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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Co 2 P-Pt Heterostructure Interfaces for Electrocatalytic Hydrogen Evolution

Pt-based electrocatalysts are effective for the hydrogen evolution reaction (HER); however, their limited ability to facilitate water dissociation and suboptimal hydrogen binding energy (H BE ) in alkaline electrolytes result in slow reaction kinetics, which hinders their cost-efficiency and practical applications. This study reports the synthesis of Co 2 P-Pt heterostructure nanorods using a seed-mediated growth method, producing a high density of Co 2 P-Pt interfacial sites. Density functional theory (DFT) calculations indicate that electronic interactions at these interfaces optimize H BE on Pt, while the interfacial sites promote water dissociation. The Co 2 P-Pt nanorods demonstrate an overpotential of 14 mV at 10 mA cm −2 for the HER, highlighting the potential of precisely engineered metal-metal phosphide interfaces for enhancing electrocatalytic efficiency.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electrodeposition of Fe–Ni alloy on Au(111) substrate: Metastable BCC growth via hydrogen evolution and interactions

The electrodeposition of Fe–Ni alloy is usually complicated by the effects of anomalous codeposition and hydrogen evolution. Although the influence of the deposition conditions on the alloy composition has been studied extensively, very few works considered the influence of growth conditions on the phase constitution. In this work, various electrodeposition conditions were investigated to grow Fe–Ni alloy films (<30 nm) with similar compositions in the Invar-to-equiatomic range on Au (111) substrate. Highly (110) oriented BCC phase Fe–Ni with a Ni fraction (ca. 40 at.% Ni) well beyond the equilibrium solubility limit (5 at.% Ni) was obtained with a significant alloy deposition partial current. An increase in the fraction of the BCC phase was found to be associated with a higher alloy deposition partial current, but not necessarily with an increase in the hydrogen evolution partial current. Motivated by the findings from this work, the formation of the metastable BCC phase is speculated to depend on the competing kinetics between the inclusion and desorption of hydrogen adatoms at the electrodeposited growth front.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Revisiting trends in the exchange current for hydrogen evolution

Nørskov and collaborators proposed a simple kinetic model to explain the volcano relation for the hydrogen evolution reaction on transition metal surfaces such that j 0 = k 0 f(ΔG H ) where j 0 is the exchange current density, f(ΔG H ) is a function of the hydrogen adsorption free energy ΔG H as computed from density functional theory, and k 0 is a universal rate constant. Herein, focusing on the hydrogen evolution reaction in acidic medium, we revisit the original experimental data and find that the fidelity of this kinetic model can be significantly improved by invoking metal-dependence on k 0 such that the logarithm of k 0 linearly depends on the absolute value of ΔG H . Here, we further confirm this relationship using additional experimental data points obtained from a critical review of the available literature. Our analyses show that the new model decreases the discrepancy between calculated and experimental exchange current density values by up to four orders of magnitude. Furthermore, we show the model can be further improved using machine learning and statistical inference methods that integrate additional material properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Modulating Iron Crystals with Lattice Chalcophile‐Siderophile Elements for Selective Dechlorinations Over Hydrogen Evolution

Selective dechlorination of organic chlorides over hydrogen evolution reaction (HER) remains a challenge because of their coincidence. Nanoscale zerovalent iron (nFe 0 ) draws a promising picture of in situ groundwater dechlorination, but its indiscriminate reactivity limits the application. Here, nFe 0 crystals are designed with electron shuttles and improved hydrophobic nature based on elemental chalcophile-siderophile characteristics, where chalcophile-siderophile S served as a bridge to allow impregnating nFe 0 crystals with weakly siderophile and strongly chalcophile Cu. Even impregnations of lattice chalcophile-siderophile elements into the nFe 0 crystals are evidenced at both intraparticle and individual-particle levels. The modulated Fe microenvironment and physicochemical properties broke the reactivity-selectivity-longevity-stability trade-off. Compared to nFe 0 , superhydrophobic Cu─S─nFe 0 with lattice expansion promoted dechlorination by 20-fold but inhibited HER by 150-fold, utilizing ≈80–100% electrons from the Fe 0 reservoir. This work demonstrates the concept of engineering nFe 0 lattice with tunable structure-property relationships, mimicking reductive dehalogenases by selectively interacting with halocarbon functional groups for efficient dehalogenation and sustainable groundwater remediation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Two-Dimensional Polycyclic Photovoltaic Molecule with Low Trap Density for High-Performance Photocatalytic Hydrogen Evolution

