Supporting Information 3D Printing of Artificial leaf with Tunable Hierarchical Porosity for CO 2 Photoreduction Liao Chen, Xingwei Tang, Peiwen Xie, Jun Xu, Zhihan Chen, Zuocheng Cai, Peisheng He, Han Zhou*, Di Zhang, Tongxiang Fan* Figure S1. Image of the 3D printing apparatus. Figure S2. (a) Specific surface area of samples with different DBSA/TIA mass ratio. (b) Pore size distribution of the as-patterned structure after calcination. Figure S3. Photographs of inks with 15 nm and 30 nm SiO 2 nanospheres filler. Figure S4. Optical images of SiO 2 -DBSA-TIA patterns. Figure S5. (a) N 2 adsorption-desorption isotherms. (b) XPS spectrum of the as-obtained TiO 2 after KOH etching. Figure S6. X-ray diffraction data obtained after calcining the DBSA-TIA ink at 550 C. Figure S7. Thermogravimetric analysis of the DBSA-TIA ink. Figure S8. SEM-EDS data of the final TiO 2 patterns. Figure S9. Reaction setup for evaluation of CO 2 photoreduction activity. Table S1. Comparison with other TiO 2 -based CO 2 photoreduction systems for gas phase reaction Table S2. Basic parameters for the simulations on gas flow velocity and gas diffusion. 1
Figure S1. Image of the 3D printing apparatus. Figure S2. (a) Specific surface area of samples with different DBSA/TIA mass ratio. (b) Pore size distribution of the as-patterned structure after calcination (ink with 14.4 wt% DBSA/TIA mass ratio). 2
Figure S3. Photographs of inks with 15 nm (left) and 30 nm (right) SiO 2 nanospheres filler (3.2, 6.4, 9.6, 12.8 wt% SiO 2 /TIA mass ratio from left to right, 14.4 wt% DBSA/TIA mass ratio is constant). The original TIA precursor was light yellow. With solvent evaporation and gelation, concentrated inks formed and the color of the inks turned darker and orange. A printable SiO 2 -DBSA-TIA ink with low SiO 2 content was dark yellow. With the addition of SiO 2 nanospheres, inks became light yellow. Increasing SiO 2 nanospheres and decreasing Ti content resulted in the color change. Continous increasing SiO 2 /TIA mass ratio made inks color lighter and destroyed their printing behaviors simultaneously. Figure S4. Optical image of SiO 2 -DBSA-TIA patterns before calcination. 3
Figure S5. (a) N 2 adsorption-desorption isotherm curve of DBSA-TIA ink with 14.4 wt% DBSA/TIA mass ratio and SiO 2 -DBSA-TIA ink with 3.2 wt% SiO 2 /TIA mass ratio. (b) XPS spectrum of the as-obtained TiO 2 after KOH etching, SiO 2 /TIA mass ratio is 12.8wt%, with the inset of the Si spectrum. Figure S6. X-ray diffraction data obtained after calcining the DBSA-TIA ink with 14.4 wt% DBSA/TIA mass ratio at 550 C. 4
Figure S7. Thermogravimetric analysis of the DBSA-TIA ink. TGA results demonstrated that the precursors decomposed with increasing temperature. Complete organic decomposition occured by 500 C, which was in good agreement with the onset of crystallization. Due to the total mass loss observed, the as-patterned structures undergo significant volumetric shrinkage during calcination. Figure S8. SEM-EDS data of the final TiO 2 patterns (3.2 wt% SiO 2 /TIA mass ratio and 14.4 wt% DBSA/TIA mass ratio). 5
Figure S9. Reaction setup for CO 2 photoreduction activity measurement. 6
