PDF Publication Title:
Text from PDF Page: 006
ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-020-20287-w Fig. 3 Estimation of SOEEins for SFB built with SJ-GaAs photoanode and BTMAP redox couples. a I–V performance of the GaAs photoanode at 50% SOC under solar cell mode (red line) and RFB mode (blue lines) in 0.2 M BTMAP electrolytes with the flow rate of 60 mL min−1 measured under one Sun illumination. The blue lines from light to dark represent the Ecell at 1–99% SOC of the RFB. Note that photocurrent instead of photocurrent density is plotted here. b Potential match profile of the SFB’s SOEEins as a function of Ecell, (red curve) and the state of charge (SOC, blue curve). simulated (based on the optimal E0cell of 0.74 V vs. SHE in Fig. 1d) and shown in Fig. 3b. The SJ-GaAs SFB device can be effectively charged with a high SOEEins > 15% at a SOC range from 0 to 54% (the charged capacity of 1.30 Ah L−1 when the SFB was charged to 54%), corresponding to a cell potential range from 0.49 to 0.75 V (the yellow shaded area in Fig. 3b). Operation and characterization of integrated SFB device. In light of the comprehensive operating condition analysis of the SJ- GaAs SFB, we performed long term SFB cycling test with the optimized operating conditions (charging the SFB at SOC range from 0 to 54% to ensure the SOEEins > 15%). During the cycling test, the integrated SFB was charged under solar recharge mode with simulated one Sun solar illumination and a 1.35 h time limit to control the SOC utilization range (ca. 0-54%), followed by galvanostatic discharging under the RFB mode with a current of 11 mA and a cutoff potential of 0.3 V. We used a synchronized potentiostat with two separated channels to monitor the Ecell of the integrated SFB (the blue connection in Fig. 1c and the data are displayed as the blue curve in Fig. 4a) and the charging photo- current of the SJ-GaAs photoanode (the red connection in Fig. 1c and the data are displayed as the red curve in Fig. 4a) throughout the cycling test. During each charging cycle, the SJ-GaAs pho- toanode of the SFB showed an initial photocurrent density of ~25.9 mA cm−2, which gradually decreased with the increasing SOC as predicted in Fig. 3a, and yielded an average photocurrent density of 11 mA cm−2 (i.e., a current of 6.18 mA with the light- harvesting area of the SJ-GaAs photoanode of 0.53 cm2). This integrated SJ-GaAs SFB reached an impressive initial SOEE of 14.3%. Enabled by the robust BTMAP-Vi/BTMAP-Fc redox couples and the TiO2 protection layer on GaAs photoelec- trode, the integrated SFB device was continuously cycled for 150 cycles and showed fairly stable performance with average CE and VE of 98.6% and 96.2%, respectively (Fig. 4b). Over the 150 solar charging and discharging cycles (408h), the SOEE decreased slightly from the initial value by 5.6%, resulting in an average SOEE of 13.3%. This decay can be attributed to the increased RDC of the SFB (Supplementary Fig. 9a, b), due to the capacity fade (Supplementary Fig. 9c, d) and the surface corrosion of the SJ- GaAs photoanode over the operation period (Supplementary Fig. 3f). The XPS analysis of the SJ-GaAs photoanode surface after 150 charge/discharge cycles (Supplementary Fig. 10) revealed diminished Pt and Ti signals and newly emerged Ga and As signals, which suggested that the Ti/TiO2/Pt protection layer was significantly damaged or peeled off during the long operation period to expose the vulnerable GaAs substrate to the electrolyte. In addition to the high SOEE, the solar power conversion utilization ratio (SPUR), defined as the ratio between the SOEE of the SFB and the PCE of the solid-state solar cell, is another important figure of merit for SFBs. Due to the rational E0cell matching and operating condition optimization, this SJ-GaAs SFB achieved a SPUR of 58.4% (based on a PCE of 22.78% for the SJ-GaAs solar cell). However, there is still considerable room for further improvements. First, the LSV of the GaAs photoanode exhibits a significantly decreased FF (52.77%, Fig. 3a) in comparison with that of the solid-state GaAs solar cell (FF of 77.32%, Fig. 1b). This FF decrease is caused by insufficient charge transfer at the photoanode/electrolyte interface, which is a common issue for photoelectrodes with high photocurrent density (>20 mA cm-2), as discussed in previous reports14,49. In the optimization of electrolyte concentration and flow rate as we have demonstrated here (Supplementary Fig. 6), a noticeable enhancement of FF in LSV curves is mainly attributed to the improved kinetics under the faster flow rate and higher concentration. We expect the FF to be further improved by developing redox couples with faster kinetics and engineering of the photoelectrode/electrolyte interface to facilitate charge extraction14,48. Second, because the SOEE of the SFB is very sensitive to the LSV behavior of the photoelectrode, the decreased FF of the GaAs photoanode would significantly alter its voltage matching with the redox couples in SFBs. On the other hand, the SOC swings will not create as much voltage mismatch in higher voltage photoelectrodes such as tandem III–V cell, because of the relatively small voltage shift through the J–V curves. Accordingly, a higher Voc photoelectrode is more likely able to achieve a better match and better SPUR of the SFB. (see Supplementary Fig. 11 for complete details). 6 NATURE COMMUNICATIONS | (2021)12:156 | https://doi.org/10.1038/s41467-020-20287-w | www.nature.com/naturecommunicationsPDF Image | flow battery enabled single-junction GaAs photoelectrode
PDF Search Title:
flow battery enabled single-junction GaAs photoelectrodeOriginal File Name Searched:
s41467-020-20287-w.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Salt water flow battery technology with low cost and great energy density that can be used for power storage and thermal storage. Let us de-risk your production using our license. Our aqueous flow battery is less cost than Tesla Megapack and available faster. Redox flow battery. No membrane needed like with Vanadium, or Bromine. Salgenx flow battery
CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)