Determining the adsorption energies of small molecules with the intrinsic properties of adsorbates and substrates

Utilizing the Broad Electromagnetic Spectrum and Unique Nanoscale Properties for Chemical-Free Water Treatment

Clean water is critical for drinking, industrial processes, and aquatic organisms. Existing water treatment and infrastructure are chemically-intensive and based on nearly century-old technologies that fail to meet modern large and decentralized communities. The next-generation of water processes can transition from outdated technologies by utilizing nanomaterials to harness energy from across the electromagnetic spectrum, enabling electrified and solar-based technologies. The last decade was marked by tremendous improvements in nanomaterial design, synthesis, characterization, and assessment of material properties. Realizing the benefits of these advances requires placing greater attention on embedding nanomaterials onto and into surfaces within reactors and applying external energy sources. This will allow nanomaterial-based processes to replace Victorian-aged, chemical intensive water treatment technologies.

Tunable band gaps and high carrier mobilities in stanene by small organic molecule adsorption under external electric fields

The effects of small organic molecule (SOM) adsorption with benzene (C6H6), hexafluorobenzene (C6F6), and p-difluorobenzene (C6H4F2) on the electronic properties of stanene under external electric fields are investigated through first-principles calculations. Different adsorption sites and molecular orientations are considered to determine the most stable configurations of small organic molecule (SOM) adsorption on the surface of stanene. The results show that the internal electric field caused by the adsorption of small organic molecules destroys the symmetry of the two sublattices of stanene in C6H6/stanene, C6F6/stanene and C6H4F2/stanene systems with the most stable configurations, opening the band gaps of stanene with 39.5, 18.9 and 14.5 meV, respectively. Under an external electric field, a wide range of linearly tunable and sizable direct band gaps (31.6-420.1 meV for the C6H6/stanene system, 14.8-587.2 meV for the C6F6/stanene system and 14.5-490.2 meV for the C6H4F2/stanene system) are merely determined by the strength of the composite electric field despite its direction. The mechanism of charge transfer between stanene and organic molecules under an external electric field can be revealed using an equivalent capacitor model to explain the tunable charge transfer. More importantly, the high carrier mobility of the stable SOM/stanene systems under an external electric field is largely retained due to the weak interactions at the interface. These results indicate that the electronic properties of stanene can be effectively modulated by the surface adsorption of organic molecules under an external electric field, providing effective and reversible routes to enhance the performance of stanene for novel electronic devices in the future.

Defects in ferroelectric HfO2

The discovery of ferroelectricity in polycrystalline thin films of doped HfO2 has reignited the expectations of developing competitive ferroelectric non-volatile memory devices. To date, it is widely accepted that the performance of HfO2-based ferroelectric devices during their life cycle is critically dependent on the presence of point defects as well as structural phase polymorphism, which mainly originates from defects either. The purpose of this review article is to overview the impact of defects in ferroelectric HfO2 on its functional properties and the resulting performance of memory devices. Starting from the brief summary of defects in classical perovskite ferroelectrics, we then introduce the known types of point defects in dielectric HfO2 thin films. Further, we discuss main analytical techniques used to characterize the concentration and distribution of defects in doped ferroelectric HfO2 thin films as well as at their interfaces with electrodes. The main part of the review is devoted to the recent experimental studies reporting the impact of defects in ferroelectric HfO2 structures on the performance of different memory devices. We end up with the summary and perspectives of HfO2-based ferroelectric competitive non-volatile memory devices.

