Hygroscopic salt-hydrogel
composite sorbents have attracted increasing
attention for atmospheric water harvesting (AWH) applications but
suffer from the salting-out effect. To this end, this work, for the
first time, discovers that the salting-in effect possessed by a zwitterionic
hydrogel is able to facilitate water vapor sorption by the hygroscopic
salt under otherwise the same conditions. For demonstration, zwitterionic
hydrogel of poly-[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium
hydroxide (PDMAPS) was synthesized, and the hygroscopic salt of LiCl
was embedded into PDMAPS to produce the salt-hydrogel composite. LiCl
salt not only endows the sorbent with high water vapor sorption capacity
but also facilitates the dissociation of self-association between
cationic and anionic groups of PDMAPS. This salting-in effect was
evaluated and confirmed experimentally and via density functional
theory (DFT) calculation. The salting-in effect renders the zwitterionic
hydrogel matrix with enhanced swelling capacity, leading to the sorbent’s
high AWH performance. With a photothermal component of CNT integrated
into the sorbent, a fully solar energy-driven AWH process was demonstrated
outdoors. This study provides important guidance to the design of
hydrogel-based AWH sorbents.
Metal- and halide-free, solid-state water vapor sorbents are highly desirable for water-sorption-based applications, because most of the solid sorbents are suffering from low water sorption capacity or toxic metals, while...
Water electrolysis at high current density (1000 mA cm−2 level) with excellent durability especially in neutral electrolyte is the pivotal issue for green hydrogen from experiment to industrialization. In addition to the high intrinsic activity determined by the electronic structure, electrocatalysts are also required to be capable of fast mass transfer (electrolyte recharge and bubble overflow) and high mechanical stability. Herein, the 2D CoOOH sheet-encapsulated Ni2P into tubular arrays electrocatalytic system was proposed and realized 1000 mA cm−2-level-current-density hydrogen evolution over 100 h in neutral water. In designed catalysts, 2D stack structure as an adaptive material can buffer the shock of electrolyte convection, hydrogen bubble rupture, and evolution through the release of stress, which insure the long cycle stability. Meanwhile, the rich porosity between stacked units contributed the good infiltration of electrolyte and slippage of hydrogen bubbles, guaranteeing electrolyte fast recharge and bubble evolution at the high-current catalysis. Beyond that, the electron structure modulation induced by interfacial charge transfer is also beneficial to enhance the intrinsic activity. Profoundly, the multiscale coordinated regulation will provide a guide to design high-efficiency industrial electrocatalysts.
Ultrathin transition metal dichalcogenides (TMDs) are of particular interest as low-cost alternatives to highly active electrocatalysts because of their high surface activation energy. However, their striking structural characteristics cause chemical instability and undergo oxidation easily. Establishing a transparent material model for unraveling oxidation-dependent electrocatalysis is of great importance for designing more efficient electrocatalysts. Herein, we fabricated an on-chip microcell that uses an individual nanosheet as the working electrode to evaluate the contribution of a single oxidation factor to hydrogen evolution reaction (HER) performance in the generation of oxidative molybdenum ditelluride (MoTe 2 ) for the fabrication of the on-chip electrocatalytic device. Moreover, O 2 plasma technology was utilized to control the degree of oxidation accurately by the processing time. Using oxidized MoTe 2 as a prototype demonstrated lower onset overpotential and activation energy of HER performance, which was optimized to some degree by oxidation. The incorporated oxygen during the oxidation process as an electron density modulator could manipulate the electron densities and contribute to the enriched surface charge and lower Gibbs reaction energy. Our present work provides atomic-level insights into the role of surface oxide in ultrathin TMDs HER catalysis by an on-chip electrocatalytic microdevice and the semiquantification of the model-structureperformance relationship, thus, opening the door for designing catalytic centers.
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