Performance Enhancement for Electrolytic Systems through the Application of a Cobalt-based Heterogeneous Water Oxidation Catalyst

We report a heterogeneous cobalt−phosphine-based water oxidation catalyst that was produced by thermal synthesis, and can be easily and rapidly deposited onto a variety of substrates from a suspension. Application of the catalyst dramatically improved the oxygen evolution efficiency and corrosion-resistance of stainless steel, nickel and copper anodes in alkaline media. More than 20 g of catalyst was prepared in a single batch, and it was shown to be effective at surface loadings as low as 20μg/cm2. The catalyst was investigated in three different systems: (1) An alkaline electrolyzer with stainless steel electrodes activated with the catalyst supported 120−200% of the current density of an unactivated but otherwise identical electrolyzer, over a range of applied potentials, and maintained this improved efficiency throughout 1495 h of continuous use in 1 M NaOH. (2) Copper anodes were activated and protected from corrosion in dilute sodium hydroxide for 8 h of electrolysis, before a steady decrease in performance over the next 48 h. (3) Activation of nickel anodes with the catalyst reduced the required overpotential by 90−130 mV at current densities between 7.5 and 15 mA/cm2, thereby increasing the cell efficiency of water splitting as well as zinc deposition from alkaline zincate electrolytes. The cell efficiency for zinc deposition at a current density of 12.5 mA/cm2 was improved from 68.0% with a nickel anode to 72.0% with 50μg/cm2 catalyst on the nickel anode.