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SUPPLEMENTARY INFORMATIONARTICLE NUMBER: 16185 | DOI: 10.1038/NENERGY.2016.185

NATURE ENERGY | www.nature.com/natureenergy 1

[Supplementary Information]

Photocatalytic hydrogen generation from hydriodic acid using

methylammonium lead iodide in dynamic equilibrium with aqueous solution

Sunghak Park1†, Woo Je Chang 2†, Chan Woo Lee1, Sangbaek Park1, Hyo-Yong Ahn1, and Ki

Tae Nam1,2*

1Department of Materials Science and Engineering, Seoul National University, Seoul 151-744,

Korea

2Interdisciplinary Program for Bioengineering, Seoul National University, Seoul 151-742,

Korea

† These authors contributed equally to this work

* To whom correspondence should be addressed:

Ki Tae Nam, Ph.D.

Department of Materials Science and Engineering,

Seoul National University,

Seoul 151-744, Korea (Republic of)

Tel: 82-2-880-7094, Fax: 82-2-883-8197

E-mail: [email protected]

http://dx.doi.org/10.1038/nenergy.2016.185

http://www.nature.com/natureenergy



SUPPLEMENTARY INFORMATION

Supplementary Figure 1 | Scanning Electron Microscope (SEM) images of MAPbI3

prepared from organic solvent before (a) and after (b-d) dipping in a saturated solution.

The dipping times were 1 min (b), 10 min (c), and 30 min (d).





Supplementary Figure 2 | SEM images of the as-prepared MAPbI3 powder formed in

saturated HI solution. a, Image of MAPbI3 powders with wide size distributions. b, Magnified

image of one MAPbI3 powder.





Supplementary Figure 3 | X-ray diffraction (XRD) patterns of the precipitates with

various [I-] and [H+] concentrations. The black, red, blue, magenta, green, royal blue, purple,

and violet lines indicate –log[I-]=1, 0.5, 0, -0.2, -0.4, -0.5, -0.6 and -0.78. The black dashed line

indicates the peak position of the tetragonal MAPbI3 phase, the sky blue line indicates the peak

position of the monohydrate phase, the blue line indicates the peak position of the dihydrate

phase and the dark yellow line indicates the peak position of the PbI2 phase. The star indicates

the pattern of KI. a, The pH is -0.78. b, The pH is -0.6. c, The pH is -0.5. d, The pH is -0.4. e,

The pH is -0.2. f, The pH is 0. g, The pH is 0.5. h, The pH is 1.





Supplementary Figure 4 | Kubelka-Munk equation applied to the absorbance spectrum

of the MAPbI3 Powder. The energy is determined from the wavelength of the absorbance

spectrum. The optical absorption coefficient, F(α) = A2 / 2(1-A), is calculated where A is

absorbance, h is the planck constant (6.62607004×10-34 m2 kg s-1), and ν is the frequency of

light at a specific wavelength. The multiplying factor of P at (F(α)hν)P is confirmed as 2 due to

its linear drop line, which indicates the direct band gap character of the MAPbI3 powder. By

extrapolating the drop line to zero, the band gap can be determined to be 1.53 eV.





Supplementary Figure 5 | Photocatalytic HI splitting by the MAPbI3 powder in saturated

solution at various conditions. a, Photocatalytic HI splitting reaction of MAPbI3 powder in a

saturated solution under both light and dark conditions. b, Photocatalytic HI splitting reaction

of the saturated solution in the presence and absence of MAPbI3 powder.





Supplementary Figure 6 | Electrochemical H2 evolution from an MAPbI3 electrode in a

saturated solution system. a, Linear sweep voltammetry curve of an MAPbI3-loaded carbon

electrode in a saturated solution system. It shows significant electrocatalytic H2 evolution

activity. In contrast, an unmodified carbon electrode shows minimal H2 evolution activity in

aqueous HI. The carbon electrode also shows little H2 evolution activity in a saturated solution.

b, Theoretical amount of evolved H2 and measured amount of H2 after bulk electrolysis using

the MAPbI3 electrode. The bulk electrolysis was conducted at -0.9 V versus saturated calomel

electrode (vs. SCE), and the evolved H2 was analysed by GC.





Supplementary Figure 7 | Absorbance of the standard I3- solution for I3- quantification.

The standard solutions containing specific amounts of I3- were characterized by UV-Vis

absorption spectroscopy. The inset displays the absorbance curve of the standard at 353 nm.

