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Results for “electrocatalytic hydrogenation”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Synthesis of Synergistic Nitrogen-Doped NiMoO 4 /Ni 3 N Heterostructure for Implementation of an Efficient Alkaline Electrocatalytic Hydrogen Evolution Reaction

Electrochemical water splitting is considered as an effective and promising method to produce the ideal hydrogen energy to solve the energy crisis and environmental pollution problems. In this paper, we successfully synthesized the N-doped NiMoO 4 /Ni 3 N heterostructure, which exhibited an efficient HER performance with a lower overpotential of 51 mV at 10 mA cm -2 and a lower Tafel slope value of 45.47 mV dec -1 compared with those of NiMoO 4 , N-doped NiMoO 4 , or Ni 3 N owing to the synergistic effect of N doping and construction of the superior heterostructure. When the N-doped NiMoO 4 /Ni 3 N heterostructure is used as a cathode and the well-recognized excellent OER material (NiFe-LDH) is used as an anode to construct the two-electrode electrolyzer, the system requires only 1.506 and 1.559 V to achieve the current densities of 10 and 20 mA cm -2 , respectively, which are lower than those of the commercial Pt/C//RuO 2 system (1.573 and 1.634 V, respectively) or many other reported systems. At the same time, this two-electrode system demonstrates excellent durability in electrocatalytic water splitting. This design method paved the way for the development of another electrocatalytic system.

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

Cu[Ni(2,3-pyrazinedithiolate) 2 ] Metal–Organic Framework for Electrocatalytic Hydrogen Evolution

The application of metal–organic frameworks (MOFs) as electrocatalysts for small molecule activation has been an emerging topic of research. Previous studies have suggested that two-dimensional (2D) dithiolene-based MOFs are among the most active for the hydrogen evolution reaction (HER). Here, a three-dimensional (3D) dithiolene-based MOF, Cu[Ni(2,3-pyrazinedithiolate) 2 ] (1), is evaluated as an electrocatalyst for the HER. In pH 1.3 aqueous electrolyte solution, 1 exhibits a catalytic onset at –0.43 V vs the reversible hydrogen electrode (RHE), an overpotential (η 10 mA/cm 2 ) of 0.53 V to reach a current density of 10 mA/cm 2 , and a Tafel slope of 69.0 mV/dec. Interestingly, under controlled potential electrolysis, 1 undergoes an activation process that results in a more active catalyst with a 200 mV reduction in the catalytic onset and η 10 mA/cm 2 . It is proposed that the activation process is a result of the cleavage of Cu–N bonds in the presence of protons and electrons. Furthermore, this hypothesis is supported by various experimental studies and density functional theory calculations.

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

Determining the hydronium pKα at platinum surfaces and the effect on pH-dependent hydrogen evolution reaction kinetics

Electrocatalytic hydrogen evolution reaction (HER) is critical for green hydrogen generation and exhibits distinct pH-dependent kinetics that have been elusive to understand. A molecular-level understanding of the electrochemical interfaces is essential for developing more efficient electrochemical processes. Here we exploit an exclusively surface-specific electrical transport spectroscopy (ETS) approach to probe the Pt-surface water protonation status and experimentally determine the surface hydronium pK a = 4.3. Quantum mechanics (QM) and reactive dynamics using a reactive force field (ReaxFF) molecular dynamics (RMD) calculations confirm the enrichment of hydroniums (H 3 O + * ) near Pt surface and predict a surface hydronium pK a of 2.5 to 4.4, corroborating the experimental results. Importantly, the observed Pt-surface hydronium pK a correlates well with the pH-dependent HER kinetics, with the protonated surface state at lower pH favoring fast Tafel kinetics with a Tafel slope of 30 mV per decade and the deprotonated surface state at higher pH following Volmer-step limited kinetics with a much higher Tafel slope of 120 mV per decade, offering a robust and precise interpretation of the pH-dependent HER kinetics. These insights may help design improved electrocatalysts for renewable energy conversion.

Zhong, Guangyan↗
DOE OSTI2021

Influence of the proton relay spacer on hydrogen electrocatalysis by cobalt hangman porphyrins

A cobalt hangman porphyrin system with a phenyl spacer between the porphyrin ring and an internal carboxylic acid group as well as its non-hangman analogue were synthesized and utilized for the study of the proton-coupled electron transfer (PCET) kinetics attendant to electrocatalytic hydrogen evolution. Cyclic voltammetry (CV) together with simulations show that a short distance between the proton relay and the redox active cobalt center as well as the increased proton donating strength results in superior catalytic activity. Here, the mechanism of hydrogen generation is at the nexus of proton transfer–electron transfer (PTET) and concerted proton–electron transfer (CPET), as opposed to an ETPT mechanism that is characteristic of hangman systems with longer proton relay networks.

