In Figure 3b the typical cycle of t

In Figure 3b the typical cycle of the Ag/AgCl and Na2Mn5O10
system is reported for the two separate electrodes (vs Ag/AgCl/
KCl 3.5 M reference electrode). In the presence of the dilute
electrolyte, the potential difference of the two electrodes is small.
In step 1 the battery is charged by removing the ions from AgCl
and Na2Mn5O10, thus gradually increasing the potential difference
of the two electrodes. The current density applied is
250 μA cm
2
, and a time limit of 20 min is imposed (see Supporting
Information). During step 2, the dilute solution is substituted
with the concentrated one, and consequently the potential
difference between the two electrodes increases significantly.
During step 3, the battery is discharged, and the ions are captured
by the electrodes, while the potential difference gradually decreases.
The applied current density is
250 μA cm
2
, with a time
limit of 20 min. The voltage difference between the Ag/AgCl and
Na2Mn5O10 electrodes is plotted during this cycling process (ΔE
vs q) in Figure 3c. After one full cycle, the energy density produced
is about 29 mJ cm
2 (power density 10.5 μW cm
2
).
The spikes in the potential difference observed at the beginning
and end of step 1 (A and A0
) and step 3 (B and B0
) are due to
electrochemical losses, known as overpotential. Due to this loss,
the practical gained potential is VG ≈ 0.100 V (74% efficiency, as
compared to the thermodynamically predicted potential gain). It
is possible to optimize the experimental configuration to improve
this gain as well, as the electrodes are currently at a distance of
approximately 1 cm from each other. The resistance of the
solution was 75 Ω for the diluted solution (75% of the total
internal resistance of the device) and 5 Ω in the concentrated one
(20% of the total internal resistance of the device), creating a high
overpotential. This overpotential could be greatly decreased (and
thus the power and/or energy efficiency significantly increased)
by designing a more optimized cell geometry using closer
electrode spacing and allowing a small amount of seawater to
remain in the cell when adding the river water to reduce the
resistance of the solution (see Supporting Information). Thus,
this system can be further optimized in order to increase the
energy recovery in each cycle. The experimental energy produced
with respect to cycle number is reported in Figure 3d. It is
important to note that the system operation was very stable for
100 cycles, with essentially no observable loss in energy production
over this period. This consistent power production is
expected, since both anionic and cationic electrodes are always
operating within the stability window of water, and the electrode
materials are very stable in the aqueous environment.
In order to probe possible complications which could exist in a
real system, we also conducted measurements with real water
samples collected from local natural water sources (see Supporting
Information). There was no decrease in cycling performance
when these samples were used, and we observed no electrode
degradation, self-discharge, or other detrimental phenomenon.
The energy conversion efficiency of this cell was 75%.
The extractable power from the difference of salinity of river
and seawater that could be obtained in many different countries
around the world is summarized in Figure 2c (data from ref 10).
If the energy from mixing entropy was harnessed from all these
rivers, the power obtained could reach up to 2 TW, which is
∼13% of the current total global energy requirement.11 This
energy can also be easily harvested at low temperatures, and is
completely renewable, since the ultimate source is the solar
energy which powers the water cycle.
Thus far, we have only considered the possibility of energy
production by harvesting the free energy dissipated by mixing
seawater and river water. However, this system could be modified
to operate on a smaller scale using solar energy to distill water,
with complete recycle of the electrolyte to achieve conversion of
solar energy into electrical energy. To further examine this
concept, we investigated electrolytes based on the reaction

Kết quả (Việt) 1:

In Figure 3b the typical cycle of the Ag/AgCl and Na2Mn5O10system is reported for the two separate electrodes (vs Ag/AgCl/KCl 3.5 M reference electrode). In the presence of the diluteelectrolyte, the potential difference of the two electrodes is small.In step 1 the battery is charged by removing the ions from AgCland Na2Mn5O10, thus gradually increasing the potential differenceof the two electrodes. The current density applied is250 μA cm
2, and a time limit of 20 min is imposed (see SupportingInformation). During step 2, the dilute solution is substitutedwith the concentrated one, and consequently the potentialdifference between the two electrodes increases significantly.During step 3, the battery is discharged, and the ions are capturedby the electrodes, while the potential difference gradually decreases.The applied current density is
250 μA cm
2, with a timelimit of 20 min. The voltage difference between the Ag/AgCl andNa2Mn5O10 electrodes is plotted during this cycling process (ΔEvs q) in Figure 3c. After one full cycle, the energy density producedis about 29 mJ cm
2 (power density 10.5 μW cm
2).The spikes in the potential difference observed at the beginningand end of step 1 (A and A0) and step 3 (B and B0) are due toelectrochemical losses, known as overpotential. Due to this loss,the practical gained potential is VG ≈ 0.100 V (74% efficiency, ascompared to the thermodynamically predicted potential gain). Itis possible to optimize the experimental configuration to improvethis gain as well, as the electrodes are currently at a distance ofapproximately 1 cm from each other. The resistance of thesolution was 75 Ω for the diluted solution (75% of the totalinternal resistance of the device) and 5 Ω in the concentrated one(20% of the total internal resistance of the device), creating a highoverpotential. This overpotential could be greatly decreased (andthus the power and/or energy efficiency significantly increased)by designing a more optimized cell geometry using closerelectrode spacing and allowing a small amount of seawater toremain in the cell when adding the river water to reduce theresistance of the solution (see Supporting Information). Thus,this system can be further optimized in order to increase theenergy recovery in each cycle. The experimental energy producedwith respect to cycle number is reported in Figure 3d. It isimportant to note that the system operation was very stable for100 cycles, with essentially no observable loss in energy productionover this period. This consistent power production isexpected, since both anionic and cationic electrodes are alwaysoperating within the stability window of water, and the electrodematerials are very stable in the aqueous environment.In order to probe possible complications which could exist in areal system, we also conducted measurements with real watermẫu thu thập từ các nguồn nước tự nhiên địa phương (xem hỗ trợThông tin). Có là không có giảm hiệu suất Chạy xe đạpKhi các mẫu được sử dụng, và chúng tôi quan sát thấy không có điện cựcsuy thoái, tự xả, hoặc hiện tượng bất lợi.Chuyển đổi năng lượng hiệu quả của tế bào này là 75%.Lực đẩy extractable từ sự khác biệt của các độ mặn của sôngvà nước biển có thể được lấy ở nhiều quốc gia khác nhautrên toàn thế giới tóm tắt trong hình 2 c (dữ liệu từ ref 10).Nếu năng lượng từ pha trộn dữ liệu ngẫu nhiên được khai thác từ tất cả cácsông, sức mạnh thu được có thể đạt đến 2 TW, mà là∼13% của tổng số năng lượng toàn cầu requirement.11 hiện tại đâynăng lượng có thể cũng có thể dễ dàng thu hoạch ở nhiệt độ thấp, và làhoàn toàn tái tạo, kể từ khi nguồn cuối cùng là các năng lượng mặt trờinăng lượng mà quyền hạn chu kỳ nước.Vậy, đến nay, chúng tôi đã chỉ xem xét khả năng lượngsản xuất bởi thu hoạch năng lượng miễn phí ăn chơi bằng cách trộnnước biển và sông nước. Tuy nhiên, Hệ thống này có thể được sửa đổiđể hoạt động trên một quy mô nhỏ hơn bằng cách sử dụng năng lượng mặt trời để distill nước,với đầy đủ thùng của chất điện phân để đạt được chuyển đổinăng lượng mặt trời thành năng lượng điện. Để tiếp tục kiểm tra nàykhái niệm, chúng tôi điều tra điện dựa trên phản ứng