A green approach to transition metal-based nanoparticles from aluminium powder cementation for application in OER electrocatalysis

Anion-exchange-membrane water electrolyzers (AEMWEs) represent a highly promising technology for hydrogen production using renewable energy sources. To enable the broad implementation of AEMWEs, it is crucial to improve simple, scalable and environmentally friendly synthetic methods for the development of transition metal-based electrocatalysts. Here, FeCo3/FeCoOx and Ni1-xCox/NiCoOx nanoparticles were obtained via a feasible two-step synthesis in an aqueous solution by cementation of aluminium powder. Both materials were tested as oxygen evolution reaction (OER) electrocatalysts comparing the electrochemical performance with commercial benchmark RuO2. The FeCo3/FeCoOx and Ni1-xCox/NiCoOx exhibited overpotentials of 288 mV and 296 mV, respectively, for OER at a current density of 10 mA cm⁻², allowing a comparison between mass activity and geometric activity with RuO2. When integrated as anode electrocatalyst into a pilot-scale AEMWE, the materials were able to reach 2.10 V and 2.24 V (without iR-correction) at a current density of 1 A cm−2 (50 °C), respectively. After acquiring the polarization curves, the AEMWE tests were extended for 100 h with a continuous power profile, to have an initial assessment of ​​the possible degradation trends for a future industrial application. The degradation rate resulted in 396 µV h−1 in the case of FeCo3/FeCoOx and no significant degradation for Ni1-xCox/NiCoOx. This study presents a straightforward and scalable approach to synthesizing earth-abundant electrocatalytic materials designed for high-efficiency OER.