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

Design and Synthesis of PtPdNiCoMn High‐Entropy Alloy Electrocatalyst for Enhanced Alkaline Hydrogen Evolution Reaction: A Theoretically Supported Predictive Design Approach

Electrocatalytic hydrogen generation requires a multifunctional electrocatalyst with abundant active sites to drive multielectron transfer reactions. High entropy alloys (HEA) are five or more-elements with high configurational entropy are considered unique materials for next-generation electrocatalysts. Here, in this work, based on new screening guidelines for catalyst selections that combine density-functional theory calculated Gibbs formation-enthalpy with bond length and electronegativity variance, a novel HEA electrocatalyst consisting of five elements, namely, Pt, Pd, Ni, Co, and Mn has been designed. By simple room temperature electrodeposition, the designed catalyst is prepared and its hydrogen evolution reaction (HER) is explored and validated through experimental and theoretical approaches. The HEA demonstrated a superior HER activity with an overpotential of 22.6 mV at -10 mA cm -2 which outperforms Pt/C commercial catalyst. No evident degradation of the material is detected even after 100 hours of continuous operation under high current density. Moreover, the HEA has shown exceptional performance in harsh electrolyte conditions such as in simulated seawater and actual seawater. Remarkably, the density-functional theory calculated Gibbs formation-enthalpy is small (≈0 eV) compared to Pt/C placing the new HEA near the apex of Trasatti's model of Volcano plot, which is also suggestive of superior HER activity.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Oxygen Evolution Reaction in Alkaline Environment: Material Challenges and Solutions

Abstract The oxygen evolution reaction (OER) generally exists in electrochemistry‐enabled applications that are coupled with cathodic reactions like hydrogen evolution, carbon dioxide reduction, ammonia synthesis, and electrocatalytic hydrogenation. The OER heavily impacts the overall energy efficiency of these devices because the sluggish OER kinetics result in a huge overpotential, thus, a large amount of efficient catalysts are needed. The benchmark iridium and ruthenium (Ir/Ru)‐based materials (mostly used in acid media) are, however, significantly limited by their scarcity. Non‐precious metal‐based catalysts (NPMCs) have emerged as the most promising alternatives; however, they tend to degrade quickly under the harsh operating conditions of typical OER devices. Another challenge is the unsatisfying performance of OER catalysts when integrated in real‐world devices. Herein, the OER active sites for three mainstream types of NPMCs including non‐precious transition metal oxides/(oxy)hydroxides, metal‐free carbon materials, and hybrid non‐precious metal and carbon composites are reviewed. In addition, possible degradation mechanisms for active sites and mitigation strategies are discussed in detail. This review also provides insights into the gaps between R&D of NPMCs for the OER and their applications in practical devices.

Xie, Xiaohong↗
DOE OSTI2020

First-principle investigation on catalytic hydrogenation of benzaldehyde over Pt-group metals

We report that understanding the hydrogenation of organic compounds in the aqueous phase has always been fundamentally important for improving carbon neutral pathways to fuels and value-added chemicals. In this study, we investigated both thermodynamic and kinetic profiles of benzaldehyde hydrogenation over the Pd(111) and Pt(111) metal surfaces using density functional theory (DFT) and ab initio molecular dynamic (AIMD) simulations. The adsorption of H 2 shows the mixed preference of H adsorption sites on the Pt(111), while the fcc adsorption site is dominant for H on the Pd(111). When benzaldehyde is added to the systems, we observe a strong reduction of benzaldehyde on charged Pd (111) surface compared with that on neutral surface. In contrast, charged state of the Pt(111) surface does not change their interaction. Subsequent hydrogenation reaction of benzaldehyde over Pd(111), proceeding via Langmuir-Hinshelwood mechanism, is affected by two major factors: the presence of H 2 O solvent and surface charge. The presence of H 2 O solvent greatly reduces the activation energy of C-H and O-H bond formation during the hydrogenation process. Furthermore, the hydrogenation step via C-H bond formation is preferred thermodynamically and kinetically over O-H bond formation during thermocatalytic hydrogenation, while the opposite trend holds true during electrocatalytic hydrogenation.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