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The world is facing grand challenges in energy security, environmental pollution, and sustainable use (and re‐use) of resources. Electrochemical processes, incorporating electrosynthesis, electrochemical catalysis, and electrochemical energy storage devices, provide pathways to address these challenges via green chemistry. However, the applicability of electrochemical processes for these systems is limited by the required energy input, the "electrons" in electrochemistry. Electrocatalysis as a subset of electrochemistry is set to underpin many of the United Nations Sustainable Development Goals, including "Affordable and Clean Energy" through the production of future fuels and abatement of carbon emissions; "Responsible Consumption and Production" through recycling and degradation of waste; and "Climate Action" through CO2 (and other greenhouse gas) remediation. The rise of green photovoltaic power has lowered the carbon cost of these electrons, making electrocatalysis an even more viable, green(er), chemical conversion pathway. This perspective highlights the need for comprehensive understanding of catalyst structure via in situ and operando analysis to complement device design considerations. The challenges faced by the field of electrocatalysis in data reporting, elimination of electrochemical artifacts, catalyst stability, and scaling to industrial relevance, along with opportunities, emerging tools, are discussed with a view to achieve the maximum 'potential' of electrocatalysis. [ABSTRACT FROM AUTHOR]

We derive a generalized equation that governs the spreading of liquid films under high-frequency (MHz-order) substrate vibration in the form of propagating surface waves and show that this single relationship is universally sufficient to collectively describe the rich and diverse dynamic phenomena recently observed for the transport of oil films under such substrate excitation, in particular, Rayleigh surface acoustic waves. In contrast to low-frequency (Hz- to kHz-order) vibration-induced wetting phenomena, film spreading at such high frequencies arises from convective drift generated by the viscous periodic flow localized in a region characterized by the viscous penetration depth β(-1)≡(2μ/ρω)(1/2) adjacent to the substrate that is invoked directly by its vibration; μ and ρ are the viscosity and the density of the liquid, respectively, and ω is the excitation frequency. This convective drift is responsible for driving the spreading of thin films of thickness h≪k(l)(-1), which spread self-similarly as t(1/4) along the direction of the drift corresponding to the propagation direction of the surface wave, k(l) being the wave number of the compressional acoustic wave that forms in the liquid due to leakage of the surface wave energy from the substrate into the liquid and t the time. Films of greater thicknesses h∼k(l)(-1)≫β(-1), in contrast, are observed to spread with constant velocity but in a direction that opposes the drift and surface wave propagation due to the attenuation of the acoustic wave in the liquid. The universal equation derived allows for the collective prediction of the spreading of these thin and thick films in opposing directions.

A novel strategy utilizing high‐frequency (10 MHz) hybrid sound waves to dramatically enhance hydrogen evolution reactions (HER) in notoriously difficult neutral electrolytes by modifying their network coordination state is presented. Herein, the practical limitations associated with existing electrolyzer technology is addressed, including the need for highly corrosive electrolytes and expensive electrocatalysts, by redefining conceptually‐poor hydrogen electrocatalysts in neutral electrolytes. The improvement in HER performance is attributed to the unique capability of the intense local electromechanical coupling arising from the acoustic‐forcing to 'frustrate' the tetrahedrally‐coordinated hydrogen bond network of water molecules at the electrode–electrolyte interface, resulting in the generation of a high concentration of "free" water molecules that are more readily able to access catalytic sites on the unmodified polycrystalline electrode. Together with the other synergistic effects that accompany the acoustic excitation (e.g., hydronium ion generation, convective relaxation of diffusion mass transfer limitations, and prevention of bubble build‐up and their removal from the electrode), the resultant overpotential reduction of 1.4 V at −100 mA cm−2 and corresponding 14‐fold increase in current density, together with a net‐positive energy saving of 27.3%, showcases the potential of the technology as a scalable platform for effectively enhancing the efficiency of green hydrogen production. [ABSTRACT FROM AUTHOR]

Ultrasound constitutes a powerful means for materials processing. Similarly, a new field has emerged demonstrating the possibility for harnessing sound energy sources at considerably higher frequencies (10 MHz to 1 GHz) compared to conventional ultrasound (⩽3 MHz) for synthesizing and manipulating a variety of bulk, nanoscale, and biological materials. At these frequencies and the typical acoustic intensities employed, cavitation—which underpins most sonochemical or, more broadly, ultrasound‐mediated processes—is largely absent, suggesting that altogether fundamentally different mechanisms are at play. Examples include the crystallization of novel morphologies or highly oriented structures; exfoliation of 2D quantum dots and nanosheets; polymer nanoparticle synthesis and encapsulation; and the possibility for manipulating the bandgap of 2D semiconducting materials or the lipid structure that makes up the cell membrane, the latter resulting in the ability to enhance intracellular molecular uptake. These fascinating examples reveal how the highly nonlinear electromechanical coupling associated with such high‐frequency surface vibration gives rise to a variety of static and dynamic charge generation and transfer effects, in addition to molecular ordering, polarization, and assembly—remarkably, given the vast dimensional separation between the acoustic wavelength and characteristic molecular length scales, or between the MHz‐order excitation frequencies and typical THz‐order molecular vibration frequencies. [ABSTRACT FROM AUTHOR]