Equation y = a + b*x Adj. R-Square Value Standard Error Intercept E Slope

Transcription

1 Absorbance (a.u.) Equation y = a + b*x Adj. R-Square Value Standard Error Intercept E Slope Electron concentration (mmol/l) Supplementary Figure 1. Calibration curve for solution with different reduction degrees. The absorbance of reduced H 3 PMo 12 O 40 (PMo 12, 1.0 mmol/l) solution around 700 nm in the UV-Vis spectrum has a linear relationship with the number of obtained electrons.

2 Temperature ( C ) Temperature ( C ) Extinction coefficient (1/cm) a DI water 1 mmol/l 10 mmol/l Wavelength (nm) c 80 d DI water 10 mmol/l 100 mmol/l DI water Actual Rection solution Irradiation time (min) Irradiation Time (min) Supplementary Figure 2. Investigation of solar thermal energy transfer with starch-h 3 PMo 12 O 40 (PMo 12 ) reaction system. (a) Experimental extinction coefficients with different concentration of heteropoly blue. The extinction coefficient of phosphomolybdic blue solution in this study can be calculated from the transmitted spectrum according to the Lambert-Beer law: ln(t(λ))=-lk en, where T(λ) is spectral transmittance, L is the width of the quartz cuvette (1 cm in this experiment), and K en is the extinction coefficient, which is a measurement of how strongly a chemical species absorbs light of a given wavelength. (b) Schematic diagram for light-to-heat efficiency measurement (1-insulated foam system; 2-glass test tube; 3-thermocouple; 4- simulated sunlight source; 5-data collector). (c) Temperature versus irradiation time curve for heteropoly blue reaction solution and DI water (atmospheric temperature 22 C) under simulated sunlight irrdiation. (d) Temperature curve of actual reaction solution and DI water under actual sunlight irradiation (1:00 PM-2:40 PM, September 5 th, Atlanta, atmospheric temperature 26 C). After simulated sunlight irradiation for 1 hour, the temperature of heteropoly blue reaction solution was 12 C higher than DI water. Also, the temperature increased up to 84 C for the actual reaction solution under actual sunlight irradiation. Clearly, the heteropoly blue reaction system would increase sunlight absorption to heat the solution, enhancing the oxidization efficiency of the starch-pmo 12 reaction.

3 Electron transfer (mmol/ml) ph Absorbance (a.u.) 4 a , 1, 1.5, 2, 3, 5 h Wavelength (nm) b Heating time (hr) Discharge time (hr) 0.5 Supplementary Figure 3. Investigation of electron and proton transfer in starch-h 3 PMo 12 O 40 (PMo 12 ) reaction system at elevated temperature. (a) UV-vis spectrums of the starch-pmo 12 solution during the thermal degradation process (diluted to 1 mmol/l PMo 12 ). (b) Number of electrons transferred and ph change during the thermal degradation (curve 1) and discharge time (curve 2).

4 %T C-O C=O Mo-O b -Mo Native Starch Starch-PMo 12 complex P-O a Mo=O d Mo-O c -Mo cm -1 Supplementary Figure 4. FT-IR spectrum of native starch and starch-h 3 PMo 12 O 40 (PMo 12 ) complex after light irradiation. FT-IR spectrum of starch-pmo 12 complex demonstrate that polyoxometalate clusters have interacted with starch and the basic structure of polyoxometalate is still preserved in the complex. Meanwhile, the characteristic bands of starch also appear, verifying the presence of starch in the complex. It is worth noting that the wavenumber of the stretching band of the hydroxyl groups of starch increased from 3300 to 3400 cm -1 and the stretching vibration of C-O bond of starch located at 1002 cm -1 has a serious distortion after the formation of the complex, which proves that a strong hydrogen bond was formed between PMo 12 and starch 1. In addition, a strong increase of the carboxylate group band was observed around 1630 cm -1 υ(c=o) and 3300 cm -1 υ(-oh), compared to native starch. This indicates the direct oxidation of starch by PMo 12 in the starch-pmo 12 complex under light irradiation. The characteristic peaks of PMo 12 in the starch-pmo 12 complex are slightly shifted when compared to the spectrum of standard PMo 12 in literature 41 (shown in Supplementary Table 1).

5 Supplementary Figure 5. Molecular weight distributions of starches with different reaction periods measured by GPC: a1: after photochromic reaction before discharge; a2: after discharge; a3 after discharge in 2 nd repeated cycle; a4: after discharge in 3 rd repeated cycle; b1: 1 st repeated cycle with thermal degradation; b2: 2 nd repeated cycle with thermal degradation.

6 = a O -C-H -OH (H 2 O) -CH-OH Chemical Shift (ppm) b -CHO HOOC- -C-OH Chemical Shift (ppm) Supplementary Figure 6. 1 H NMR and 13 C NMR spectrum of final products in the degradation of starch. (a) 1 H NMR and (b) 13 C NMR spectrum. The typical signals of the new-formed aldehyde group could be observed at 8.5 ppm in 1 H NMR spectrum. The chemical shift of H-resonances of CH-ring protons are at 4 ppm 1,2. The intensive peak at 5 ppm is ascribed to the protons of hydroxyl and water 1,2. For the 13 C NMR spectrum, the carbonyl carbon signals were observed between c.a. 170 ( CHO) and c.a. 180 ( COOH) ppm, which directly demonstrate the oxidation of starch. In summary, the major products in solution are aldehydes and organic acids after the degradation and oxidation of starch.

