of a Seawater Battery

Here we present a solar-assisted rechargeable seawater battery that integrates TiO2 nanorod photoanode and a seawater battery into a single unit. Solar seawater battery, which is the integration of photoanode and seawater battery by benchmarking the rechargeable solar battery.

Introduction

• Importance of Energy Storage System (ESS)
• Seawater battery (SWB)
• Introduction of SWB
• Cell configuration and mechanism of SWB
• Cathode current collector of SWB
• Limitation of SWB
• Photoelectrode -------------------------------------------------------------------------------------------- d 15
• Photoanode
• Previous researches
• Electro-catalysts
• Solar rechargeable battery
• Research proposal

Cell configuration and mechanism of SWB Figure 6 shows the cell configuration of SWB. The role of the catalyst is to improve the kinetics of cathode reactions and properties. Among the components of the SWB, the cathode current collector serves as a reaction channel for the anode reaction as well as an electron transfer path.

By improving the pantograph in the cathode part, the voltage efficiency and cycle stability of the SWB can be improved. By using this heated carbon felt (HCF), the charge and discharge voltage profile of the SWB can be lower than that evaluated using pristine carbon felt. Due to the sluggish kinetics of the OER and ORR, the charging and discharging processes of the SWB are accompanied by a large overvoltage (Figure 7).

Therefore, the voltage profile of the seawater battery has a wide voltage gap, which means that the voltage efficiency is low. The electrons of the counter electrode will balance the holes in the photoanode and the electrons will charge the device. To overcome the voltage efficiency problem of SWB, we designed a hybrid-type solar seawater battery (SSB) that combines photoanode and SWB in one device with a comparative analysis of SRB (Figure 12).

We expect to increase the voltage efficiency of the SWB by reducing the charging voltage through this design.

Figure 2. Components of the cost of a Li-ion Battery [17]

Results and Discussion

Cell configuration of Solar seawater battery

Mechanism of Solar seawater battery

Design of SSB cell tester

Design of Photoanode

In this case, the loss through the recombination of electron-hole pairs can be reduced, which is especially important for semiconductors with short hole diffusion lengths (Figure 17). Fourth, fundamental optical and electronic properties can be engineered and modified through controlled alteration of the nanomaterial structure. For example, changing the size of semiconductor nanocrystals to increase light absorption can adjust the band gap of semiconductor nanocrystals in the solar spectrum.

Moreover, the separation of electrons and holes would be expressively improved nanostructures if their diameters correspond to the size of the depletion layer. Fifth, the growth of single crystal nanomaterials on various substrates can be allowed by the unique bottom-up synthetic strategy without the formation of dislocations due to lattice mismatch between growth substrate and semiconductor.[92].

Figure 18. The difference of the distance for photogenerated holes between the bulk film and nanostructure

Preparation process of the TiO 2 Nanorods photoanode

Characterization of the TiO 2 Nanorods photoanode

To investigate the light absorption property of TiO2 nanorods photoanode, we measured wavelength range from 200 nm to 800 nm using the ultraviolet-visible (UV-Vis) under illumination (Figure 21). So, we have again confirmed that the synthesized TiO2 nanorods photoanode is in the rutile phase. As you can see, the morphology of the nanorods, such as diameter, was uniform, but verticality of TiO2 nanorods was low.

It has been reported due to the presence of the seed layer (TiO2 . polymer Sol). Schematic of the 3-electrode setup with TiO2 nanorod photoanode working electrode, Ag/AgCl 3M NaCl reference electrode, and Pt wire counter electrode. This means that the TiO2 nanorod photoelectrode can generate photocurrent only when it receives solar energy.

Under chopped light illumination, we confirmed that the generation of photocurrent due to the presence of light changes rapidly. This result suggests that the activity and stability of the TiO2 nanorod photoanode is high (Figure 24).

Figure 22. Absorbance of TiO 2 nanorods photoanode by using UV-Vis

Performance of Solar seawater battery

This means that the voltage efficiency can be increased by a thermodynamically favorable method using a TiO2 nanorods photoanode. These results mean that the solar-seawater battery system is stable during the photo-charging process. Therefore, we investigated how much the charge voltage can be lowered by using the TiO2 Nanorods photoanode.

In order to confirm how much it is possible to lower the charging voltage, we compared the possibility of photo charging of TiO2 Nanorods photoanode and heated carbon felt. An existing heated carbon felt seawater battery was charged at ∼3.8 V and discharged at. Under illumination, photo-charging was performed at ~2.6 V with a photoanode, and the discharge voltage was ~2.8 V with a heated carbon felt in a seawater solar cell.

