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14. Tailoring the Desorption Behavior of Hygroscopic Gels for Atmospheric Water Harvesting in Arid Climates

Author

Lu, Hengyi, Shi, Wen, Zhang, James H., Chen, Amylynn C., Guan, Weixin, Lei, Chuxin, Greer, Julia R., Boriskina, Svetlana V., Yu, Guihua, Lu, Hengyi, Shi, Wen, Zhang, James H., Chen, Amylynn C., Guan, Weixin, Lei, Chuxin, Greer, Julia R., Boriskina, Svetlana V., and Yu, Guihua

Abstract

The ubiquitous nature of atmospheric moisture makes it a significant water resource available at any geographical location. Atmospheric water harvesting (AWH) technology, which extracts moisture from ambient air to generate clean water, is a promising strategy to realize decentralized water production. The high water uptake exhibited by salt-based sorbents makes them attractive for AWH, especially in low relative humidity (RH) environments. Salt-based sorbents often have relatively high desorption heat, rendering water release an energy-intensive process. We proposed a hygroscopic gel, PAM hydrogel controlled incorporated with LiCl, capable of effective moisture harvesting from arid environments. The interactions between the hydrophilic hydrogel network and the captured water enable the PAM-LiCl to accumulate more free and weakly-bonded water molecules, significantly lowering the desorption heat compared with conventional neat salt sorbents. Benefiting from the affinity for swelling of the polymer backbones, the developed PAM-LiCl achieves a high water uptake of ca. 1.1 g/g at 20% RH with fast sorption kinetics of ca. 0.008 g g⁻¹ min⁻¹ and further demonstrates a daily water yield up to ca. 7 g/g at this condition. These findings provide a new pathway for synthesis of materials with efficient water absorption/desorption properties, to reach energy-efficient water release for AWH in arid climates.

Published
2022

40. Reaction Packaging CoSe2Nanoparticles in N-Doped Carbon Polyhedra with Bifunctionality for Overall Water Splitting

Author

Lu, Hengyi, Zhang, Youfang, Huang, Yunpeng, Zhang, Chao, and Liu, Tianxi

Abstract

Water electrolysis is a promising approach for green and large-scale hydrogen production; however, there are still challenges for developing efficient and stable bifunctional electrocatalysts toward the hydrogen and oxygen evolution reactions. Herein, zeolitic imidazolate framework-67 was used as the precursor for the construction of CoSe2nanoparticles trapped in N-doped carbon (NC) polyhedra. Among as-obtained CoSe2-NC hybrid, highly active CoSe2nanoparticles in sizes of 10–20 nm are encapsulated in N-doped few-layer carbon shell, avoiding their easy aggregations of CoSe2nanoparticles as well as enhancing the long-term stability. The unique nanostructured CoSe2-NC hybrid with a hierarchical porosity and 3D conductive framework thus fully exerts outstanding bifunctional catalytic activity of CoSe2centers. As a result, the CoSe2-NC hybrid as bifunctional catalysts for overall water splitting delivers a high current density of 50 mA cm–2with an applied voltage of ∼1.73 V in an alkaline electrolyte, with a promising stability over 50 000 s.

Published
2019
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46. In Situ Growth of Co3O4 Nanoparticles on Interconnected Nitrogen‐Doped Graphene Nanoribbons as Efficient Oxygen Reduction Reaction Catalyst.

Author

Lu, Hengyi, Yan, Jiajie, Zhang, Youfang, Huang, Yunpeng, Gao, Wei, Fan, Wei, and Liu, Tianxi

Subjects
NANORIBBONS, NITROGEN, OXYGEN reduction, FUEL cells, CATALYTIC doping
Abstract

Abstract: A simple, low cost and nontoxic preparation method to obtain high performance oxygen reduction reaction (ORR) catalysts is of great significance in fuel cell fields. Herein, graphene nanoribbons (GNRs) with numerous graphitic edges are chosen as supporting material to hybridize with nitrogen atoms and cobalt oxide (Co3O4) through a simple one‐step hydrothermal reaction. With a high edge‐to‐plane ratio, the GNR sheets could increase the accessibility of N‐atom doping into the graphene edges to form active ORR sites, and be also interconnected with each other to form a conductive network, thus facilitating the fast electron transfer. The intimate contacts between Co3O4 nanoparticles and nitrogen‐doped GNRs (N‐GNRs) along with the porous structure impart the N‐GNR/Co3O4 hybrid with excellent ORR performance, which leads to a comparable onset‐potential to commercial Pt/C catalyst but larger current density, better long‐term stability and superior tolerance to crossover effects. [ABSTRACT FROM AUTHOR]

Published
2016
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47. In Situ Growth of Fe2O3 Nanoparticles on Highly Porous Graphene/Polyimide-Based Carbon Aerogel Nanocomposites for Effectively Selective Detection of Dopamine.

