Red mud as high-performance bifunctional electrocatalysts in alkaline media

Red mud, an industrial byproduct containing metal oxides, is typically landfilled, posing environmental hazards like soil and water contamination. This study investigated the potential of red mud as a cost-effective bifunctional electrocatalyst for oxygen evolution reaction and hydrogen evolution reaction. Red mud samples from two different geographic locations were laser-annealed onto nickel foam substrates and their electrochemical activity was systematically evaluated and compared with benchmark electrocatalysts under alkaline conditions. The results showed that, sample RM2/NF demonstrated the lowest overpotential during oxygen evolution reaction at current densities of 10, 50, and 100 mA cm⁻², followed by the sample, RM1/NF. Specifically RM1/NF required 310 mV to achieve a current density of 10 mA cm⁻², outperforming RM2/NF and benchmark IrO₂. For hydrogen evolution reaction, RM1/NF exhibited slightly higher activity than RM2/NF at lower overpotentials, needing only 125 mV to reach current density of 10 mA cm⁻². Electrochemical impedance spectroscopy measurement indicated a lower charge transfer resistance for both electrodes. Chronoamperometric measurements showed that RM1/NF had limited stability during oxygen evolution reaction while RM2/NF maintained superior stability during hydrogen evolution reaction over extended periods. The enhanced electrocatalytic performance of the RM2/NF electrode highlights the potential of red mud as an effective electrocatalyst, likely due to its rich elementalcomposition including iron, aluminum, titanium, and vanadium.