Typical organic semiconductors show a high trap density of states (10 16 –10 18 cm -3 ), providing a large number of centers for charge-carrier recombination, thus hindering the development of photocatalytic hydrogen evolution. In this report we design and synthesize a two-dimensional polycyclic photovoltaic material, named as TPP, to reduce the trap density to as low as 2.3×10 15 cm -3 , which is 1–3 orders of magnitude lower than those of typical organic semiconductors. Moreover, TPP exhibits a broad and strong absorption, ordered molecular packing with a large crystalline coherence length and enhanced electron mobility. Then, the bulk heterojunction nanoparticles (BHJ-NPs) based on a blend of polymer donor (PM6) and TPP exhibit an average hydrogen evolution rate (HER) of 64.31 mmol h -1 g -1 under AM1.5G sunlight (100,mW cm -2 ), and 72.75 mmol h -1 g -1 under 330–1100 nm illumination (198 mW cm -2 ) higher than that of the control NPs based on typical PM6 : Y6 (62.67 mmol h -1 g -1 ).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

How the Arrangement of Platinum Atoms on Ruthenium Nanoparticles Improves Hydrogen Evolution Activity

The platinum‐ruthenium (PtRu) system is highly active for hydrogen evolution reaction (HER) in alkaline media with both Pt and Ru playing active roles in the water dissociation step that generates adsorbed hydrogen atoms. Precise control of the arrangement of Pt atoms on Ru nanoparticles can maximize the Pt‐Ru sites for water dissociation and Pt‐Pt sites for hydrogen production and can considerably improve HER catalytic performance. By directing the growth and distribution of Pt on Ru hourglass nanoparticles, the arrangement of Pt on Ru is controlled into forming Pt islands, small Pt clusters, and strings of a few Pt atoms. Calculations show that the unique atomic string arrangements of Pt on Ru is the thermodynamically favorable configuration. Additionally, these strings have a favorable combination of Pt‐Ru and Pt‐Pt sites, making the Pt‐string on Ru the most active catalyst with a more than fivefold increase in turnover frequency for alkaline HER compared to the Pt‐island on Ru catalyst. The results show how controlling the Pt atomic arrangement on Ru nanoparticle surfaces for the tuning of Pt‐Pt and Pt‐Ru neighboring sites can direct toward a more efficient HER mechanism and thereby significantly enhancing HER performance.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Nb 2 O 5 Protection Layers for Hydrogen Evolution by p-InP Photocathodes in Acidic Electrolytes

Coatings of HfO 2 , Ta 2 O 5 , TiO 2 , and Nb 2 O 5 were evaluated as protection layers for p-InP photocathodes in aqueous acidic electrolytes. Each candidate protection layer was characterized based on interfacial conduction of photogenerated electrons, the thermodynamic and kinetic stability of the overlayer over the relevant potential and pH range for cathodic fuel-forming half-reactions, and inhibition of the primary anodic and/or chemical dissolution processes that limit electrode stability. The conduction of photogenerated electrons and inhibition of anodic oxidation was evaluated using V 3+ / 2+ in 5.0 M HCl(aq) as a one-electron redox couple with a potential close to that of hydrogen evolution in acidic media. Failure modes due to cathodic plating of metal, as well as anodic dissolution and chemical dissolution processes, were evaluated for photocathodes made from etched p-InP, platinized p-InP, and p-InP photoelectrodes that had been coated with the various oxide films and then platinized for use in photoelectrochemical hydrogen evolution in acidic aqueous electrolytes. Nb 2 O 5 best met all of the criteria, contrasting with TiO 2 , which is thermodynamically and kinetically unstable in acid over the potential range relevant for the hydrogen evolution and/or CO 2 reduction electrochemical half-reactions. Furthermore, these protocols should be useful for other materials and semiconductors to determine the effectiveness of protection layers for photocathodes.

