• Scalable electrodeposition yields Ni/MXene and Ni/Mo₂C composites with enhanced HER performance. • Carbides and MXenes reshape Ni into high-area, high-activity interfaces for alkaline electrolysis. • DEMS enable reliable HER onset detection and clarify the rate-determining step. • Composites outperform Ni cathodes in activity, charge transfer, and stability for low-cost alkaline electrolyzers. • Ni/Mo₂C shows the fastest charge-transfer kinetics (lowest R ct ), while Ni/Mo₂TiC₂ offers the best activity–stability balance. Nickel-based catalysts are promising alternatives to noble metals for hydrogen evolution in alkaline media; however, their long-term stability and scalability remain a challenge. In this paper, we report the synthesis of nickel composites with laboratory-synthesized molybdenum carbide (Mo₂C) and MXenes (Ti₃C₂ and Mo₂TiC₂) via electrodeposition, a cost-effective and industrially scalable method compatible with the fabrication of alkaline water electrolysis (AWE) electrodes. The catalysts were systematically characterized by SEM/EDX, DRX, EIS, cyclic voltammetry, chronoamperometry, and, notably, differential electrochemical mass spectrometry (DEMS). DEMS enabled real-time quantification of hydrogen evolution, providing mechanistic insights beyond conventional electrochemical techniques. The Ni/Mo₂C composite exhibited the lowest charge-transfer resistance and superior intrinsic activity, whereas Ni/MXene electrodes demonstrated higher electrochemically accessible surface areas and improved stability. Overall, this work highlights electrodeposition as a versatile strategy for preparing advanced Ni-based composites and underscores the value of DEMS in elucidating the hydrogen evolution mechanism in noble-metal-free systems

• Filtration maximizes •OH production by activating the full electrode area. • Flow-through behavior shifts the oxygen evolution potential anodically. • Flow-through mode is the optimal operation condition for EF. • Flow-by mode loses over 70% of the active area at high flow rates. Electrofiltration is an emerging electrochemical technique that enables simultaneous filtration and advanced oxidation for water treatment, offering improved control over mass transport and surface activation compared with conventional electrochemical process. Ceramic 3D Sb-doped SnO 2 porous electrodes have been proven to be suitable electrofiltration anodes. In this work, the impact of hydrodynamics on the electrochemical behavior and oxidizing capability of such electrofiltration anodes was investigated. Cyclic voltammetry revealed that, without filtration, the system behaves as a quasi-2D flow-by electrode with low internal resistance, limited electroactive area and low oxygen evolution potential at high injection flow. Under filtration, the system behaves as a 3D flow-through electrode exhibits a higher ohmic resistance for all the tested flow rates, an anodic shift of the oxygen evolution potential and a higher activated area. The ability to generate hydroxyl radicals was assessed by salicylic acid electrofiltration and quantification of 2,5- dihydroxybenzoic acid and 2,3-dihydroxybenzoic acid, confirming that hydroxyl radical production at 20 L/h is effective both, without filtration and with filtration; whereas at 60 L/h it is strongly hindered in flow-by mode and only partially recovered under flow-through operation. These findings highlight the critical role of hydrodynamics in electrofiltration with porous ceramic Sb–SnO₂ anodes and provide a mechanistic link between flow regime, electrochemical response and radical-mediated oxidation performance.

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.