7 Supplementary Figure 7. Schematic of emission gas collection experiment used for GC analysis.

8 PMo 12 Reduced PMo Chemical shift (p.p.m.) Supplementary Figure P NMR spectrum of reaction solution after several repeated irradiation and discharge cycles. The peak species at ppm and ppm can be ascribed to PMo 12 and reduced PMo 12 respectively 3, which indicates that the H 3 PMo 12 O 40 (PMo 12 ) was stable.

9 Voltage (V) Power density (mw/cm 2 ) PMo 12 PW 12 (fully reduced) PV 3 Mo 9 PW Current density (ma/cm 2 ) Supplementary Figure 9. Voltage current density and power current density plots with different polyoxometalates (POMs) used in this solar induced fuel cell (PMo 12 is H 3 [PMo 12 O 40 ], PW 12 is H 3 [PW 12 O 40 ], and PV 3 Mo 9 is H 6 [PV 3 Mo 9 O 40 ]). Fully reduced PW 12 was obtained by reduce reaction using ascorbic acid. Other reactions were conducted by mixing the POMs with starch under light irradiation and heating at 95 C, ph 0.7, with POMs concentration of 0.25 mol/l.

10 Faradic Efficiency (%) Light Heat Discharge Time (hr) Supplementary Figure 10. Faradic efficiency versus time curve for photochromic and thermal degradation processes.

11 Supplementary Table 1. Comparisons of characteristic peaks of H 3 PMo 12 O 40 (PMo 12 ) Peaks Standard PMo 12 in Ref. 41 (cm -1 ) Starch-PMo 12 complex (cm -1 ) υ(mo O c Mo) υ(mo O b Mo) υ(mo=o d ) υ(p O a ) where O a is the oxygen of the central tetrahedral, O b is the bridged oxygen of two octahedral sharing a corner, O c is the bridged oxygen sharing an edge, and O d is the terminal oxygen.

12 Supplementary Table 2. Major peak values of number-average molecular weight (M n ) of the starches from GPC (See Supplementary Figure 5) for different reaction times Sample M n (g/mol) a ; 5216 a ; 4611 a ; 5323; 2874 a4 6823; 2844 b1 9117; 4017 b2 5759; 2642

13 Supplementary Table 3. Analysis of the emission gas by GC. The gas was collected using the device shown in Supplementary Figure 7. Results Concentration (mol%) Oxygen Nitrogen Carbon monoxide Carbon dioxide 0.628

14 Supplementary Notes Supplementary Note 1. Faradic efficiency of discharge process in this hybrid fuel cell Faradic efficiency (ε F ) can be calculated with the following equation 4 : where Q Discharging is the experimental charge quantity calculated from the discharge current-time curve, and Q POM is the maximum possible charge quantity released by reduced H 3 PMo 12 O 40 (PMo 12 ), calculated by spectrophotometry. I is the electric current obtained during the discharging process; n is number of electrons obtained per Keggin unit of polyoxometalate (POM); c POM is the concentration of POM; V is the volume of electrolyte solution; and F is the Faraday constant. Electron transfer in the starch-pmo 12 system with photochromic or thermal degradation was previously investigated, as shown in Figure 2b curve-1 and Supplementary Figure 3b curve-1. Results show that the total amounts of electrons stored in reduced PMo 12 solution are mmol e - /ml and mmol e - /ml during photochromic and thermal degradation respectively, which is equal to 1.23 and 2.13 electrons per Keggin unit for photochromic and thermal degradation respectively. The electron transfer during discharge is shown in 2b curve-2 and Supplementary Figure 3b curve-2 for photo irradiated and thermal degraded reactions respectively. These results were calculated by integrating the electric current over time in a single cell at room temperature. Thus, Faradic efficiencies for the photo and thermal processes were calculated and are shown in Supplementary Figure 10. Final results are as high as 91% and 94% for photo and thermal degradation respectively. (1)

15 Supplementary References: 1 Zhang, S.-D. et al. Preparation and properties of starch oxalate half-ester with different degrees of substitution. J Polym Res 17, (2010). 2 De Graaf, R. A., Lammers, G., Janssen, L. P. B. M. & Beenackers, A. A. C. M. Quantitative Analysis of Chemically Modified Starches by 1 H-NMR Spectroscopy. Starch - Stärke 47, (1995). 3 shikawa, E. & Yamase, T. Photoreduction processes of alpha-dodecamolybdophosphate in aqueous solutions: Electrical conductivity, 31 P NMR, and crystallographic studies. Bull. Chem. Soc. Jpn. 73, (2000). 4 Chu, D. & Jiang, R. Effect of operating conditions on energy efficiency for a small passive direct methanol fuel cell. Electrochim. Acta 51, (2006).