Electrodes↗
DOE OSTI2022

Insights into the Hydrogen Evolution Reaction on 2D Transition-Metal Dichalcogenides

Understanding hydrogen evolution reaction (HER) behaviors over two-dimensional transition-metal dichalcogenides (2D-TMDs) is critical for the development of nonprecious HER electrocatalysts with better activity. Here, in this work, by combining density functional theory calculations with microkinetic modeling, we thoroughly investigated the HER mechanism on 2D-TMDs. We find an important dependence of simulated cell size on the calculated hydrogen adsorption energy and the activation barrier for MoS 2 . Distinct from previous “H migration” mechanisms proposed for the Heyrovsky reaction, the rate-determining step for MoS 2 , we propose that the Mo site only serves as the stabilized transition state rather than H adsorption. In comparison to transition-metal electrocatalysts, we find that the activation barrier of the Heyrovsky reaction on 2D-TMDs scales with the hydrogen adsorption energy exactly as for transition metals except that all activation energies are displaced upward by ca. 0.4 eV. This higher Heyrovsky activation barrier is responsible for the substantially lower activity of 2D-TMDs. We further show that this higher activation barrier stems from the more positively charged adsorbed hydrogen on the chalcogenides interacting repulsively with the incoming proton. Based on these insights, we discuss potential strategies for the design of nonprecious HER catalysts with activity comparable to Pt.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Metal-free photocatalysts for hydrogen evolution

This review focuses on the discussion of the latest progress and remaining challenges in selected metal-free photocatalysts for hydrogen production. The scope of this review is limited to the metal-free elemental photocatalysts (i.e. B, C, P, S, Si, Se etc.), binary photocatalysts (i.e. BC 3 , B 4 C, C x N y , h-BN etc.) and their heterojunction, ternary photocatalysts (i.e. BCN) and their heterojunction, and different types of organic photocatalysts (i.e. linear, covalent organic frameworks, microporous polymer, covalent triazine frameworks etc.) and their heterostructures. Following a succinct depiction of the latest progress in hydrogen evolution on these photocatalysts, discussion has been extended to the potential strategies that are deemed necessary to attain high quantum efficiency and high solar-to-hydrogen (STH) conversion efficiency. Issues with reproducibility and the disputes in reporting the hydrogen evolution rate have been also discussed with recommendations to overcome them. A few key factors are highlighted that may facilitate the scalability of the photocatalyst from microscale to macroscale production in meeting the targeted 10% STH. This review is concluded with additional perspectives regarding future research in fundamental materials aspects of high efficiency photocatalysts followed by six open questions that may need to be resolved by forming a global hydrogen taskforce in order to translate bench-top research into large-scale production of hydrogen.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Graphene-transition metal catalyst for hydrogen evolution reaction

Functionalized catalysts for use in a hydrogen evolution reaction (HER) contain nanoparticles containing a transition metal enveloped in layers of graphene, which renders the nanoparticles resistant to passivation while maintaining an optimal ratio of transition metal and transition metal oxide in the nanoparticles. The catalysts can be utilized with anionic exchange polymer membranes for hydrogen production by alkaline water electrolysis.

Mukerjee, Sanjeev↗
DOE OSTI2020

Effects of Surface Terminations of 2D Bi 2 WO 6 on Photocatalytic Hydrogen Evolution from Water Splitting

Two-dimensional (2D)-structured photocatalysts with atomically thin layers not only have the potential to enhance hydrogen generation efficiency but also allow more direct investigations of the effects of surface terminations on photocatalytic activity. In this work, taking 2D Bi 2 WO 6 as a model, we found that the configuration of bilayer Bi 2 O 2 sandwiched by alternating WO 4 layers enabled the thermodynamic driving potential for photocatalytic hydrogen evolution. Without Pt deposition, the H 2 generation efficiency can reach to 56.9 μmol/g/h by 2D Bi 2 WO 6 as compared with no activity of Bi 2 WO 6 nanocrystals under simulated solar light. This configuration is easily functionalized by adsorption of Cl – /Br – to form Bi–Cl/Bi–Br bonds, which leads to the decrease of recombination in photogenerated charge carriers and narrower band gaps. This work highlights an effective way to design photocatalysts with efficient hydrogen evolution by tuning the surface terminations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Through the interface: New insights of the hydrogen evolution and oxidation reactions in aqueous solutions

Abstract Hydrogen evolution and oxidation reactions (HER/HOR) are the most fundamental reactions in electrocatalysis. Despite the practical significance, the mechanisms of HER/HOR in aqueous solutions are still elusive. Various theories have been proposed to rationalize the pH effect, cation effect, and structure effect of HER/HOR but none of them can explain all observations. In this review, we discuss four schools of thought for the HER/HOR, focusing on the strengths and shortcomings of each hypothesis and highlighting the magnitude of electrochemical interface structure in hydrogen electrocatalysis.

