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Advances in microelectronics have led to the development of on-chip intelligent microsystems that can digitalize the physical world, offering functions of sensing, data communication, and intelligent response to stimuli. Either mismatched form factors or limited energy density of available batteries compromises their integration. We report a microimprint fabrication for on-chip Zn−air microbatteries, which bypasses the complication of the catalyst incorporation on the chip at a target position. The on-chip integration of a bifunctional catalyst covalent organic framework with cobalt catalytic unitsenables the onchip Zn−air microbattery to outperform the Zn−air primary cell, showing 3 times more volumetric energy density. It is wirelessly chargeable, and its lifetime capacity is around twice longer than that for commercially available on-chip lithium ion microbatteries. The on-chip Zn−air microbattery can drive various electronic systems. Our approach bridges a long-standing gulf between advanced materials synthesis and their on-chip integration and paves the way toward high-performance on-chip Zn−air batteries.

The monosaccharides glucose, fructose, and xylose were subjected to hydrothermal carbonization in aqueous solution at temperatures of 180, 220, and 250 °C for different operating times (30 min to 16 h). Here, 68% to 78% of the organic carbon was converted into hydrochar at 220 °C with glucose and fructose as feedstock, whereas hydrothermal treatment of xylose did not result in significant hydrochar formation under these conditions. The main topic of this contribution was the identification of stable organic products in the process water in the molecular mass range between 120 and 300 Da by means of GC-MS analysis using several derivatization agents. Special attention was paid to polar OH- and COOH-functionalized compounds. The overwhelming majority of identified organic compounds had cyclic structures of which a prominent group included hydroxylated benzofurans. However, the combined yield of products, which might be potential substrates for liquid biofuels, turned out very low.

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Process water reuse was exercised in the hydrothermal carbonization (HTC) of paper at 200 °C for 16 h, four times. Results showed that hydrochar mass yields increased significantly in the first recirculation step but only slightly in further steps. At the same time, solid carbon content did not increase, and a constant organic carbon distribution between the three product streams, hydrochar, process water (PW), and gas phase, was observed over all recycling steps. Dissolved organic carbon content (DOC) and chemical oxygen demand (COD) of the PWs increased, as well as total acids content, among those specifically lactic, acetic, formic, and propionic acid. Surprisingly, the aerobic biodegradability of the PWs decreased as indicated by lower biochemical to chemical oxygen demand (BOD/COD) ratios in reused process waters. Subsequent methanogenesis of the PW revealed that a high amount of biogas was produced; however, no increase was seen with each recirculation step.

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