No abstract

Electrochemical CO2 or CO reduction to high-value C2+ liquid fuels is desirable, but its practical application is challenged by impurities from cogenerated liquid products and solutes in liquid electrolytes, which necessitates cost- and energy-intensive downstream separation processes. By coupling rational designs in a Cu catalyst and porous solid electrolyte (PSE) reactor, here we demonstrate a direct and continuous generation of pure acetic acid solutions via electrochemical CO reduction. With optimized edge-to-surface ratio, the Cu nanocube catalyst presents an unprecedented acetate performance in neutral pH with other liquid products greatly suppressed, delivering a maximal acetate Faradaic efficiency of 43%, partial current of 200 mA⋅cm−2, ultrahigh relative purity of up to 98 wt%, and excellent stability of over 150 h continuous operation. Density functional theory simulations reveal the role of stepped sites along the cube edge in promoting the acetate pathway. Additionally, a PSE layer, other than a conventional liquid electrolyte, was designed to separate cathode and anode for efficient ion conductions, while not introducing any impurity ions into generated liquid fuels. Pure acetic acid solutions, with concentrations up to 2 wt% (0.33 M), can be continuously produced by employing the acetate-selective Cu catalyst in our PSE reactor.

Ferroelectrics have been demonstrated as excellent building blocks for highperformance nonvolatile memories, including memristors, which play critical roles in the hardware implementation of artificial synapses and in-memory computing. Here, it is reported that the emerging van der Waals ferroelectric α-In 2 Se 3 can be used to successfully implement heterosynaptic plasticity (a fundamental but rarely emulated synaptic form) and achieve a resistanceswitching ratio of heterosynaptic memristors above 10 3 , which is two orders of magnitude larger than that in other similar devices. The polarization change of ferroelectric α-In 2 Se 3 channel is responsible for the resistance switching at various paired terminals. The third terminal of α-In 2 Se 3 memristors exhibits nonvolatile control over channel current at a picoampere level, endowing the devices with picojoule read-energy consumption to emulate the associative heterosynaptic learning. The simulation proves that both supervised and unsupervised learning manners can be implemented in α-In 2 Se 3 neutral networks with high image recognition accuracy. Moreover, these heterosynaptic devices can naturally realize Boolean logic without an additional circuit component. The results suggest that van der Waals ferroelectrics hold great potential for applications in complex, energy-efficient, brain-inspired computing systems and logic-in-memory computers.

We show that voltage offsets in the polarization-voltage characteristics of Pb(Zr, Ti)O3 capacitors can lead to imprint in ferroelectric memory devices. The thermal-induced voltage shifts (internal bias field) are in part attributed to the role of oxygen vacancy-related defect dipoles throughout the film. In support of this, it is found that donor doping at the Ti(Zr) sites reduces the thermally-induced voltage shifts. The stress-induced voltage shifts are found to be dependent on the Zr/Ti cation ratio. This compositional dependence is explained by considering the role of deep bulk Ti3+ centers and/or a compositional dependent oxygen vacancy density.

We have developed a simple and rapid method for the synthesis of a precursor solution used in the production of SBT powders and thin films of the layered-perovskite phase SrBi2Ta2O9 (SBT). Precursor solution preparation takes less than 30 min and involves the generation of two solutions: (a) Bi(O2CMe)3 dissolved in pyridine and (b) Ta(OCH2Me)5 added to Sr(O2CMe)2 and then solubilized by HO2CMe. After stirring separately for 10 min, these solutions are combined, stirred for an additional 10 min, and used without any further modifications. The individual solutions and ternary mixture were studied using a variety of analytical techniques. Films of the layered-perovskite phase were formed at temperatures as low as 700 °C. Ferroelectric testing of SBT films, fired at 750 °C, reveals standard hysteresis loops with no fatigue for up to 4 × 109 cycles.