The electrochemical reduction of carbon dioxide (CO 2 ) is investigated in acetonitrile with tetrabutylammonium perchlorate as an electrolyte using a lead cathode and a sacrificial zinc anode, and the product under such a setup is insoluble zinc oxalate at potentials between −2.2 and −2.8 V vs. Ag rod electrode. Preelectrolysis is an effective method to remove the water in the electrolyte, which makes a distinct reduction peak of CO 2 appear at −2.6 V vs. Ag on cyclic voltammogram. Even trace amounts of water in the electrolyte can interfere with the faradaic efficiency of reduction of CO 2 to oxalate, and the product could be β-ZnC 2 O 4 (in anhydrous solution) or ZnC 2 O 4 · 2H 2 O (if water exists). The faradaic efficiency for oxalate production also depends on the cathode potential and the temperature, and the maximum is 96.8 % at −2.6 V vs. Ag and 5 °C. This is the highest value of CO 2 electrochemical reduction found in the literature under ambient pressure.
Carbon-based perovskite solar cells (PSCs) have attracted attention as low-cost and facile fabrication process. However, the ionic nature of perovskite and nonradiative recombination at perovskite/carbon interface are present inevitable obstacles in approaching their highly efficiency. Herein, the multifunctional molecules of zinc oxalate is implanted into the precursor of perovskite to passivate defects and narrowing the interface energy barrier, and a flexible method of screen-printing employed in prepare stacked structure device ITO/SnO 2 /CsPbBr 3 •x % ZnOX //CQDs/ITO. In this regard, CQDs are used as carbon electrodes to replace expensive materials of hole transport layer and precious metal electrode, in which CQDs extracted from sugarcane molasses, a cheap by-product of native sugar industry. Additionally, the stacked structure composed of a photoanode (ITO/SnO 2 /CsPbBr 3 •x % ZnOX) and back electrode (CQDs/ITO) exhibits a promising prospect in photovoltaic application. Finally, the power conversion efficiency of 2 % ZnOX modified PSCs increases to 1.96 %, and the improvement rate has reached 1.54 times. In addition, modified PSCs with a greater stability compared with that of the control device. This work presents a useful approach to passivate defects and provides a cost-effective option to fabricate devices with stacked structure.
Nitrogen-doped porous carbons have emerged as promising electrode materials for supercapacitors. However, the precise control of carbon geometry and the effective doping method remain challenging. Herein, a confined self-assembly template and in-situ mild activation strategy is proposed to prepare cubic lignin composite precursor, followed by co-pyrolysis with melamine at a high temperature for nitrogen-doped hierarchical porous carbons (N-HPLCs). The zinc oxalate template has the coupling effect of confinement and mild activation during carbonization, which not only prevents the restacking of the carbon matrix but also generates zinc cyanamide intermediate to avoid excessive loss of nitrogen species. The optimized N-HPLCs exhibit an accordion-like framework with interconnected porous sheets, ultrahigh edge-nitrogen doping level (up to 12.20 at.%), and a total nitrogen doping level of 14.09 at.%. Consequently, it shows a high gravimetric capacitance of 354 F/g at 0.2 A/g, an extraordinary surface-area-normalized capacitance of 82.1 ± 0.2 μF/cm 2 , and good rate capability in supercapacitor applications. Moreover, the fabricated coin-type symmetric supercapacitor displays a high energy density of 12.9 Wh/kg at 161.9 W/kg and superior cycling stability with a 99.5% capacitance retention after 16,000 cycles at 2.0 A/g. This work offers a novel method for preparing nitrogen-enriched lignin-derived carbon for high-performance supercapacitors.
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