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Abstract:

External magnetic fields emerge as a promising method for enhancing the electrocatalytic oxygen evolution reaction (OER), yet the underlying magneto‐electric (ME) mechanisms are not well understood. The slow kinetics of OER make it a key challenge in electrocatalytic water‐splitting, a promising technique for sustainable H2 fuel production. Herein, a systematic approach is presented to analyzing the ME mechanisms governing OER, using metallic‐plate (Ni foam, Ni sheet, and Pt sheet) and powder‐based (Co3O4/BaFe12O19 on carbon paper) electrodes. Through controlled experiments using varying magnetic field strengths and orientations, Lorentz force and spin‐polarization mechanisms are separated. For metallic electrodes, the effects are orientation‐dependent, indicating domination by Lorentz force. Magnetic flux density about the electrode surface is shown to govern the Lorentz force behavior. Interestingly, a “pseudo” effect is discovered which results from the relative position of the reference electrode, highlighting the importance of experimental design. The Co3O4 systems display minimal orientation dependence, indicating spin‐polarization domination. Introducing BaFe12O19 as a magnetic co‐catalyst further amplifies the ME effect, marking the first demonstration of magnetic co‐catalyst enhancement in magneto‐electrocatalysis. This work provides key insights into ME mechanisms, linking electrode composition, magnetism, and geometry to performance, offering new pathways for optimizing future magneto‐electrocatalytic systems.

Abstract:

Green ammonia evolution by photocatalytic means has gained significant attention over recent decades, however, the energy conversion efficiency remains unsatisfactory, and deep mechanistic insights are absent. Here in this work, this challenge is addressed by developing a photothermal system that synthesizes ammonia from nitrogen and natural seawater under simulated solar irradiation, employing ruthenium‐doped barium tantalum oxynitride semiconductors. This method significantly enhances solar‐to‐ammonia conversion efficiency, providing a viable alternative to the energy‐intensive Haber–Bosch process. Optimized at 240 °C, the system achieves an ammonia evolution rate of 5869 µmol g−1 h−1 in natural seawater. Moreover, detailed characterizations have shown that the use of seawater not only leverages an abundant natural resource but also improves the reaction kinetics and overall system stability. The catalysts maintain their activity and structural integrity over multiple cycles, demonstrating both the feasibility and the durability of this innovative system. Achieving a solar‐to‐ammonia efficiency of 13% and an overall energy conversion efficiency of 6.3%, this breakthrough highlights the potential to decentralize ammonia production, enhancing accessibility and sustainability. This approach combines the benefits of thermal and photocatalytic processes, marking a significant advancement in ammonia synthesis technology.

Abstract:

The integration of an external magnetic field into electrocatalysis, termed magneto‐electrocatalysis, can target efficiency challenges in the oxygen evolution reaction (OER). Reaction rates can be enhanced through improved mass transport of reactants and products, manipulation of spin states, and lowered resistance. The OER is a kinetic bottleneck in electrocatalytic water splitting for sustainable hydrogen fuel. Previous studies lack comprehensive analyses and consistent reporting of magnetic field effects, resulting in varied interpretations. To establish optimized and reliable systems at larger scales, significant research advancements are required. This perspective explores the complex impact of magnetic fields on OER, emphasizing the interplay between various mechanisms such as spin‐polarization of oxygen intermediates, Lorentz force‐induced magnetohydrodynamics, and magnetoresistance. Here, how experimental design – such as electrode magnetism, shape, positioning, and reactor setup – can significantly influence these mechanisms is highlighted. Through a comprehensive review of current studies, major knowledge gaps and propose methodologies are identified to improve experimental reproducibility and comparability. This article aims to guide researchers toward the development of more efficient, scalable systems that leverage magnetic fields to enhance water splitting to push forward commercial green hydrogen production.

Abstract:

Since its advent in 2011, black titanium oxide (B-TiOx) has garnered significant attention due to its exceptional optical characteristics, notably its enhanced absorption spectrum ranging from 200 to 2000 nm, in stark contrast to its unmodified counterpart. The escalating urgency to address global climate change has spurred intensified research into this material for sustainable hydrogen production through thermal, photocatalytic, electrocatalytic, or hybrid water-splitting techniques. The rapid advancements in this dynamic field necessitate a comprehensive update. In this review, we endeavor to provide a detailed examination and forward-looking insights into the captivating attributes, synthesis methods, modifications, and characterizations of B-TiOx, as well as a nuanced understanding of its physicochemical properties. We place particular emphasis on the potential integration of B-TiOx into solar and electrochemical energy systems, highlighting its applications in green hydrogen generation, CO2 reduction, and supercapacitor technology, among others. Recent breakthroughs in the structure–property relationship of B-TiOx and its applications, grounded in both theoretical and empirical studies, are underscored. Additionally, we will address the challenges of scaling up B-TiOx production, its long-term stability, and economic viability to align with ambitious future objectives.

Abstract:

The development of new recyclable and inexpensive electrochemically active species for water oxidation catalysis is the most crucial step for future utilization of renewables. Particularly, transition metal complexes containing internal multiple, cooperative metal centers to couple with redox catalysts in the inorganic Keggin-type polyoxometalate (POM) framework at high potential or under extreme pH conditions would be promising candidates. However, most reported Ni-containing POMs have been highly unstable towards hydrolytic decomposition, which precludes them from application as water oxidation catalysts (WOCs). Here, we have prepared new tri-Ni-containing POMs with variable oxidation states by charge tailored synthetic strategies for the first time and developed them as recyclable POMs for water oxidation catalysts. In addition, by implanting corresponding POM anions into the positively charged MIL-101(Cr) metal–organic framework (MOF), the entrapped Ni2+/Ni3+ species can show complete recyclability for water oxidation catalysis without encountering uncontrolled hydrolysis of the POM framework. As a result, a low onset potential of approximately 1.46 V vs. NHE for water oxidation with stable WOC performance is recorded. Based on this study, rational design and stabilization of other POM-electrocatalysts containing different multiple transition metal centres could be made possible.