High-Throughput Screening of a Single-Atom Alloy for Electroreduction of Dinitrogen to Ammonia

Exploring electrocatalysts with high activity, selectivity, and stability is essential for the development of applicable electrocatalytic ammonia synthesis technology. By performing density functional theory calculations, we systematically investigated the potential of a series of transition-metal-doped Au-based single-atom alloys (SAAs) as promising electrocatalysts for nitrogen reduction reaction (NRR). The overall process for the Au-based electrocatalyst suffers from the limiting potential arising from the first hydrogenation step of the reduction of *N₂ to *NNH. However, SAAs showed to be favorable toward lowering free energy barriers by increasing the binding strength of N₂. According to simulation results, three descriptors were proposed to describe the first hydrogenation step ΔG(*N₂ → *NNH): ΔG(*NNH), d-band center, and d/√E_m. Eight doped elements (Ti, V, Nb, Ru, Ta, Os, W, and Mo) were initially screened out with a limiting potential ranging from -0.75 to -0.30 V. Particularly, Mo- and W-doped systems possess the best activity with a limiting potential of -0.30 V each. Then, the intrinsic relationship between the structure and potential performance was analyzed using machine learning. The selectivity, feasibility, and stability of these candidates were also evaluated, confirming that SAA containing Mo, Ru, Ta, and W could be outstanding NRR electrocatalysts. This work not only broadens our understanding of SAA application in electrocatalysis, but also leads to the discovery of novel NRR electrocatalysts.

Electrodeposition of hybrid nanosheet-structured NiCo2O4 on carbon fiber paper as a non-noble electrocatalyst for efficient electrooxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Hybrid nanosheet-structured NiCo₂O₄ on CFP as a self-supporting electrode for electrochemical oxidation of HMF to FDCA.

Rational catalyst design for CO oxidation: a gradient-based optimization strategy

In this work, we proposed a gradient-based optimization strategy for rational catalyst design.

An Overview of Molecular Dynamic Simulation for Corrosion Inhibition of Ferrous Metals

Molecular dynamics (MD) simulation is a powerful tool to study the molecular level working mechanism of corrosion inhibitors in mitigating corrosion. In the past decades, MD simulation has emerged as an instrument to investigate the interactions at the interface between the inhibitor molecule and the metal surface. Combined with experimental measurement, theoretical examination from MD simulation delivers useful information on the adsorption ability and orientation of the molecule on the surface. It relates the microscopic characteristics to the macroscopic properties which enables researchers to develop high performance inhibitors. Although there has been vast growth in the number of studies that use molecular dynamic evaluation, there is still lack of comprehensive review specifically for corrosion inhibition of organic inhibitors on ferrous metal in acidic solution. Much uncertainty still exists on the approaches and steps in performing MD simulation for corrosion system. This paper reviews the basic principle of MD simulation along with methods, selection of parameters, expected result such as adsorption energy, binding energy and inhibitor orientation, and recent publications in corrosion inhibition studies.

Enhanced Fenton-like Oxidation of As(III) over Ce-Ti Binary Oxide: A New Strategy to Tune Catalytic Activity via Balancing Bimolecular Adsorption Energies

The development of catalysts for oxidation of aqueous contaminants has long been relying on trial-and-error strategies due to lack of activity-tuning principles. Herein, Fenton-like oxidation of As(III) as a chemisorbed model contaminant over a series of fabricated Ce_xTi_1-xO₂ catalysts with tunable structures was investigated. The activity of Ce_xTi_1-xO₂ showed a volcano-shape dependency on Ce molar fraction, peaking at Ce_0.25Ti_0.75O₂ (x = 0.25) with 6.32-6.36 times higher activity and 2.67-2.94 times higher specific activity compared with CeO₂ and TiO₂. The non-radical surface hydroperoxo complexes were experimentally substantiated as the dominant oxidant species on Ce_0.25Ti_0.75O₂, which enabled a high efficiency of H₂O₂ utilization (99.1%). Under the verified Langmuir-Hinshelwood mechanism, the microkinetic model for the catalytic oxidation was established, and thus, the quantitative relationship between activity and adsorption energies for bimolecular chemisorption reactions was elucidated. Theoretically, a catalyst with identical adsorption energies toward both chemisorbed reactants tends to obtain the highest activity. Through DFT calculation, the highest activity of Ce_0.25Ti_0.75O₂ was rationally interpreted by the balanced adsorption energies toward As(III) and H₂O₂, which was attributed to the shifted electronic density of states induced by Ce doping. This study provides a potent strategy to tune the catalytic activity of bimolecular chemisorption reactions.