Water Electrolysis with a Homogeneous Catalyst in an Electrochemical Cell

Abstract

[Ru(Mebimpy)(bpy)OH2]2+[Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2′-bipyridine], a homogeneous molecular catalyst for water oxidation, is examined using an electrochemical flow cell. A homogeneous catalyst can reduce corrosion by operating at near-neutral pH and is easy to replace when degraded. Traditional alkaline electrolyzers are not free of these issues. The electrochemical flow cell, which is based on a fuel-cell design, includes a zero-gap configuration to minimize ohmic losses. The homogeneous-catalyst kinetics is elucidated by means of electrochemical methods, including Tafel plots. Current efficiencies are measured from the evolved gases. Relationships between catalyst performance and concentration, anode material, and electrolyte conductivity and pH are discussed. Changes in electrolyte pH caused by electrolysis conditions are also presented.