Dry reforming of methane (DRM) can convert greenhouse gases (CO2 and CH4) into value-added syngas (CO and H2), which is one of the promising approaches to achieve carbon neutrality. Designing coking resistant catalysts is still a challenge for an efficient DRM reaction. Here, we developed an efficient binary Mo–Ni catalyst through elucidating the promotional role of Mo in boosting the coking resistance of Ni-based catalysts during the DRM. Mo-modified ZSM-5 served as the “smart support”, which provided the dynamic variation between MoO x and MoO x C y , enabling efficient carbon removal during the DRM reaction. Furthermore, the introduction of Mo maintained more active Ni0 species and enhanced the activity. A more effective pathway via a formate intermediate driven by the Mo-modified Ni/ZSM-5 further suppressed coking during DRM. This work discovered that both activity and coking resistance of traditional Ni catalysts can be simultaneously improved due to the addition of Mo through restraining Ni oxidation and a unique MoO x ↔ MoC x O y redox cycle.
We report a highly efficient and stable electrode composed of a porous Fe-doped β-nickel hydroxide nanopyramid array supported on nickel foam (U–Fe-β-Ni(OH)2/NF) for overall water splitting. The unique structure is assembled via a self-templated strategy by utilizing the FeNi oxalate (FeNi–C2O4/NF) nanopyramid as the templates, followed by an anion-exchange reaction at room temperature. Due to the intrinsic activity of Fe-doped β-Ni(OH)2 along with unique porous array structures consisting of two-dimensional (2D) active materials on three-dimensional (3D) conductive substrates, the developed electrode exhibited outstanding electrocatalytic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline medium. The introduced amount of Fe plays a significant role in promoting OER and HER activity compared to the β-Ni(OH)2 electrode. The optimal electrode (U–Fe-β-Ni(OH)2/NF-2) generated a current density of 10 mA cm–2 at low overpotentials of 218 mV for the OER and 121 mV for the HER. The electrode also demonstrated considerably stable performance during the continuous water splitting process. Furthermore, we elucidated the promotion mechanisms of the active Fe-doped β-Ni(OH)2 compound for the OER and HER based on extensive characterization and electrochemical measurements. Hence, this work provides a facile approach to developing low-cost, efficient, and stable hydroxide-based electrodes for bifunctional OER and HER in water splitting.
Substantial improvements in cycle life, rate performance, accessible voltage, and reversible capacity are required to realize the promise of Li-ion batteries in full measure. Here, we have examined insertion electrodes of the same composition (V2O5) prepared according to the same electrode specifications and comprising particles with similar dimensions and geometries that differ only in terms of their atomic connectivity and crystal structure, specifically two-dimensional (2D) layered α-V2O5 that crystallizes in an orthorhombic space group and one-dimensional (1D) tunnel-structured ζ-V2O5 crystallized in a monoclinic space group. By using particles of similar dimensions, we have disentangled the role of specific structural motifs and atomistic diffusion pathways in affecting electrochemical performance by mapping the dynamical evolution of lithiation-induced structural modifications using ex situ scanning transmission X-ray microscopy, operando synchrotron X-ray diffraction measurements, and phase-field modeling. We find the operation of sharply divergent mechanisms to accommodate increasing concentrations of Li-ions: a series of distortive phase transformations that result in puckering and expansion of interlayer spacing in layered α-V2O5, as compared with cation reordering along interstitial sites in tunnel-structured ζ-V2O5. By alleviating distortive phase transformations, the ζ-V2O5 cathode shows reduced voltage hysteresis, increased Li-ion diffusivity, alleviation of stress gradients, and improved capacity retention. The findings demonstrate that alternative lithiation mechanisms can be accessed in metastable compounds by dint of their reconfigured atomic connectivity and can unlock substantially improved electrochemical performance not accessible in the thermodynamically stable phase.
Hydrogen is at the forefront of clean energy use and storage in the goal to drastically reduce anthropogenic carbon dioxide and combat global climate change. However, hydrogen production to-date is accomplished via steam methane reforming which, for every ton of hydrogen produced 5.5 tons of CO2 is liberated. One viable technical solution for production of clean hydrogen is water electrolysis. To this end DOE has implemented the Hydrogen Earthshot initiative to cleanly produce hydrogen at 2 $/kg by 2025 and 1 $/kg by 2030. Of the several commercial water electrolysis technologies available, proton exchange membrane water electrolysis (PEMWE) currently offers the most benefits including operations at low temperature, differential pressure, and high current density (≥3 A/cm2). Commercialization of PEMWE has advanced rapidly despite several significant disadvantages which include the necessity of scarce expensive platinum-group metal (PGM) catalysts, expensive perfluorinated membranes, and significant environmental impacts of perfluorinated alkyl substances (PFAS) used in membrane production. The solution to these challenges is the development of alkaline exchange membrane water electrolysis (AEMWE) which retains the advantageous characteristics of PEMWE without the need for PGM catalysts or perfluorinated membranes. Here in, we report on our current progress of AEMWEs, which covers PGM-free catalyst development, low-cost and durable AEM development and electrode design development. From a commercial point of view, given a high-performance durable membrane, manufacturing MEAs is a critical next step toward commercialization. Therefore, development of an AEM with accessible thermal transitions prior to the onset of quaternary ammonium degradation is key to enabling proven MEA fabrication techniques such as hot-pressing and decal transfer of electrodes. Through a novel synthetic approach, we will describe the preparation of functionalized copolymers and terpolymers containing latent cross-linking functionality. Ultimately, we will demonstrate the manufacturability of MEAs from our PGM-free catalysts and membrane materials employing hot-pressing and decal transfer of electrodes along with single cell evaluations. We will also discuss factors that affect the degradation of AEMWEs and solutions to address these challenges.