Liu, Ershuai↗
DOE OSTI2023

Characterization of paramagnetic states in an organometallic nickel hydrogen evolution electrocatalyst

Abstract Significant progress has been made in the bioinorganic modeling of the paramagnetic states believed to be involved in the hydrogen redox chemistry catalyzed by [NiFe] hydrogenase. However, the characterization and isolation of intermediates involved in mononuclear Ni electrocatalysts which are reported to operate through a Ni I/III cycle have largely remained elusive. Herein, we report a Ni II complex (NCHS2)Ni(OTf)2, where NCHS2 is 3,7-dithia-1(2,6)-pyridina-5(1,3)-benzenacyclooctaphane, that is an efficient electrocatalyst for the hydrogen evolution reaction (HER) with turnover frequencies of ~3,000 s −1 and a overpotential of 670 mV in the presence of trifluoroacetic acid. This electrocatalyst follows a hitherto unobserved HER mechanism involving C-H activation, which manifests as an inverse kinetic isotope effect for the overall hydrogen evolution reaction, and Ni I /Ni III intermediates, which have been characterized by EPR spectroscopy. We further validate the possibility of the involvement of Ni III intermediates by the independent synthesis and characterization of organometallic Ni III complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Orbital engineering of C 3 N monolayer to design efficient synergistic sites electrocatalyst for boosting alkaline hydrogen evolution

Alkaline water electrolyzer (AWE) is one of the promising technologies for hydrogen production at the industrial level. However, energetic inefficiency and low current density impede the development of AWE. Compared with acidic conditions, the Volmer step in alkaline hydrogen evolution reaction (HER) involves extra water dissociation, whose barrier is one of the most vital reasons for the sluggish kinetics of alkaline HER. Herein, choosing C 3 N monolayer as an ideal theoretical model, we design several empty orbitals through intentional metal doping, and further construct synergistic sites on the C 3 N monolayer to accelerate both water dissociation and hydrogen adsorption for alkaline HER. Furthermore, the as-designed Be-doped and Cr-doped C 3 N monolayers exhibit rather low theoretical overpotential of 0.476 eV and 0.216 eV for alkaline HER, respectively, which are even lower than Pt (1 1 1) surface. Moreover, by comparing the water dissociation behaviors on metal-doped C3N monolayer, we find that the empty orbitals with suitable orientation and energy level are useful for promoting the water dissociation process, indicating that we can use orbital engineering strategy to regulate the adsorption strength between adsorbate and surface site. Consequently, it is reasonable to suggest that our orbital engineering strategy would significantly benefit the design of highly efficient alkaline HER electrocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Trace levels of PtRu on NiMo foam electrodes towards hydrogen evolution reaction

Electrochemical water splitting plays a critical role in high purity hydrogen production. To lower capital cost and energy consumption, efficient catalysts are required to boost the hydrogen evolution reaction (HER), especially in alkaline media. Although PtRu alloy materials are still considered the state-of-the-art catalyst for the HER under alkaline media, large-scale application is hindered by its scarcity and high cost. NiMo alloy catalysts can be potential Pt-free alternatives to drive the sluggish kinetics of the HER under alkaline media, but their HER activity is still not ideal due to the limitation of Volmer step. Herein, we investigated the impact of trace levels of PtRu catalysts on NiMo electrodes towards the HER by incorporating advantages of both PtRu and NiMo catalysts to minimize cost and maintain a promising HER activity. Trace levels of PtRu catalysts from 0.0173 to 0.2648 mg cm −2 were loaded on commercial NiMo foam electrodes by a facile electrodeposition technique utilizing ppm concentration levels of PtRu in electrolyte. The results show that 0.0173 mg cm −2 PtRu loading on NiMo electrode can significantly enhance HER activity compared to the pristine NiMo foam electrode (Tafel slopes drop from ∼170 to ∼60 mV dec −1 ) due to the remarkable decline of energy barriers towards water dissociation and hydrogen adsorption. Meanwhile, the rate determining step (RDS) switches from the Volmer step to the Heyrovsky step when the PtRu loading increases to 0.0675 mg cm −2 . Promising catalytic stability is observed at 100 mA cm −2 over the course of 50 h with a PtRu loading of 0.1198 mg cm −2 . In conclusion, this work demonstrates a potential strategy to decrease the cost and simultaneously maintain superior HER performance by integrating trace levels of PtRu catalyst with NiMo foam electrodes.

