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

Abstract

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 20 μg/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 50 μg/cm2 catalyst on the nickel anode.