Hydrogen is poised to play a key role in the energy transition by decarbonizing hard-to-electrify sectors and enabling the storage, transport, and trade of renewable energy. Recent forecasts project a thousand-fold expansion of global water electrolysis capacity as early as 2030. In this context, several electrolysis technologies are likely to coexist in the market, each catering to different applications and geographies. They face the common challenge of decreasing the cost of hydrogen produced, for which energy efficiency is a major but not the only factor. In this Perspective, we dispel common misconceptionsrooted in outdated designsaround alkaline water electrolysis and offer an overview of the main technical pathways to reduce the cost of hydrogen from modern systems already under commercialization. By identifying key research needs, we aim to motivate work into overlooked areas that both offer interesting scientific questions and can contribute to the gigawatt-scale production of green hydrogen in the short- to medium-term.

We present a joint theoretical−experimental study of CO coverage and facet selectivity on Au under electrochemical conditions. With in situ attenuated total reflection surface-enhanced IR spectroscopy, we investigate the CO binding in an electrochemical environment. At 0.2 V versus SHE, we detect a CO band that disappears upon facet-selective partial Pb underpotential deposition (UPD), suggesting that Pb blocks certain CO adsorption sites. With Pb UPD on single crystals and theoretical surface Pourbaix analysis, we eliminate (111) terraces as a possible adsorption site of CO. Ab initio molecular dynamics simulations of explicit water on the Au surface show the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace than (211) steps in an electrochemical environment, even though Au steps under gas-phase conditions bind CO* more strongly. The competition between water and CO adsorption can result in different binding sites for CO* on Au in the gas phase and electrochemical environments.

We consider the motion of an electromagnetic vibrational energy harvester (EMVEH) as function of the initial position and velocity and show that this displays a classical chaotic dynamical behavior. The EMVEH considered consists of three coaxial cylindrical permanent magnets and two coaxial coils. The polarities of the three magnets are chosen in such a way that the central magnet floats, with its lateral motion being prevented by enclosion in a hollow plastic tube. The motion of the floating magnet, caused by e.g. environmental vibrations, induces a current in the coils allowing electrical energy to be harvested. We analyze the behavior of the system using a numerical model employing experimentally verified expressions of the force between the magnets and the damping force between the floating magnet and the coils. We map out the phase space of the motion of the system with and without gravity, and show that this displays a fractal-like behavior and that certain driving frequencies and initial conditions allow a large power to be harvested, and that more stable states than two exists. Finally, we show that at leasts fifth order polynomial approximation is necessary to approximate the magnet-magnet force and correctly predict the system behavior.

<div> <div> <div> <p>We present a joint theoretical-experimental study of CO coverage on Au under both gas phase and electrochemical conditions. By analyzing temperature programmed desorption (TPD) spectra on (211) and (310) surface facets, we show that, under atmospheric CO pressure, the steps of both facets adsorb up to 0.7 ML coverage of *CO, while the terraces have close to zero coverage. We show this result to be consistent with density functional theory calculations of adsorption energies. Under electrochemical conditions on polycrystalline Au, we investigate the CO binding with in situ attenuated total reflection surface enhanced IR spectra (ATR-SEIRAS). We detect a CO band at 0.2V vs. SHE that disappears upon partial Pb underpotential deposition (facet selective), which suggests Pb blocks the CO adsorption sites. With Pb underpotential deposition on single crystals and theoretical surface Pourbaix analysis, we narrow down the possible adsorption sites of CO to open site motifs: (211) and (110) steps, as well as (100) terraces. Ab initio molecular dynamics simulations of explicit water at the Au surface, however, shows the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace than steps in an electrochemical environment. The competition between water and CO adsorption can result in different binding sites for *CO on Au in gas phase and electrochemical environments. </p> </div> </div> </div>

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