Electrochemical water splitting↗
DOE OSTI2020

Enhanced Electrocatalytic Hydrogen Evolution Activity in Single-Atom Pt-Decorated VS 2 Nanosheets

Enhancing catalytic activity by decorating noble metals in catalysts provides an opportunity for promoting the electrocatalytic hydrogen evolution reaction (HER) application. However, there are few systematic studies on regulating the structures of noble metals in catalytic materials and investigating their influence on HER. Herein, Pt catalysts with different structures including single atoms (SAs), clusters, and nanoparticles well-controllably anchored on VS 2 nanosheets through a cost-effective optothermal method are reported, and their HER performance is studied. The most efficient Pt-decorated VS 2 catalyst (with both Pt SAs and clusters) delivers an overpotential of 77 mV at 10 mA cm –2 , close to that of Pt/C (48 mV). However, the optimal mass activity of Pt (normalizing to Pt content) is obtained from only SA Pt-decorated VS 2 (i.e., 22.88 A mg Pt –1 at 200 mV) and is 12 times greater than that of the Pt/C (1.87 A mg Pt –1 ), attributed to the greatly enhanced Pt utilization. Additionally, the theoretical simulations reveal that Pt SA decoration makes the adsorption free energy of H* closer to the thermoneutral value and improves the charge-transfer kinetics, significantly enhancing HER activity. Furthermore, this work offers a pathway to prepare the desired catalyst based on synergy of Pt structures and VS 2 and reveals the intrinsic mechanism for enhancing catalytic activity, which is important for HER applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effects of Peptide-Functionalized Surfaces on the Electrochemical Hydrogen Evolution Reaction

Abstract This review outlines the approaches and mechanisms through which peptides and amino acids functionalize electrocatalytically active surfaces to promote or inhibit the electrochemical hydrogen evolution reaction (HER). HER is important in many electrochemical systems. For example, HER is highly desired in water electrolysis, which if driven by renewable energy could serve as a green alternative to the fossil-fuel-driven steam methane-reforming process. However, HER is often an undesired side reaction and thus limits the selectivity of promising electrochemical technologies such as electrochemical nitrogen reduction or carbon dioxide reduction. In pursuing higher product selectivity and yield in emerging and existing electrochemical systems, amino acids and short-chain peptides are promising molecules for the modification of electrochemically active surfaces. Peptides are attractive because they are highly tunable, which allows for versatility in their applications. This short review article summarizes literature that illustrates the mechanisms through which electrode-bound peptides can affect HER including via modulating surface binding and adsorbate coverage, altering the surface composition, and controlling proton transfer rates. Our goal is to motivate additional studies utilizing electrode-bound peptides to modulate electrochemical hydrogen evolution reactions.

Electrochemistry↗
DOE OSTI2023

Correlating Experimentally Determined Hydrogen Binding Energy with Hydrogen Evolution Activity over Metal Monolayers on Molybdenum Nitride

It is well established that hydrogen binding energy (HBE) is a key descriptor for hydrogen evolution reaction (HER) activity, and such a relationship is a useful tool for searching efficient and cost-effective HER catalysts. However, in almost all cases, the HBE values are obtained from density functional theory (DFT) calculations. Here in this study, temperature programmed desorption (TPD) was used to experimentally determine the HBE values of metal monolayers supported on molybdenum nitride (Mo 2 N), and electrochemical measurements were performed on the same surfaces. Combined DFT and kinetic Monte Carlo (kMC) simulations were used to validate the trend observed with TPD and the electrochemical HER activity. Depositing one monolayer of Pt on Mo 2 N led to similar HBE values seen for bulk Pt, and electrochemical measurements showed that monolayer Pt on Mo 2 N had similar HER activity to that of bulk Pt. Similar studies were also performed for monolayer Pd on Mo 2 N to confirm the correlation. This work also demonstrates that Mo 2 N is a promising support to reduce precious metal loading in HER catalysts.

08 HYDROGEN↗