Hydrogen is a leading clean energy among the global initiatives to combat climate change. Currently, the primary source of hydrogen is produced from steam methane reforming (SMR), will produced 5.5 tons of carbon dioxide for every ton of hydrogen. Elimination of carbon dioxide in hydrogen production can be accomplished via water electrolysis.One commercially available water electrolysis system currently relies on proton exchange membrane (PEM) technology. Such electrolyzers require the use of expensive platinum group metal (PGM) catalysts and perfluorinated membranes. With respect to the PGM catalysts, iridium is used for the oxygen evolution reaction (OER) and only 7-8 tons of Ir is produced globally per year. Iridium’s scarcity and increased demand from PEM water electrolyzer (PEMWE) has led to its cost rising to > $6,400 per ounce. The reliance on PGM catalysts alone will significantly hinder the green hydrogen future. The solution to eliminating or dramatically reducing the need for PGM materials is alkaline exchange membrane water electrolysis.Alkaline exchange membrane electrolysis (AEMWE) is a burgeoning technology that combines a solid-state electrolyte (alkaline exchange membrane) with the ability to use PGM-free earth abundant catalyst materials. Currently AEMWE is in its adolescence. Many advancements have been made in membrane technology producing materials which are more chemically stable and operationally robust. Such advances have enabled demonstration of AEMWE without the use of supporting electrolyte thus further decreasing the technology’s cost witthout requiring corrosion resistant materials. Furthermore, advances in PGM-free catalysts, mainly NiFeM OER materials, have demonstrated comparable to improved performance with respect to iridium oxide. Therefore, the previous decade of research has indeed breathed increased interest and research effort into AEMWE.Here in, we report high performance and durability demonstrations of state of the art AEMWE technology. In this work, it is shown that the AEMWE with novel alkaline exchange membranes can operate for hundreds of hours on pure water only at 1000 mA/cm2. Such achievement is however not only limited to novel membrane development, but also due to membrane electrode assembly (MEA) design. The MEA fabrication is a critical step in determining performance and durability owing to the severely limited processing options in current alkaline exchange membrane technology. Furthermore, it is also demonstrated that in collaboration with the State University of New York Buffalo and University of Delaware, that NiFeM OER catalysts are indeed capable of replacing iridium oxide, achieving a similar potential of 1.8 V at 1000 mA/cm2.
An electrolyzer can utilize “off peak” electricity from solar or wind farms to produce hydrogen or other fuels. These chemicals can subsequently be operated in a fuel cell mode to generate electricity or used for other industrial applications. The power to green chemicals alone is poised to become a multi-billion-dollar market for on-site water electrolysis systems over the next decade. Some examples include green H2, NH3 or hydrocarbon fuels (e.g., methanol, ethanol, and ethylene) However, current green chemical production from electrolysis has not achieved viable commercialization due to expensive materials and low efficiency even if “free” electricity from renewable energy can be secured. Giner has been a world leader in researching, developing and manufacturing electrolyzers for green chemical synthesis. We have been committed to addressing the challenges of materials (catalyst, membrane, and bipolar plates) and processing conditions to improve electrolyzer efficiency, extend lifetime, and lower capital cost. These efforts include: 1) developing low-cost durable ion exchange membranes; 2) lowering platinum-group metal (PGM) catalyst loading; 2) discovering non-precious metal catalysts; 4) increasing corrosion resistance of separators and other hardware; 5) optimizing operating conditions. These efforts have therefore enhanced the conversion rate and process efficiency. For example, the electrochemical production of ammonia from nitrogen and water using rationally designed catalysts can lead to tremendous energy savings compared to conventional Haber-Bosch process. The electrochemical conversion of CO2 and water to ethylene can be significantly boosted by novel membrane design and optimizing optimal operating conditions. Due to high efficiency and lowered cost, the electrolysis technologies for green chemical production may become strongly competitive and complementary to conventional chemical manufactuaring industry.
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