ENHANCED H2 PRODUCTION IN SUBSURFACE AND ABOVE GROUND ENVIRONMENTS IN THE PRESENCE OF SPINEL OXIDES
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The generation of hydrogen through geological processes such as serpentinization holds significant promise for advancing sustainable energy solutions. In this study, we explore the enhancement of hydrogen evolution by developing nickel-doped ferrite catalysts, drawing inspiration from natural geological phenomena. Serpentinization, a process occurring in ultramafic rocks, involves the oxidation of Fe(II) to Fe(III) and the reduction of water to hydrogen, though these reactions are often slow and poorly understood at low temperatures and pressures. Our research aims to replicate and optimize these reactions through the synthesis of spinel ferrites with improved catalytic performance.Two distinct nickel-doped ferrite catalysts were synthesized using a hydrothermal method, one from nitrates and another from chlorides of iron and nickel. The first synthesis, using ferric and nickel nitrates, involved a urea-mediated spinel formation at 110°C, while the second synthesis utilized ferrous chloride, enabling direct oxidation from Fe(II) to Fe(III). Our results demonstrate that the chloride-based catalyst exhibited superior morphology, surface area, and catalytic performance due to the elimination of NaOH, which often compromises spinel structures. Through systematic experimentation, we show that the introduction of nickel into the spinel structure significantly enhances hydrogen production. The ferrite catalyst synthesized with ferrous chloride exhibited a 200-fold increase in hydrogen evolution compared to the base case with pure iron salts, and over a 450-fold increase when tested in an olivine leachate environment. X-ray photoelectron spectroscopy (XPS) confirmed the presence of mixed oxidation states of Fe (Fe²⁺/Fe³⁺) and Ni (Ni²⁺/Ni³⁺), which are critical for redox cycling and catalytic activity. These findings align with previous literature indicating that mixed valency enhances the kinetics of water reduction and hydrogen evolution. Our work contributes to the broader understanding of hydrogen generation under geologically relevant conditions and offers insights into designing efficient catalysts for hydrogen production. By replicating and optimizing natural water-rock reactions, this research provides a pathway toward sustainable hydrogen production, advancing efforts to decarbonize energy systems and reduce greenhouse gas emissions. The results have implications not only for geological hydrogen reservoirs but also for engineered catalytic processes aimed at scalable, low-temperature hydrogen generation.