Urea electrolysis in alkaline media remediates urine-rich wastewater and prevents gaseous ammonia emissions and nitrate contamination of ground and drinking water that currently results when purged to rivers and lakes untreated. Pure hydrogen is evolved at the cathode and easily collected for use as a valuable fuel. Scaling this technology to industrial applications such as wastewater treatment plants and farms could prevent health problems and costs due to toxic emissions and support the emerging hydrogen economy. However, several obstacles must be overcome before scale-up is feasible. Aqueous KOH electrolyte currently used for alkalinity requires either continual addition to the process stream or separation and recycling steps, both of which present an economic disadvantage. Also, although inexpensive nickel catalyst is favorable in terms of current density this catalyst thus far has not sustained stable current due to deactivation of the nickel surface.
To overcome these hurdles a poly(acrylic acid) (PAA) gel electrolyte was investigated with various KOH concentrations and polymer weight percents. It was found that a composition of 8 M KOH and 15 wt % PAA is a feasible substitute for aqueous KOH electrolyte, providing similar conductivities of 0.9 S/cm as compared to 0.58 S/cm for 1 M aqueous KOH. The gel electrolyte retains a small volume of KOH in its polymer matrix directly between the electrodes. Therefore, implementing this gel electrolyte in the system eliminates the need for aqueous KOH input or recovery steps. In addition various platinum group metals (Pt, Pt-Ir, Rh, and Ru) were deposited on nickel substrate to determine which combination could stabilize current density and prevent nickel deactivation. Rh-Ni electrodes proved to both enhance current density and stability compared to other metal combinations or nickel alone.