Low-Cost Bipolar Plates of Ti(4)O(7)-Coated Ti for Water Electrolysis with Polymer Electrolyte Membranes

[Image: see text] Although hydrogen is expected to play an important role in the storage of energy from renewable energy sources, technology to produce hydrogen at low cost is needed for its widespread use. The key to the low-cost production of hydrogen with a polymer electrolyte membrane (PEM) water electrolysis system, which is widely used today, is to replace the Au- or Pt-coated Ti with a low-cost material that can be manufactured from inexpensive, corrosion-resistant, and conductive components. We studied titanium suboxide (Ti(4)O(7))-coated titanium (Ti) bipolar plates, which can be substituted for commonly used Pt-coated Ti bipolar plates, as an inexpensive way of producing the PEM water electrolysis system. The water electrolysis characteristics of the cell were evaluated using Ti(4)O(7)-sputtered Ti for the bipolar plates of the water electrolysis cell, and the applicability of Ti(4)O(7)-sputtered Ti was investigated. The Ti(4)O(7)-sputtered Ti had a very low contact resistance (4–5 mΩ cm(2)) before and after voltage application that was equivalent to that of gold or platinum plating. The efficiency of water electrolysis in this study was comparable to those of previous reports using bipolar plates coated with precious metals. This development opens the door for fabrication of low-cost electrolyzers as well as related electrochemical devices such as fuel cells, sensors, catalysts, and air or liquid cleaning devices.