Abstract:Hydration plays an important role in the diffusion and sieving of ions within nanochannels. However, it is hard to quantitatively analyze the contribution of hydration to the diffusion rates due to the complex hydrogen-bond and charge interactions between atoms. Here, we quantitatively investigated the interfacial diffusion rates of a single hydrated ion with different number of water molecules on graphene surface through molecular dynamics simulation. The simulation results show the ballistic diffusion mode b… Show more
“…DFT calculations revealed that Na + ·3H 2 O has the lowest diffusion barrier (Figure d) because of the symmetry mismatch between the structure of Na + ·3H 2 O and the tetragonal NaCl(001) substrate, thus allowing the existence of a number of metastable states in which water molecules around the Na + can rotate collectively with an exceptionally low barrier. The specific hydration-number effect on the interfacial transport of sodium ions also exists for other alkali metal ions (Li + , K + ) and even for those on graphene surface . These works establish the direct correlation between the microscopic structure and transport mechanism of hydrated ions and open up a new way to control the ion transport process in nanofluidic systems by interfacial symmetry engineering.…”
Section: Probing Interfacial Water and Ice With Submolecular
Resolutionmentioning
confidence: 59%
“…The specific hydration-number effect on the interfacial transport of sodium ions also exists for other alkali metal ions (Li + , K + ) and even for those on graphene surface. 87 These works establish the direct correlation between the microscopic structure and transport mechanism of hydrated ions and open up a new way to control the ion transport process in nanofluidic systems 88 by interfacial symmetry engineering.…”
Section: Structure and Interfacial Transport Of Ion Hydratesmentioning
Conspectus
Water–solid interfaces have attracted
extensive attention
because of their crucial roles in a wide range of chemical and physical
processes, such as ice nucleation and growth, dissolution, corrosion,
heterogeneous catalysis, and electrochemistry. To understand these
processes, enormous efforts have been made to obtain a molecular-level
understanding of the structure and dynamics of water on various solid
surfaces. By the use of scanning probe microscopy (SPM), many remarkable
structures of H-bonding networks have been directly visualized, significantly
advancing our understanding of the delicate competition between water–water
and water–solid interactions. Moreover, the detailed dynamics
of water molecules, such as diffusion, clustering, dissociation, and
intermolecular and intramolecular proton transfer, have been investigated
in a well-controlled manner by tip manipulation. However, resolving
the submolecular structure of surface water has remained a great challenge
for a long time because of the small size and light mass of protons.
Discerning the position of hydrogen in water is not only crucial for
the accurate determination of the structure of H-bonding networks
but also indispensable in probing the proton transfer dynamics and
the quantum nature of protons.
In this Account, we focus on
the recent advances in the H-sensitive
SPM technique and its applications in probing the structures, dynamics,
and nuclear quantum effects (NQEs) of surface water and ion hydrates
at the submolecular level. First, we introduce the development of
high-resolution scanning tunneling microscopy/spectroscopy (STM/S)
and qPlus-based atomic force microscopy (qPlus-AFM), which allow access
to the degrees of freedom of protons in both real and energy space.
qPlus-AFM even allows imaging of interfacial water in a weakly perturbative
manner by measuring the high-order electrostatic force between the
CO-terminated tip and the polar water molecule, which enables the
subtle difference of OH directionality to be discerned. Next we showcase
the applications of H-sensitive STM/AFM in addressing several key
issues related to water–solid interfaces. The surface wetting
behavior and the H-bonding structure of low-dimensional ice on various
hydrophilic and hydrophobic solid surfaces are characterized at the
atomic scale. Then we discuss the quantitative assessment of NQEs
of surface water, including proton tunneling and quantum delocalization.
Moreover, the weakly perturbative and H-sensitive SPM technique can
be also extended to investigations of water–ion interactions
on solid surfaces, revealing the effect of hydration structure on
the interfacial ion transport. Finally, we provide an outlook on the
further directions and challenges for SPM studies of water–solid
interfaces.
“…DFT calculations revealed that Na + ·3H 2 O has the lowest diffusion barrier (Figure d) because of the symmetry mismatch between the structure of Na + ·3H 2 O and the tetragonal NaCl(001) substrate, thus allowing the existence of a number of metastable states in which water molecules around the Na + can rotate collectively with an exceptionally low barrier. The specific hydration-number effect on the interfacial transport of sodium ions also exists for other alkali metal ions (Li + , K + ) and even for those on graphene surface . These works establish the direct correlation between the microscopic structure and transport mechanism of hydrated ions and open up a new way to control the ion transport process in nanofluidic systems by interfacial symmetry engineering.…”
Section: Probing Interfacial Water and Ice With Submolecular
Resolutionmentioning
confidence: 59%
“…The specific hydration-number effect on the interfacial transport of sodium ions also exists for other alkali metal ions (Li + , K + ) and even for those on graphene surface. 87 These works establish the direct correlation between the microscopic structure and transport mechanism of hydrated ions and open up a new way to control the ion transport process in nanofluidic systems 88 by interfacial symmetry engineering.…”
Section: Structure and Interfacial Transport Of Ion Hydratesmentioning
Conspectus
Water–solid interfaces have attracted
extensive attention
because of their crucial roles in a wide range of chemical and physical
processes, such as ice nucleation and growth, dissolution, corrosion,
heterogeneous catalysis, and electrochemistry. To understand these
processes, enormous efforts have been made to obtain a molecular-level
understanding of the structure and dynamics of water on various solid
surfaces. By the use of scanning probe microscopy (SPM), many remarkable
structures of H-bonding networks have been directly visualized, significantly
advancing our understanding of the delicate competition between water–water
and water–solid interactions. Moreover, the detailed dynamics
of water molecules, such as diffusion, clustering, dissociation, and
intermolecular and intramolecular proton transfer, have been investigated
in a well-controlled manner by tip manipulation. However, resolving
the submolecular structure of surface water has remained a great challenge
for a long time because of the small size and light mass of protons.
