Visualization of Electrooxidation on Palladium Single Crystal Surfaces via In Situ Raman Spectroscopy.

The electrooxidation of catalyst surfaces is across various electrocatalytic reactions, directly impacting their activity, stability and selectivity. Precisely characterizing the electrooxidation on well-defined surfaces is essential to understanding electrocatalytic reactions comprehensively. Herein, we employed in situ Raman spectroscopy to monitor the electrooxidation process of palladium single crystal.

Synergistic Modulation of Multiple Sites Boosts Anti-Poisoning Hydrogen Electrooxidation Reaction with Ultrasmall (PtRh)V Ternary Intermetallic Nanoparticles.

Promoting the hydrogen oxidation reaction (HOR) activity and poisoning tolerance of electrocatalysts is crucial for the large-scale application of hydrogen-oxygen fuel cell. However, it is severely hindered by the scaling relations among different intermediates. Herein, lattice-contracted Pt-Rh in ultrasmall ternary L1-(PtRh)V intermetallic nanoparticles (~2.

Molecular understanding of cation effects on double layers and their significance to CO-CO dimerization.

Cation effects have been shown in numerous experiments to play a significant role in electrocatalysis. To understand these effects at the molecular level, we systematically investigate the structures and capacitances of electric double layers with a variety of cations as counter charges at Pt(111)-CO/water interfaces with molecular dynamics. It is encouraging to find that the computed Helmholtz capacitances for different cations are in quantitative agreement with experiments, and that the trend of cation effects on capacitances shows clear correlation with the structures of interface cations of differing sizes and hydration energies.

Revealing the role of interfacial water and key intermediates at ruthenium surfaces in the alkaline hydrogen evolution reaction.

Ruthenium exhibits comparable or even better alkaline hydrogen evolution reaction activity than platinum, however, the mechanistic aspects are yet to be settled, which are elucidated by combining in situ Raman spectroscopy and theoretical calculations herein. We simultaneously capture dynamic spectral evidence of Ru surfaces, interfacial water, *H and *OH intermediates. Ru surfaces exist in different valence states in the reaction potential range, dissociating interfacial water differently and generating two distinct *H, resulting in different activities.

Understanding the Effects of Electrode Material, Single Crystal Facet, and Electrolyte Ion on the Helmholtz Capacitance of Metal/Aqueous Solution Interfaces.

The comprehensive interpretation of the measured differential Helmholtz capacitance curve is vital for advancing our understanding of the interfacial structure. While several possible physical effects contributing to the Helmholtz capacitance have been proposed theoretically, combining those factors to explain the experimentally observed potential-dependent capacitance profile remains a significant challenge. In this study, we employ ab initio molecular dynamics simulations to model various metal/solution interfaces.

Renewable galactomannan-based biogums with structure regulation to protect zinc metal anodes via blocking and confinement effect.

Galactomannan-based biogums were derived from fenugreek, guar, tara, and carob and consisted of mannose and galactose with different ratios, as well as the implementation of high-value utilization was very significant for sustainable development. In this work, renewable and low-cost galactomannan-based biogums were designed and developed as functional coatings protected on the Zn metal anodes. The molecule structure of galactomannan-based biogums were explored on the effect of anticorrosion ability and uniform deposition behavior through the introduction of fenugreek gum, guar gum, tara gum, and carob gum with different ratios of mannose to galactose as 1.

Surface Control Behavior toward Crystal Regulation and Anticorrosion Capacity for Zinc Metal Anodes.

The commercial application of high-safety aqueous zinc (Zn) secondary batteries is hindered by the poor cycling life of Zn metal anodes. Here we propose a dendrite growth and hydrogen evolution corrosion reaction mechanism from the binding energy of the deposited crystal plane on the Zn surface and the adsorption energy of HO molecules on different crystal planes as well as the binding energy of HO molecules with Zn ions. The biomass-based alkyl polyglucoside (APG) surfactant is adopted as an electrolyte additive of 0.

Molecular understanding of the Helmholtz capacitance difference between Cu(100) and graphene electrodes.

Unraveling the origin of Helmholtz capacitance is of paramount importance for understanding the interfacial structure and electrostatic potential distribution of electric double layers (EDL). In this work, we combined the methods of ab initio molecular dynamics and classical molecular dynamics and modeled electrified Cu(100)/electrolyte and graphene/electrolyte interfaces for comparison. It was proposed that the Helmholtz capacitance is composed of three parts connected in series: the usual solvent capacitance, water chemisorption induced capacitance, and Pauling repulsion caused gap capacitance.

Modeling stepped Pt/water interfaces at potential of zero charge with ab initio molecular dynamics.