The concentration of I3- in an unknown solution could be determined by substituting the value

of the absorbance at 353 nm into the I3- standard curve at 353 nm. The slope of the standard

curve was 0.0293, and intercept was 0.00299. The R2 value was 0.997.





Supplementary Figure 8 | Absorbance of 6.06 mol L-1 HI and the HI solution with added

H3PO2. Visible light could be absorbed by the 6.06 mol L-1 HI solution. In contrast, almost no

visible light could be absorbed by the H3PO2 added HI solution.





Supplementary Figure 9 | Linear sweep voltammetry measurement of H3PO2 aqueous

solution with different ions conditions. The applied anodic potential only oxidize I- ions into

I3- ions in the solution. Concomitant I3

- generation was visually observed by the formation of

dark brown colour at Pt working electrode during the sweep. H3PO2 remains stably in the

measured potential range.





Supplementary Figure 10 | XRD patterns of MAPbI3 powder before and after

photocatalytic HI splitting reaction. Tetragonal MAPbI3 phase was maintained after

photocatalytic HI splitting reaction





Supplementary Figure 11 | MAPbI3 powder cycling test. Each evacuation process was

performed with Ar after following 5 h of photocatalytic reaction. This cycling was repeated

three times.





Supplementary Figure 12 | Photocatalytic H2 evolution using various amounts of MAPbI3

powder. The rate of H2 evolution becomes sluggish at 1,000 mg of MAPbI3 due to the irregular

dispersion of the powder.





Supplementary Figure 13 | Photocatalytic H2 evolution of MAPbI3 powder with different

light irradiation areas at a light power of 100 mW cm-2.





Supplementary Figure 14 | XRD patterns of the MAPbI3 powder and thermally annealed

MAPbI3 powder in a polar solvent atmosphere. The intensities of the annealed MAPbI3

powder show higher values than the untreated MAPbI3 powder.





Material (Cocatalyst) Solar HI splitting efficiency (%) Experimental Condition

MAPbI3 (Pt)[This work] 0.81 % Photocatalyst 100 mW cm-2 (λ > 475nm)

MAPbI3[This work] 0.44 % Photocatalyst 100 mW cm-2 (λ > 475nm)

WSe2[This work] 2.9 × 10-4 % Photocatalyst

100 mW cm-2 (λ > 475nm)

Silicon (Pt)1 0.6% PEC cell 100 mW cm-2 (Full solar light)

WSe2 (Pt)2 4.2% PEC cell 100 mW cm-2 (Full solar light)

Si (PEDOT:PSS)3 3.7% PEC cell 100 mW cm-2 (Full solar light)

GaAs (Pt)4 2.6% PV-EC system 100 mW cm-2 (Full solar light)

Supplementary Table 1 | Solar HI splitting efficiency table. The MAPbI3 based

photocatalysis system shows an efficiency that is comparable to PEC and PV-EC type HI

splitting systems.





Supplementary Table 2 | Hydrogen evolution activity of the MAPbI3 photocatalyst with

various treatments under a light irradiation of 100 mW cm-2. The mol to mol comparison

was conducted based on the hydrogen evolved after 5 h as shown in Fig. 5a.

Material (Cocatalyst) Amount of hydrogen evolved for 1h from 1 mol of MAPbI3 (mmolH2 molMAPbI3-1h-1)

MAPbI3 (X) 6.94 Thermally annealed MAPbI3 in DMF

atmosphere (X) 13.3

Thermally annealed MAPbI3 in DMSO atmosphere (X) 22.7

Thermally annealed MAPbI3 in DMSO atmosphere (Pt) 33.4





Supplementary References

1 Ardo, S., Park, S.H., Warren, E.L. & Lewis, N.S. Unassisted solar-driven photoelectrosynthetic HI splitting using membrane-embedded Si microwire arrays. Energy Environ. Sci. 8, 1484-1492 (2015).

2 McKone, J.R., Potash, R.A., DiSalvo, F.J. & Abruña, H.D. Unassisted HI photoelectrolysis using n-WSe2 solar absorbers. Phys. Chem. Chem. Phys. 17, 13984-13991 (2015).

3 Mubeen, S., Lee, J., Singh, N., Moskovits, M. & McFarland, E.W. Stabilizing inorganic photoelectrodes for efficient solar-to-chemical energy conversion. Energy Environ. Sci. 6, 1633-1639 (2013).

4 Khaselev, O. & Turner, J.A. Photoelectrolysis of HBr and HI using a monolithic combined photoelectrochemical/photovoltaic device. Electrochem. Solid-State Lett. 2, 310-312 (1999).


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