Table S1 Comparison with other TiO 2 -based CO 2 photoreduction systems for gas phase reaction Catalysts Reaction Conditions Product yield (µmol/g catalyst /h) TiO 2 UV irradiation (4 near-uv fluorescent CH 4 : 4.11, CO: black lamps,15 W); Reaction time: 2 h, 0.14,C 2 H 6 : 0.10 with CO 2 H 2 H 2 O in gas phase, 3.7mg TiO 2. TiO 2 pellets UV irradiation (200 W Hg/Xe-lamp); CH 4 : 5.6 Reaction time: 7.5 h, with CO 2 H 2 O in gas phase, 200µg catalyst. Ag-TiO 2 UV irradiation (four 8W UVA lamps, CH 4 : 2.64 average intensity: 3.25 mw cm 2 ); Reaction time: 8 h, with CO 2 H 2 O in gas phase. Pt-TiO 2 UV irradiation (300W Xe-lamp); CH 4 : 2.5 Reaction time: 4 h, with CO 2 H 2 O in gas phase, 100mg catalyst. N-doped TiO 2 CdS/TiO 2 Co-TiO 2 NaOH-TiO 2 (no metal cocatalyst) 3D-printed Au/RuO 2 TiO 2 visible light(λ>400nm, average intensity: 0.37 ± 0.05 mw cm 2 ), Reaction time: 6 h, with CO 2 H 2 O in gas phase, 250mg catalyst. visible light(λ>400nm) Reaction time: 8 h, with CO 2 H 2 O in gas phase, 0.18 ± 0.06 g catalyst. UV irradiation (125 W Hg lamp); Reaction time: 8 h, with CO 2 H 2 O in gas phase, 0.18 ± 0.06 g catalyst. Irradiate under visible light (300 W xenon arc lamp, λ>400nm), with CO 2 H 2 O in gas phase, 100mg catalyst 6 hours irradiation under a 300W Xe lamp, with H 2 O and CO 2 in gas phase, 80mg catalyst 24 hours irradiation with a 300W Xe lamp. Reaction with H 2 O and CO 2 in gas phase, 50mg catalyst CH 4 : 0.93 CH 4 : 0.11, CO: 1.37 CH 4 : 0.37, CO: 2.00 CH 4 : 0.09, CO: 1.94 CH 4 : 8.67, H 2 : 18.33 CH 4 : 0.29, CO: 0.21 Reference 1 2 3 4 5 6 7 8 This work 7
The following part is the detailed information for the gas diffusion behaviors simuations. Table S2. Basic parameters for the simulations on gas flow velocity and gas diffusion. Basic parameters Reactor volume Initial CO 2 concentration Initial CO concentration CO 2 flow velocity (u) CO 2 flux (Q) Frequency factor (A) Activation energy (E) Ratio constant (R g ) Reaction temperature (T) Reference pressure (p) Surface diffusivity (D) Volume force (F) Porosity(ε p ) permeability(κ) Value 9 mm 3 0 mol m -3 0 mol m -3 2.5 cm s -1 50mol m -2 s -1 10 6 m 3 s -1 mol -1 3 10 4 J mol -1 8.314 J mol -1 K -1 293.15 K 1 atm 1 10-6 m 2 s -1 0 0.3 1 10-9 m 2 In the porous bed, a reaction as shown in Equation S1 takes place with CO 2 as the input and CO and CH 4 as the output: hv AS( s) + CO CO+ CH Equation S1 2 4 The stationary Navier-Stokes equations describe the fluid flow in the free-flow regions. In the porous bed, the Brinkman equations are applied for porous medias. 9 A Fickian approach for mass diffusion and transport can be utilized, assuming that the modeled species are present in low concentrations compared to the solvent gas. The mass transport for the three species CO 2, CO, and CH 4 can therefore be modeled with the convection-diffusion equation (Equeation S2): u c i = V ( Di c i )+ R i 8 Equation S2
c i denotes the concentration (mol/m 3 ), D i is the diffusivity (m 2 /s), and R i is the reaction rate for species i (mol/(m 3 s)). Because the reaction takes place in the porous bed only, the reaction term is zero in the free-flow regions. The reaction is a second order irreversible reaction and the rates are given by 10 R CO2 = - k f c CO c CH4 R CO = k f c CO c CH4 R CH4 = k f c CO c CH4 Equation S3 where k f is the reaction rate constant, which in turn is temperature dependent according to the Arrhenius law: k f = A f exp[-e a /RT] Equation S4 Where A f is the frequency factor ((m 3 s)/mol), A f =1 10 6 (m 3 