Influence of the thermal synthesis method on the structure and electrocatalytic behavior of Ti/(RuO2)x(Mn3O4)1-x catalysts applied to acidic water oxidation

The development of efficient and durable electrocatalysts for the oxygen evolution reaction (OER) is essential for advancing large-scale water electrolysis, particularly in acidic media and real seawater. In this work, Ti/(RuO 2 ) x (Mn 3 O 4 ) 1- x materials with distinct amounts of Ru and Mn were synthesized via the Pechini method and subjected to three distinct heating treatments named conventional furnace, hybrid microwave, and CO₂ laser, aiming to evaluate the influence of thermal processing on their structural and electrocatalytic properties. Regardless of the heating method, it was possible to assign diffraction peaks for RuO 2 and Mn 3 O 4 phases. However, scanning electron microscopy revealed that faster heating approaches produced more compact and homogeneous surfaces, reducing crack formation compared to conventional heating. The heating method strongly impacts electrochemical activity, in which thermal treatment in both microwave and CO 2 laser produces more active materials (lower overpotential and lower Tafel slopes) for OER compared to a conventional furnace. Microwave-treated materials presented the highest electrochemically active surface area, whereas laser-treated anodes exhibited the lowest charge transfer resistance as evaluated by electrochemical impedance spectroscopy, resulting in superior intrinsic activity. Moreover, long-term electrolysis tests in both acidic real seawater electrolytes demonstrated stable performance of Ti/(RuO 2 ) 0.5 (Mn 3 O 4 ) 0.5 electrode prepared in the microwave. After 90 h at 10 mA cm −2 in acidic media, both XPS and SEM/EDS analyses revealed morphological changes with Mn lixiviation. Overall, the results highlight that rapid and energy-efficient heating methods are highly effective for tailoring RuO 2 -Mn 3 O 4 mixed oxides, offering a promising route to produce low-cost, stable, and high-performance anodes for sustainable hydrogen generation.