Electrochemical urea degradation and energy co-generation using palladium and iron-based catalysts

Abstract

Cyclic voltammetry and in-situ ATR-FTIR spectroscopy experiments revealed that urea oxidation occurs through both faradaic direct and indirect mechanisms. The Pd/C electrocatalyst facilitated the formation of formate and NO_x species, while Fe/C predominantly promoted formate formation via an indirect pathway, attributed to the high activity of iron in water activation. Polarization and power density curves indicated that both electrocatalysts degraded urea with simultaneous energy co-generation, showing comparable activity. Pd/C achieved a power density of 1.3 mW cm⁻², while Fe/C reached 1.1 mW cm⁻². Although Pd/C demonstrated advantages in reaction kinetics, the significantly lower cost of iron positions Fe/C as a promising alternative for practical applications, particularly in direct urea-fed fuel cell reactors. Additionally, Fe/C exhibited 50 % higher urea consumption near the open circuit potential compared to Pd/C, highlighting its potential for the development of more cost-effective and efficient fuel cell designs.