Structural Dynamics of the Electrical Double Layer during Capacitive Charging/Discharging Processes

Transitional structures of Cs⁺ at the outer Helmholtz plane (OHP) have been determined using time-resolved X-ray diffraction during the double-layer charging/discharging on the Ag(100) electrode in CsBr solution. At the double-layer potential region at which c(2 × 2)-Br is formed on Ag(100), the transient current comprises two exponential terms with different time scales: a rapid and a slow one are due to the dielectric polarization of water molecules and the transfer of Cs⁺, respectively. The slow term is composed of different dynamic processes of Cs⁺ during charging and discharging. When the potential is stepped in the positive direction, the coverage of Cs⁺ at the OHP decreases. In this step, the transient X-ray intensity at the (0 0 1) reflection, which is sensitive to the OHP structure, shows that Cs⁺ is released from the OHP according to exponential function of time. The decay of transient intensity of X-ray has a time scale similar to that of the current transient measurement. On the other hand, the accumulation process of Cs⁺ from the diffuse double layer to the OHP comprises two different kinetic processes after a potential step in the negative direction: a rapid one is the accumulation of Cs⁺ near the outer layer, and a slow one is the structural stabilization of the Cs⁺ layer

Air/Liquid Interfacial Nanoassembly of Molecular Building Blocks into Preferentially Oriented Porous Organic Nanosheet Crystals <i>via</i> Hydrogen Bonding

Nanosheets with highly regulated nanopores are ultimately thin functional materials for diverse applications including molecular separation and detection, catalysis, and energy conversion and storage. However, their availability has hitherto been restricted to layered parent materials, covalently bonded sheets, which are layered <i>via</i> relatively weak electrostatic interactions. Here, we report a rational bottom-up methodology that enables nanosheet creation beyond the layered systems. We employ the air/liquid interface to assemble a triphenylbenzene derivative into perfectly oriented highly crystalline noncovalent-bonded organic nanosheets under ambient conditions. Each molecular building unit connects laterally by hydrogen bonding, endowing the nanosheets with size- and position-regulated permanent nanoporosity, as established by <i>in situ</i> synchrotron X-ray surface crystallography and gas sorption measurements. Notably, the nanosheets are constructed specifically by interfacial synthesis, which suppresses the intrinsic complex interpenetrated structure of the bulk crystal. Moreover, they possess exceptional long-term and thermal stability and are easily transferrable to numerous substrates without loss of structural integrity. Our work shows the power of interfacial synthesis using a suitably chosen molecular component to create two-dimensional (2D) nanoassemblies not accessible by conventional bulk crystal exfoliation techniques