Exploring metal oxides for the hydrogen evolution reaction (HER) in the field of nanotechnology

Harnessing bimetallic spinel cobaltite with hematite for electrocatalytic overall water splitting: A comprehensive experimental & theoretical study

Electrocatalytic water splitting presents a potential avenue for hydrogen production, paving the path towards a green and sustainable economy. This study focuses on the fabrication of hematite and transition-metal cobaltite (NiCo2O4@Fe2O3) based bifunctional catalyst for overall water splitting. The carefully engineered NiCo2O4 nanospheres and α-Fe2O3 nanoneedles exhibit enhanced performance, highlighting the critical role of morphology in determining the availability of active sites and surface area, which in turn leads to improved catalytic activity. In this study, the optimized NiCo2O4@Fe2O3 nanocomposite showing the current density of 50 mA/cm2 at 264 mV overpotential with a Tafel slope of 67 mV/dec and 21.9 mF/cm2 of Cdl value with corresponding electrochemical active surface area (ECSA) of 438 cm2 for oxygen evolution reaction (OER). Similarly, in hydrogen evolution reaction (HER), 201 mV of overpotential is required to attain 50 mA/cm2 current density. The observed Tafel, Cdl and ECSA were 43 mV/dec, 21.1 mF/cm2, and 422 cm2, respectively. In the light of its excellent bifunctional activity full-cell studies were carried out to ensure the efficiency and robustness in overall water splitting, which exhibits the cell potential of 1.73 V to attain 50 mA/cm2 current density. Theoretical investigations supported these findings by revealing potential electron transfer mechanisms and structural stability.

Multifunctional iron-cobalt heterostructure (FeCoHS) electrocatalysts: accelerating sustainable hydrogen generation through efficient water electrolysis and urea oxidation

The urgent need to address escalating environmental pollution and energy management challenges has underscored the importance of developing efficient, cost-effective, and multifunctional electrocatalysts. To address these issues, we developed an eco-friendly, cost-effective, and multifunctional electrocatalyst via a solvothermal synthesis approach. Due to the merits of the ideal synthesis procedure, the FeCoHS@NF electrocatalyst exhibited multifunctional activities, like OER, HER, OWS, UOR, OUS, and overall alkaline seawater splitting, with required potentials of 1.48, 0.130, 1.59, 1.23, 1.40, and 1.54 V @ 10 mA cm-2, respectively. Moreover, electrolysers required only 1.40 V at 10 mA cm-2 for energy-saving urea-assisted hydrogen production, which was 190 mV lower than that of the alkaline water electrolyser. The alkaline sewage and seawater purification setup combined with the FeCoHS@NF electrolyzer led to a novel approach of producing pure green hydrogen and water. The ultrastability of the FeCoHS@NF electrocatalyst for industrial applications was confirmed using chronopotentiometry at 10 and 100 mA cm-2 over 110 h for OER, HER, UOR, and overall water splitting. The production of hydrogen using the FeCoHS@NF electrocatalyst in alkaline sewage water and seawater offers multiple benefits, including generation of renewable hydrogen energy, purification of wastewater, reduction of environmental pollutants, and low cost and low electricity consumption of the electrolyser system.

Abu-Dief A, El-Dabea T. Functionalization of Nanomaterials for Energy Storage and Hydrogen Production Applications

This review article provides a comprehensive overview of the pivotal role that nanomaterials, particularly graphene and its derivatives, play in advancing hydrogen energy technologies, with a focus on storage, production, and transport. As the quest for sustainable energy solutions intensifies, the use of nanoscale materials to store hydrogen in solid form emerges as a promising strategy toward mitigate challenges related to traditional storage methods. We begin by summarizing standard methods for producing modified graphene derivatives at the nanoscale and their impact on structural characteristics and properties. The article highlights recent advancements in hydrogen storage capacities achieved through innovative nanocomposite architectures, for example, multi-level porous graphene structures containing embedded nickel particles at nanoscale dimensions. The discussion covers the distinctive characteristics of these nanomaterials, particularly their expansive surface area and the hydrogen spillover effect, which enhance their effectiveness in energy storage applications, including supercapacitors and batteries. In addition to storage capabilities, this review explores the role of nanomaterials as efficient catalysts in the hydrogen evolution reaction (HER), emphasizing the potential of metal oxides and other composites to boost hydrogen production. The integration of nanomaterials in hydrogen transport systems is also examined, showcasing innovations that enhance safety and efficiency. As we move toward a hydrogen economy, the review underscores the urgent need for continued research aimed at optimizing existing materials and developing novel nanostructured systems. Addressing the primary challenges and potential future directions, this article aims to serve as a roadmap to enable scientists and industry experts to maximize the capabilities of nanomaterials for transforming hydrogen-based energy systems, thus contributing significantly to global sustainability efforts.

