Domestic wastewater treatment using Pt,Ni-RE (rare earth) electrodes

Electrochemical technologies can be used for the treatment of domestic wastewaters, by eliminating their organic pollutants. They have advantages over conventional methods, such as environmental compatibility, versatility, energy efficiency, safety and cost. The organic compounds degradation process is based on the production of OH radicals, formed during water electrolysis, which oxidize the organic molecules to CO2. At the same time, hydrogen (H-2) is produced through reduction of the water in the effluent, which can be later used in a fuel cell. Present study seeks to find effective electrocatalysts to produce H-2 by electrolysis, using domestic wastewaters as the hydrogen source, with or without the addition of supporting electrolyte. Herein KOH is used as the supporting electrolyte, as the extra hydroxide can be used to degrade the organic matter. Nine different electrode materials are evaluated as cathodes for the hydrogen evolution reaction (HER) in a domestic wastewater. The tested materials include platinum (Pt) and platinum-rare earth (Pt-RE) binary alloys, and nickel (Ni) and Ni-RE alloys, with the REs being cerium (Ce), samarium (Sm), dysprosium (Dy), and holmium (Ho). Linear scan voltammetry measurements are conducted at temperatures ranging from 25 to 85 degrees C. Several kinetic parameters are calculated, such as the Tafel slopes, charge transfer coefficients and exchange current densities. The data obtained at the different electrode materials is compared and it is clear that Pt-RE alloys show superior activity for the HER. It is also noticeable that the wastewater effluent containing the supporting electrolyte leads to significantly better HER performances.