s)/mol, E a is the activation energy (J/mol), E a = 30 10 3 J/mol, R is the universal gas constant (J/(mol,K)), and T is the local temperature (K). A constant velocity profile is assumed at the inlet boundaries u = u in Equation S5 For the outlet, a pressure condition is applied. In the mass transport, the concentrations at the inlet are fixed c i = c i0,inlet Equation S6 At the outlet, the convection is assumed to dominate the mass transport according to Equation S7 n ( D i c i ) = 0 Equation S7 This implies that the gradient of ci in the direction perpendicular to the outlet boundary is negligible. This is a common assumption for tubular reactors with a high degree of transport by convection in the direction of the main reactor axis. The condition eliminates the need for specifying a concentration or a fixed value for the flux at the outlet boundary. At all other boundaries, insulating conditions were applied according to Equation S8. 11 n ( D i c i + c i u) = 0 Equation S8 9
References (1) Lo,C. C.; Hung, C. H.; Yuan, C. S.; Wu, J. F. Photoreduction of carbon dioxide with H 2, and H 2 O over TiO 2, and ZrO 2, in a circulated photocatalytic reactor. Sol. Energy Mater. Sol. Cells, 2014, 91, 1765-1774. (2) Tan, S. S.; Zou, L.; Hu, E. Kinetic modelling for photosynthesis of hydrogen and methane through catalytic reduction of carbon dioxide with water vapour. Catal. Today, 2008, 131, 125-129. (3) Kong, D.; Tan, J. Z. Y.; Yang, F.; Zeng, J. L.; Zhang, X. W. Electrodeposited Ag nanoparticles on TiO 2 nanorods for enhanced UV visible light photoreduction CO 2 to CH 4. Appl. Surf. Sci., 2013, 277, 105-110. (4) Mao, J.; Ye, L.; Li, K.; Zhang, X. H.; Liu, J. Y.; Peng, T. Y.; Zan, L. Pt-loading reverses the photocatalytic activity order of anatase TiO 2 {0 0 1} and {0 1 0} facets for photoreduction of CO 2 to CH 4. Appl. Catal., B 2014, 144, 855-862. (5) Phongamwong, T.; Chareonpanich, M.; Limtrakul, J. Role of chlorophyll in Spirulina, on photocatalytic activity of CO 2 reduction under visible light over modified N-doped TiO 2 photocatalysts. Appl. Catal., B 2015, 168, 114-124. (6) Beigi, A. A.; Fatemi, S.; Salehi, Z. Synthesis of nanocomposite CdS/TiO 2 and investigation of its photocatalytic activity for CO 2 reduction to CO and CH 4 under visible light irradiation. J. CO 2 Util. 2014, 7, 23-29. (7) Wang, T.; Meng, X. G.; Liu, G. G.; Chang, K.; Li, P.; Kang, Q.; Liu, L. Q.; Li, M.; Ouyang, S. X.; Ye, J. H. In situ synthesis of ordered mesoporous Co-doped TiO 2 and its enhanced photocatalytic activity and selectivity for the reduction of CO 2. J. Mater. Chem. A 2015, 3, 9491-9501. (8) Meng, X. G.; Ouyang S. X.; Kako, T.; Li, P.; Yu, Q.; Wang, T.; Ye, J. H. Photocatalytic CO 2 conversion over alkali modified TiO 2 without loading noble metal cocatalyst. Chem. Commun. 2014, 50, 11517-11519. (9) Alzahrani,F.; Aiouache, F. 3D Modelling of Flow Dynamics in Packed Beds of Low Aspect Ratio, Engineering Department, Lancaster University, Lancaster, UK. 2015. 10
(10) Varela, A. E.; García, J. C. Multiphysics Simulation of a Packed Bed Reactor, Excerpt from the Proceedings of the COMSOL Conference 2009 Boston. University of Carabobo, Valencia, Venezuela 2001. (11) Choi, S.; Drese, J. H.; Jones, C. W.; Adsorbent materials for carbon dioxide capture from large anthropogenic point sources, ChemSusChem 2009, 2, 796-854. 11