Advances in Catalysts for Hydrogen Production: A Comprehensive Review of Materials and Mechanisms

This review explores the recent advancements in catalyst technology for hydrogen production, emphasizing the role of catalysts in efficient and sustainable hydrogen generation. This involves a comprehensive analysis of various catalyst materials, including noble metals, transition metals, carbon-based nanomaterials, and metal-organic frameworks, along with their mechanisms and performance outcomes. Major findings reveal that while noble metal catalysts, such as platinum and iridium, exhibit exceptional activity, their high cost and scarcity necessitate the exploration of alternative materials. Transition metal catalysts and single-atom catalysts have emerged as promising substitutes, demonstrating their potential for enhancing catalytic efficiency and stability. These findings underscore the importance of interdisciplinary approaches to catalyst design, which can lead to scalable and economically viable hydrogen production systems. The review concludes that ongoing research should focus on addressing challenges related to catalyst stability, scalability, and the integration of renewable energy sources, paving the way for a sustainable hydrogen economy. By fostering innovation in catalyst development, this work aims to contribute to the transition towards cleaner energy solutions and a more resilient energy future.

Recent Progress and Perspectives on Functional Materials and Technologies for Renewable Hydrogen Production

Scientists worldwide have been inspecting hydrogen production routes and showing the importance of developing new functional materials in this domain. Numerous research articles have been published in the past few years, which require records and analysis for a comprehensive bibliometric and bibliographic review of low-carbon hydrogen production. Hence, a data set of 297 publications was selected after filtering journal papers published since 2010. The search keywords in the Scopus Database were "green hydrogen" and "low carbon hydrogen production and materials". The data were analyzed using the R Bibliometrix package. This analysis made it possible to determine the total annual publication rate and to segregate it by country, author, journal, and research institution. With a general upward trend in the total number of publications, China was identified as the leading country in research on the subject, followed by Germany and Korea. Keyword analysis and the chronological evolution of several important publications related to the topic showed the focus was on water splitting for low-carbon H2 production. Finally, this review provides future directions for technologies and functional materials for low-carbon hydrogen production.

Enhanced Hydrogen Evolution Reaction Using Biomass-Activated Carbon Nanosheets Derived from Eucalyptus Leaves

Carbonaceous-based metal-free catalysts are promising aspirants for effective electrocatalytic hydrogen generation. Herein, we synthesized mesoporous-activated carbon nanosheets (ELC) from biomass eucalyptus leaves through KOH activation. The microstructure, structural, and textural characteristics of the prepared materials were characterized by FE-SEM, Raman, XRD, and BET measurements. The high temperature (700 °C) KOH-activated ELC nanosheets exhibited an interconnected nanosheet morphology with a large specific surface area (1436 m2/g) and high mesoporosity. The ELC-700 catalyst exhibited an excellent electrocatalytic HER performance with a low overpotential (39 mV at 10 mA/cm2), excellent durability, and a Trivial Tafel slope (36 mV/dec) in 0.5 M H2SO4 electrolyte. These findings indicate a new approach for developing excellent biomass-derived electrocatalysts for substantially efficient green hydrogen production.

Biology-Based Synthesis of Nickel Single Atoms on the Surface of Geobacter sulfurreducens as an Efficient Electrocatalyst for Alkaline Water Electrolysis

Single-atom metal catalysts are promising electrocatalysts for water electrolysis. Nickel-based electrocatalysts have shown attractive application prospects for water electrolysis. However, synthesizing stable Ni single atoms using chemical and physical approaches remains a practical challenge. Here, a facile and precise method for synthesizing stable nickel single atoms on the surface of Geobacter sulfurreducens using a microbial-mediated extracellular electron transfer (EET) process is demonstrated. It is shown that G. sulfurreducens can effectively anchor nickel single atoms on their surface. X-ray absorption near-edge structure and Fourier-transformed extended X-ray absorption fine structure spectroscopy confirm that the nickel single atom is coordinated to nitrogen in the cytochromes. The as-synthesized nickel single atoms on G. sulfurreducens exhibit excellent bifunctional catalytic properties for alkaline water electrolysis with low overpotential (η) to achieve current density (10 mA cm-2) for both hydrogen evolution reactions (η = 80 mV) and oxygen evolution reaction (η = 330 mV) with minimal catalyst loading of 0.0015 mg Ni cm-2. The nickel single-atom catalyst shows long-term stability at a constant electrode potential. This synthesis method based on the EET capability of electroactive bacteria provides a simple and scalable approach for producing low-cost and highly efficient nonnoble transition metal single-atom catalysts for practical applications.