Author

Zhang, Youfang, Gao, Wei, Zuo, Lizeng, Zhang, Longsheng, Huang, Yunpeng, Lu, Hengyi, Fan, Wei, and Liu, Tianxi

Subjects
DOPAMINE, DIAGNOSIS of neurological disorders, NANOPARTICLES, POLYIMIDES, AEROGELS, NANOCOMPOSITE materials
Abstract

It is very important to develop a simple, efficient, and scaleable method for detection of dopamine (DA) with high sensitivity and selectivity to diagnose some serious neurological diseases. Herein, electro-catalysts for detection of DA are simply prepared based on Fe2O3 nanoparticles (NPs) decorated on highly porous carbon aerogels (CAs), which are derived from KOH activated graphene-polyimide aerogels. In the hierarchical nanocomposites (NCs), CAs provide large specific surface area, abundant mesopores, and macropores, and many sites for in situ growth of Fe2O3 NPs, thus effectively preventing the aggregation of Fe2O3 NPs. Moreover, CAs with 3D interconnected porous structures are able to shorten the charge transfer pathways through the intimate interaction between CAs and Fe2O3 NPs. Therefore, when applied as electro-catalysts for detection of DA, the optimized NC exhibits rapid amperometric response and a low detection limit of 0.109 × 10−6 m (S/N = 3), with a wide linear concentration range from 5 to 500 × 10−6 m. In addition, the oxidation peak of DA can be readily distinguished from the interference of uric acid and ascorbic acid. Therefore, the highly porous CAs derived from KOH activated graphene-polyimide aerogels are excellent substrates for in situ growth of Fe2O3 NPs, exhibiting high electrocatalytic activity for DA detection. [ABSTRACT FROM AUTHOR]

Published
2016
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50. Hierarchical ZnCo2O4@NiCo2O4 Core-Sheath Nanowires: Bifunctionality towards High-Performance Supercapacitors and the Oxygen-Reduction Reaction.

Author

Huang, Yunpeng, Miao, Yue ‐ E., Lu, Hengyi, and Liu, Tianxi

Subjects
ZINC compounds synthesis, OXIDATION-reduction reaction, SYNTHESIS of nanowires, FUEL cells, FUEL cell industry
Abstract

Increasing energy demands and worsening environmental issues have stimulated intense research on alternative energy storage and conversion systems including supercapacitors and fuel cells. Here, a rationally designed hierarchical structure of ZnCo2O4@NiCo2O4 core-sheath nanowires synthesized through facile electrospinning combined with a simple co-precipitation method is proposed. The obtained core-sheath nanostructures consisting of mesoporous ZnCo2O4 nanowires as the core and uniformly distributed ultrathin NiCo2O4 nanosheets as the sheath, exhibit excellent electrochemical activity as bifunctional materials for supercapacitor electrodes and oxygen reduction reaction (ORR) catalysts. Compared with the single component of either ZnCo2O4 nanowires or NiCo2O4 nanosheets, the hierarchical ZnCo2O4@NiCo2O4 core-sheath nanowires demonstrate higher specific capacitance of 1476 F g−1 (1 A g−1) and better rate capability of 942 F g−1 (20 A g−1), while maintaining 98.9 % capacity after 2000 cycles at 10 A g−1. Meanwhile, the ZnCo2O4@NiCo2O4 core-sheath nanowires reveal comparable catalytic activity but superior stability and methanol tolerance over Pt/C as ORR catalyst. The impressive performance may originate from the unique hierarchical core-sheath structures that greatly facilitate enhanced reactivity, and faster ion and electron transfer. [ABSTRACT FROM AUTHOR]

Published
2015
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