As mentioned before, galvanostatic cycling tests performed on solar-seawater batteries used two channels to decouple and independently cycle the OER and ORR electrodes. This indicates that the solar-seawater battery could achieve the stable solar charging of the seawater cell with increased voltage efficiency.

Figure 27. The I-V curves of TiO 2 nanorods photoanode with seawater coin-type cell under dark state, 1 sun condition and chopped condition

Experimental

Preparation of TiO2 nanorods on FTO

많은 분들의 도움으로 저는 학위를 취득한 2년 동안 행복하게 공부하고 많은 성장을 이룰 수 있었습니다. 먼저, 제가 정말 부족할 때 기회를 주시고, 독립적인 연구자가 될 수 있도록 지도해주신 지도교수 김영식 교수님께 깊은 감사의 말씀을 전하고 싶습니다. 지난 2년 동안 함께 고난과 역경을 함께 해주신 YK그룹 선후배 여러분께 진심으로 감사드립니다.

윽, 연구실을 떠나신 진협 사부님께 정말 감사드립니다. 물질적으로나 정신적으로 도움을 주신 알파고정선님께 진심으로 감사드립니다. 이렇게 좋은 분들과 함께 연구실에서 일할 수 있어서 정말 행운이고 행복했습니다.

마지막으로 사랑하는 가족들에게 감사 인사를 전하고 싶습니다. 바쁘고 멀리 떨어져 있어서 집에 자주 방문하지 못했는데, 이제 좀 더 가까이 살면서 받은 은혜에 보답할 수 있게 되었습니다.

Preparation of cathode current collector

Conclusion

By benchmarking the solar rechargeable battery, we designed the solar seawater battery (SSB), which integrates the TiO2 nanorod photoanode and the seawater battery (SWB) into one device to solve the low voltage efficiency problem of the SWB to solve. To practically implement the SSB system, we then designed the SSB tester optimized for the cell design and configuration. During the photocharging process of the SSB, the photogenerated holes are transferred from the valence band to the photoanode-seawater interface, thereby oxidizing seawater to O2.

Meanwhile, the photoexcited conduction band electrons are transferred to the anode through the external circuit, reducing Na ions to Na metal, and the generated photovoltage is used to offset the required charging voltage. By harnessing solar energy, the photo-assisted charging of SSB was ∼2.6 V, which is 34% lower than its discharge voltage of ∼2.8 V compared to that of SWB through a thermodynamically favorable method using photoanodes with TiO2 nanorods.

For the higher voltage efficiency of the SSB, it is important to improve the PEC performance of TiO2. Among the various candidates, photoanode materials with a smaller band gap than TiO2, such as WO3 and BiVO4, can be used to further increase the voltage efficiency.

지난 2년 동안 좋은 환경과 좋은 사람들 덕분에 울산에서 잊지 못할 추억을 남겼습니다. 석사과정 동안 교수님의 가르침을 잊지 않고 항상 발전하여 우수한 학생이 되도록 노력하겠습니다. 바쁜 일정에도 불구하고 논문을 검토해주시고 아낌없는 조언을 해주신 최윤석 교수님, 장지욱 교수님께도 깊은 감사의 말씀을 드립니다.

박사님께도 감사의 말씀을 전하고 싶습니다. 아무것도 모르는 나에게 관심을 가져주시고, 연구에 임하는 태도를 포함하여 많은 것을 생각하고 발전시킬 수 있도록 도와주신 황수민님께. 그리고 항상 학생들에게 유용한 서류를 알려주는 퇴사를 앞둔 용일이, 동시에 입학해서 많은 것을 가르쳐주는 영진이, 석사 준비에 많은 도움을 주고 학업을 마친 영재도 연구실의 막내 역할을 하며 연구실의 비타민 역할을 하는 수용 동기를 부여하는 역할을 합니다. . 박식한 우석이는 연구 외의 문제가 있을 때마다 큰 도움이 되었고, 회의론자를 싫어하는 동갑내기 친구 현우는 처음 연구에 합류했을 때부터, 또한 석사 학위를 성공적으로 마칠 수 있도록 외부 연구도 진행했습니다. 그리고 현재 미국에 있는 바이폴라팀의 전 리더였던 재희님과 졸업 전에도 자주 어울리고, 졸업 후에도 종종 찾아와 스트레스를 풀러 와주던 혜인이에게도 너무 감사드립니다. 석사 학위.

모두가 열심히 노력하고 있는 만큼 좋은 결과가 있을 것이라 믿어 의심치 않습니다. 저는 부모님 밑에서 잘 자랐고, 사회에서 꼭 필요한 사람이 되었습니다.