A strategy to modulate the electrocatalytic activity of copper towards CO 2 reduction involving adsorption of acrylamide, acrylic acid and allylamine polymers is presented. Modification of electrodeposited copper foam with poly(acrylamide) leads to a significant enhancement in faradaic efficiency for ethylene from 13% (unmodified foam) to 26% at-0.96 V vs. RHE, whereas methane yield is unaffected. Effects from crystalline phase distribution and copper oxide phases are ruled out as the source of enhancement through XPS and in-situ XRD analysis. DFT calculations reveal that poly(acrylamide) adsorbs on the copper surface via the oxygen atom on the carbonyl groups, and enhances ethylene formation by i) charge donation to the copper surface that activates 1

Physical neural networks made of analog resistive switching processors are promising platforms for analog computing. State-of-the-art resistive switches rely on either conductive filament formation or phase change. These processes suffer from poor reproducibility or high energy consumption, respectively. Herein, we demonstrate the behavior of an alternative synapse design that relies on a deterministic charge-controlled mechanism, modulated electrochemically in solid-state. The device operates by shuffling the smallest cation, the proton, in a threeterminal configuration. It has a channel of active material, WO 3. A solid proton reservoir layer, PdH x , also serves as the gate terminal. A proton conducting solid electrolyte separates the channel and the reservoir. By protonation/deprotonation, we modulate the electronic conductivity of the channel over seven orders of magnitude, obtaining a continuum of resistance states. Proton intercalation increases the electronic conductivity of WO 3 by increasing both the carrier density and mobility. This switching mechanism offers low energy dissipation, good reversibility, and high symmetry in programming.

RuO 2 is one of the most active electrocatalysts toward oxygen evolution reaction (OER), but it suffers from rapid dissolution in electrochemical environments. It is also established experimentally that corrosion of metal oxides can, in fact, promote catalytic activity for OER owing to the formation of a surface hydrous amorphous layer. However, the mechanistic interplay between corrosion and OER across metal-oxide catalysts and to what degree these two processes are correlated are still debated. Herein, we employ ab initio molecular dynamics-based blue moon ensemble approach in combination with OER thermodynamic analysis to reveal a clear mechanistic coupling between Ru dissolution and OER at the RuO 2 (110)/water interface. Specifically, we demonstrate that (i) dynamic transitions between metastable dissolution intermediates greatly affect catalytic activity toward OER, (ii) dissolution and OER processes share common intermediates with OER promoting Ru detachment from the surface, (iii) the lattice oxygen can be involved in the OER, and (iv) the coupling between different OER intermediates formed at the same Ru site of the metastable dissolution state can lower the theoretical overpotential of OER down to 0.2 eV. Collectively, our findings illustrate the critical role of highly reactive metastable dissolution intermediates in facilitating OER and underscore the need for the incorporation of interfacial reaction dynamics to resolve apparent conflicts between theoretically predicted and experimentally measured OER overpotentials.

Single-phase multiferroic materials that allow the coexistence of ferroelectric and magnetic ordering above room temperature are highly desirable, motivating an ongoing search for mechanisms for unconventional ferroelectricity in magnetic oxides. Here, we report an antisite defect mechanism for room temperature ferroelectricity in epitaxial thin films of yttrium orthoferrite, YFeO3, a perovskite-structured canted antiferromagnet. A combination of piezoresponse force microscopy, atomically resolved elemental mapping with aberration corrected scanning transmission electron microscopy and density functional theory calculations reveals that the presence of YFe antisite defects facilitates a non-centrosymmetric distortion promoting ferroelectricity. This mechanism is predicted to work analogously for other rare earth orthoferrites, with a dependence of the polarization on the radius of the rare earth cation. Our work uncovers the distinctive role of antisite defects in providing a mechanism for ferroelectricity in a range of magnetic orthoferrites and further augments the functionality of this family of complex oxides for multiferroic applications.

ontrolling the magnetic state of devices by electrical means is critical for spin-based data storage and logic 1,2 . One of the key technological challenges is to achieve efficient 180° magnetic switching by electrical means. Current methods are mostly based on local magnetic fields or spin torques 3,4 . Due to a much lower energy consumption 5,6 , voltage-controlled magnetization switching is desirable. However, it is inherently difficult because electric fields do not induce the required time-reversal symmetry breaking for 180° magnetic switching. Many methods, such as using piezoelectric and multiferroic materials 5,[7][8][9][10][11] , are being explored for voltage-controlled magnetization switching. However, these methods involve either high voltages for inducing enough strain, or difficult fabrication procedures.Multi-sublattice materials present unique opportunities for voltage control of magnetism 12,13 , with ferrimagnets being promising for achieving 180° switching owing to their multi-sublattice configuration with magnetic moments of different magnitudes opposing each other. By tuning the relative sublattice magnetization magnitudes, the net magnetization can be reversed. Moreover, compared with ferromagnets, ferrimagnets offer technological advantages as they allow for small spin textures 14 , fast spin dynamics [14][15][16] and ultrafast optical switching 17 . However, the conventional approaches to controlling the compensation of ferrimagnets, such as varying the composition at fabrication 18 , annealing 19,20 , heating or cooling 21 and hydrogen gas exposure 22,23 , do not allow for localized electrical actuation. Ultrashort light pulses have been shown to enable all-optical switching of ferrimagnets 17,24,25 , however, the need for an ultrafast laser source may complicate device designs and the optical paths may be difficult to scale.Here, we show the reversible control of the dominant sublattice of a rare earth-transition metal (RE-TM) alloy ferrimagnet (GdCo) by a gate voltage (V G ) using a solid-state hydrogen pump 26 . The control originates from the injection of hydrogen, sourced from ambient moisture through hydrolysis, into GdCo, which tunes the relative sublattice magnetizations and hence the degree of compensation. By applying a small V G , the compensation temperature (T M ) can be shifted by >100 K, and the dominant sublattice can be reversibly switched under ambient, isothermal conditions. Element-specific X-ray magnetic circular dichroism (XMCD) revealed that hydrogenation reduces the sublattice magnetization of Gd substantially, but only modestly reduces that of Co. Mean-field modelling of the experimental data combined with ab initio calculations suggest that this results from hydrogen-induced reduction of the inter-sublattice exchange coupling strength that is largely responsible for the Gd sublattice order. We demonstrate here that the dominant sublattice can be toggled using pulses as short as 50 μs at room temperature, and that the devices show no degradation after >10 4 gatin...