Surface activation of Monel 400 alloy as novel electrode for hydrogen production: insights on electrocatalysis and electroactive surface area

Abstract

This work investigates Monel 400 as a non-noble metal electrocatalyst for the hydrogen evolution reaction (HER) in alkaline media, focusing on performance enhancement through electrochemical dealloying. Controlled electrocorrosion at 0.20 V and 0.45 V for different durations produced Ni-rich porous surfaces with significantly increased electrochemically active surface area (ECSA). Among the tested conditions, dealloying at 0.45 V for 60 min delivered the best performance, with overpotentials of 240 mV at −10 mA cm−2 and 389 mV at −80 mA cm−2, a Tafel slope of 105 mV dec−1, and a 20-fold increase in ECSA relative to pristine Monel. SEM and EDS revealed the formation of a hierarchical Ni ligament network with partial Cu depletion, while EIS confirmed enhanced capacitive and transport properties. The catalyst also demonstrated stable operation for 72 h. These results highlight dealloyed Monel 400 as a robust, scalable, and efficient HER catalyst for alkaline water electrolysis.