential range. Once the electrode surface reaches saturation with Fe, additional contributions from Fe have minimal impact on OER activity, and the turnover frequency rapidly reaches its maximum value (approximately 1 s^-1) under cyclic voltammetry. In situ Raman spectroscopy reveals that the interaction between the iron complex and the electrode surface, as well as the amount of complex deposited or adsorbed, depends on the applied potential of the electrode. Changes in the electrode's potential influence how the Fe complex binds to the surface, through mechanisms such as electrostatic attraction, chemical bonding, or other interactions. This underscores the critical role of potential control in optimizing electrode surface modifications and enhancing the efficiency of electrochemical processes involving the iron complex.