It is worth understanding the potentials of zero charge (PZCs) and structures of stepped metal/water interfaces, because for many electrocatalytic reactions, stepped surfaces are more active than atomically flat surfaces. Herein, a series of stepped Pt/water interfaces are modeled at different step densities with ab initio molecular dynamics. It is found that the structures of Pt/water interfaces are significantly influenced by the step density, particularly in regard to the distribution of chemisorbed water.

Recent Progress toward Ab Initio Modeling of Electrocatalysis.

Electrode potential is the key factor for controlling electrocatalytic reactions at electrochemical interfaces, and moreover, it is also known that the pH and solutes (e.g., cations) of the solution have prominent effects on electrocatalysis.

Modeling Electrified Pt(111)-H/Water Interfaces from Ab Initio Molecular Dynamics.

Unraveling the atomistic structures of electric double layers (EDL) at electrified interfaces is of paramount importance for understanding the mechanisms of electrocatalytic reactions and rationally designing electrode materials with better performance. Despite numerous efforts dedicated in the past, a molecular level understanding of the EDL is still lacking. Combining the state-of-the-art ab initio molecular dynamics (AIMD) and recently developed computational standard hydrogen electrode (cSHE) method, it is possible to realistically simulate the EDL under well-defined electrochemical conditions.

Linear Correlation between Water Adsorption Energies and Volta Potential Differences for Metal/water Interfaces.

Potential of zero charge (PZC) is an important reference for understanding the interface charge and structure at a given potential, and its difference from the work function of metal surface (Φ) is defined as the Volta potential difference (ΔΦ). In this work, we model 11 metal/water interfaces with ab initio molecular dynamics. Interestingly, we find ΔΦ is linearly correlated with the adsorption energy of water () on the metal surface.

Improving the Electrochemical Property of Silicon Anodes through Hydrogen-Bonding Cross-Linked Thiourea-Based Polymeric Binders.

Binders play a crucial role in the development of silicon (Si) anodes for lithium-ion batteries with high specific energy. The large volume change of Si (∼300%) during repeated discharge and charge processes causes the destruction and separation of electrode materials from the copper (Cu) current collector and ultimately results in poor cycling performance. In the present study, we design and prepare hydrogen-bonding cross-linked thiourea-based polymeric binders (denoted CMC--SN) in consideration of their excellent binding interaction with the Cu current collector and low cost as well.

Molecular origin of negative component of Helmholtz capacitance at electrified Pt(111)/water interface.

Electrified solid/liquid interfaces are the key to many physicochemical processes in a myriad of areas including electrochemistry and colloid science. With tremendous efforts devoted to this topic, it is unexpected that molecular-level understanding of electric double layers is still lacking. Particularly, it is perplexing why compact Helmholtz layers often show bell-shaped differential capacitances on metal electrodes, as this would suggest a negative capacitance in some layer of interface water.

In Situ Raman Study of CO Electrooxidation on Pt(hkl) Single-Crystal Surfaces in Acidic Solution.

The adsorption and electrooxidation of CO molecules at well-defined Pt(hkl) single-crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top- and bridge-site adsorbed CO* molecules on Pt(111) and Pt(100).

Direct Raman Spectroscopic Evidence of Oxygen Reduction Reaction Intermediates at High-Index Pt() Surfaces.

The study of the oxygen reduction reaction (ORR) at high-index Pt() single crystal surfaces has received considerable interest due to their well-ordered, typical atomic structures and superior catalytic activities. However, it is difficult to obtain direct spectral evidence of ORR intermediates during reaction processes, especially at high-index Pt() surfaces. Herein, Raman spectroscopy has been employed to investigate ORR processes at high-index Pt() surfaces containing the [011̅] crystal zone-i.

Early Stages of Electrochemical Oxidation of Cu(111) and Polycrystalline Cu Surfaces Revealed by Raman Spectroscopy.

Investigating the chemical nature of the adsorbed intermediate species on well-defined Cu single crystal substrates is crucial in understanding many electrocatalytic reactions. Herein, we systematically study the early stages of electrochemical oxidation of Cu(111) and polycrystalline Cu surfaces in different pH electrolytes using shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). On Cu(111), for the first time, we identified surface OH species which convert to chemisorbed "O" before forming CuO in alkaline (0.

In situ probing electrified interfacial water structures at atomically flat surfaces.

Solid/liquid interfaces are ubiquitous in nature and knowledge of their atomic-level structure is essential in elucidating many phenomena in chemistry, physics, materials science and Earth science. In electrochemistry, in particular, the detailed structure of interfacial water, such as the orientation and hydrogen-bonding network in electric double layers under bias potentials, has a significant impact on the electrochemical performances of electrode materials. To elucidate the structures of electric double layers at electrochemical interfaces, we combine in situ Raman spectroscopy and ab initio molecular dynamics and distinguish two structural transitions of interfacial water at electrified Au single-crystal electrode surfaces.