Discerning the position of hydrogen in water is not only crucial for
the accurate determination of the structure of H-bonding networks
but also indispensable in probing the proton transfer dynamics and
the quantum nature of protons.
In this Account, we focus on
the recent advances in the H-sensitive
SPM technique and its applications in probing the structures, dynamics,
and nuclear quantum effects (NQEs) of surface water and ion hydrates
at the submolecular level. First, we introduce the development of
high-resolution scanning tunneling microscopy/spectroscopy (STM/S)
and qPlus-based atomic force microscopy (qPlus-AFM), which allow access
to the degrees of freedom of protons in both real and energy space.
qPlus-AFM even allows imaging of interfacial water in a weakly perturbative
manner by measuring the high-order electrostatic force between the
CO-terminated tip and the polar water molecule, which enables the
subtle difference of OH directionality to be discerned. Next we showcase
the applications of H-sensitive STM/AFM in addressing several key
issues related to water–solid interfaces. The surface wetting
behavior and the H-bonding structure of low-dimensional ice on various
hydrophilic and hydrophobic solid surfaces are characterized at the
atomic scale. Then we discuss the quantitative assessment of NQEs
of surface water, including proton tunneling and quantum delocalization.
Moreover, the weakly perturbative and H-sensitive SPM technique can
be also extended to investigations of water–ion interactions
on solid surfaces, revealing the effect of hydration structure on
the interfacial ion transport. Finally, we provide an outlook on the
further directions and challenges for SPM studies of water–solid
interfaces.
“…And the hydrated Na + ion combined with more water molecules would possess the lower ion-hydration energy, attributed to the formation of stable configuration. Thus, the hydrated Na + ions tend to move from upper region to lower region dominated by ion-hydration energy 24 , 25 , inducing the formation of net ions flow and electric signal. Fig.…”
Environment-adaptive power generation can play an important role in next-generation energy conversion. Herein, we propose a moisture adsorption-desorption power generator (MADG) based on porous ionizable assembly, which spontaneously adsorbs moisture at high RH and desorbs moisture at low RH, thus leading to cyclic electric output. A MADG unit can generate a high voltage of ~0.5 V and a current of 100 μA at 100% relative humidity (RH), delivers an electric output (~0.5 V and ~50 μA) at 15 ± 5% RH, and offers a maximum output power density approaching to 120 mW m−2. Such MADG devices could conduct enough power to illuminate a road lamp in outdoor application and directly drive electrochemical process. This work affords a closed-loop pathway for versatile moisture-based energy conversion.
“…As shown in Figure b, during the water desorption process, a water content gradient is constructed, where the region exposed to the environment will have fewer water molecules. In this way, the Na + ions have fewer neighboring water molecules in the region with less water content, which is believed to possess a higher ion-hydration energy. , Conversely, the region with more water content would weaken the relative energy. Governed by the ion-hydration energy difference, the highly “energetic” hydrated ions are driven toward the side with the “inert” ions during the occurrence of water desorption, similar to that of the gradient in ionic concentration.…”
As an emerging candidate for a sustainable power supply,
moisture-electric
generators (MEGs) have attracted great attention in recent years.
Unlike the conventional hydroelectric system, MEGs propose to harvest
energy from ambient moisture, driven by either ion diffusion under
a concentration gradient or the interaction between a solid–liquid
interface governed by electrostatic theory. Two-dimensional (2D) nanomaterials,
in particular hydrophilic graphene oxide (GO), have been considered
as the most promising materials for high-performance MEGs owing to
their unique structure and properties. In line with the development
of 2D nanomaterials, the recent electrical output of a single MEG
has been greatly raised from tens to hundreds of millivolts, which
is capable of powering commercial electronics. Herein, we have reviewed
the recent progress of 2D nanomaterials in MEGs. The mechanism of
moisture-induced electricity generation and strategies for tailoring
2D nanomaterials to enhance the output performance of MEGs are discussed.
The potential application of MEGs is also discussed in two categories:
sensing and power supply. Finally, the existing challenges and the
perspective of MEGs are proposed for future study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
