Cui Ruopeng,Li Yi,Zhang Xuefei,Duan Zewen,Zhao Biao,Wan Chunlei
Integrating 2D (semi)metals and semiconductors into atomic-scale Schottky heterojunctions offers a promising pathway for achieving robust charge separation, crucial for microwave absorbers, electromagnetic interference shielding materials, electrocatalysts, photocatalysts, etc. However, conventional bottom-up assembly approaches often encounter challenges of severe agglomeration of 2D components and non-basal contacts due to lattice mismatch, resulting in a suboptimal interfacial density and insufficient charge separation. This study introduces a top-down approach involving the thermal deintercalation of graphene/alkylamine superlattices, leading to the in-situ formation of Schottky heterojunctions between the thermally reduced p-type rGO-alkylamine superlattice phase and entirely deintercalated semimetallic rGO phase (rGO denotes reduced graphene oxide), which can be flexibly tuned by the length of the alkylamines. A spatial network of 2D/2D vertical/lateral Schottky heterojunctions is thus formed with high interfacial density, greatly facilitating charge separation, and thereby strengthening polarization loss while reducing conduction loss. This ensures steady permittivity in the Ku band, maintaining strong absorption under small oblique incidence. Accordingly, a record-high simulated far-field bistatic radar cross-section reduction of 72.68 dB at 1° is attained along with diversified adaptive multifunctionality. This paper provides a groundbreaking avenue realizing spatially distributed atomic-scale 2D/2D Schottky heterojunctions in 2D materials, promoting various related functional materials.
Dan Han,Mao-Sheng Cao,Na Li,Dong-Mei She,Wei-Li Song,Haosen Chen,Shuqiang Jiao,Daining Fang
Main observation and conclusion Graphitic materials with intercalated sites are considered as the mostly used positive electrode materials in nonaqueous Al batteries. Unlike the small-size cations, the intercalation/de-intercalation of large-size anions into/out of graphite would induce large volume expansion and micro-structure reconfiguration, leading to unexpected coulombic efficiency in the full cells (<95% within initial several cycles). For understanding the irreversible processes induced by anion intercalation/de-intercalation (AlCl 4 – ), here the kinetics of first two cycles for the Al-graphite batteries have been systematically studied. To study kinetics behaviors at representative states, a combined method upon galvanostatic intermittent titration technique and electrochemical impedance spectroscopy has been carried out. The achieved diffusion coefficients of the positive electrodes assembled with different graphite sizes suggest that size effect also plays a critical role in determining the electrochemical kinetics in the mass transport in both electrolyte and graphitic layers as well as in interface reaction. The morphologies and micro-structures of the post-cycled graphite electrodes have been also experimentally studied, which also well supports the irreversible intercalation/de-intercalation behaviors in graphite electrodes. The results offer a significant platform to well understand the essential factors in tailoring coulombic efficiency from a kinetic view, which would be helpful in promoting the graphite electrodes in Al batteries.
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