Waste printed circuit boards(WPCBs)are hazardous solid wastes that are composed of various metal and non-metal materials.Pyrolysis has long been regarded as an environmentally friendly and promising application techno...Waste printed circuit boards(WPCBs)are hazardous solid wastes that are composed of various metal and non-metal materials.Pyrolysis has long been regarded as an environmentally friendly and promising application technology for recovering organic and inorganic materials from the WPCBs.The pyrolysis atmosphere and co-existing materials are critical factors that significantly influence the pyrolysis behavior.To compare the specific effects of these factors on the pyrolysis characteristics of the WPCBs,a series of thermogravimetric and kinetics analyses has been conducted.It was then found that the apparent activation energy was reduced when pyrolyzed in CO_(2)or co-pyrolyzed with glass fibers,which was supposed to result from the enhanced diffusion and phase boundary reactions.In contrast,an increase in the apparent activation energy was observed at the early stage of the co-pyrolysis with Cu,which was inferred to be associated with the Cu-catalyzed cross-linking effects.Specifically,the formed coke might adsorb pyrolysis products and inhibit the diffusion and reduce the reactive phase boundary.Previous studies have primarily focused on the catalysis of metals in the pyrolysis of WPCBs,while other interactions as well as the kinetic effects of glass fibers and pyrolysis atmospheres have received less discussion.The study presented a comprehensive investigation of the roles played by the pyrolysis atmosphere and co-existing materials in the pyrolysis of the WPCBs.It showed that these factors could alter the reaction-controlling mechanisms by complex interactions.These findings can provide new mechanistic insights and contribute to the use and optimization of pyrolysis-based recycling technologies.展开更多
Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approa...Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approach to engineering the coordination environment of M-N-C(M=Fe,Co,and Ni)SACs by using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator.Compared with that in N2,NH3 was able to promote the doping of N at 7<700℃yet etch the N-species at higher temperatures,by which the M-N coordination number(CN)and the electronic structure were delicately tuned.It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN.As a consequence,the capability of Ni-N-C to dissociate H2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved.Moreover,this modulation method could be applied to other transition metals including Fe and Co.In particular,the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h~1 with 99%selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene,which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts,demonstrating the great potential of engineering the coordination environment of SACs.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52270132 and U20A20273).
文摘Waste printed circuit boards(WPCBs)are hazardous solid wastes that are composed of various metal and non-metal materials.Pyrolysis has long been regarded as an environmentally friendly and promising application technology for recovering organic and inorganic materials from the WPCBs.The pyrolysis atmosphere and co-existing materials are critical factors that significantly influence the pyrolysis behavior.To compare the specific effects of these factors on the pyrolysis characteristics of the WPCBs,a series of thermogravimetric and kinetics analyses has been conducted.It was then found that the apparent activation energy was reduced when pyrolyzed in CO_(2)or co-pyrolyzed with glass fibers,which was supposed to result from the enhanced diffusion and phase boundary reactions.In contrast,an increase in the apparent activation energy was observed at the early stage of the co-pyrolysis with Cu,which was inferred to be associated with the Cu-catalyzed cross-linking effects.Specifically,the formed coke might adsorb pyrolysis products and inhibit the diffusion and reduce the reactive phase boundary.Previous studies have primarily focused on the catalysis of metals in the pyrolysis of WPCBs,while other interactions as well as the kinetic effects of glass fibers and pyrolysis atmospheres have received less discussion.The study presented a comprehensive investigation of the roles played by the pyrolysis atmosphere and co-existing materials in the pyrolysis of the WPCBs.It showed that these factors could alter the reaction-controlling mechanisms by complex interactions.These findings can provide new mechanistic insights and contribute to the use and optimization of pyrolysis-based recycling technologies.
基金supported by the National Key Technology R&D Program of China(No.2020YFA0710202)the National Natural Science Foundation of China(Nos.U1662130,21690080,21690084,and 21721004)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17020100)。
文摘Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approach to engineering the coordination environment of M-N-C(M=Fe,Co,and Ni)SACs by using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator.Compared with that in N2,NH3 was able to promote the doping of N at 7<700℃yet etch the N-species at higher temperatures,by which the M-N coordination number(CN)and the electronic structure were delicately tuned.It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN.As a consequence,the capability of Ni-N-C to dissociate H2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved.Moreover,this modulation method could be applied to other transition metals including Fe and Co.In particular,the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h~1 with 99%selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene,which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts,demonstrating the great potential of engineering the coordination environment of SACs.
