Template-Free Synthesis of Highly Porous Boron. Nitride: Insights into Pore Network Design and Impact

Transcription

1 Template-Free Synthesis of Highly Porous Boron Nitride: Insights into Pore Network Design and Impact on Gas Sorption Sofia Marchesini a, Catriona M. McGilvery b, Josh Bailey c and Camille Petit a, * a Barrer Centre, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK b Department of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, UK c Department of Chemical Engineering, University College London, Gower Street, London WC1E 6BT, UK * camille.petit@imperial.ac.uk; Phone: +44 (0) (Petit C.)

2 Methods The reconstructed 3D TEM tomography data set was imported into Avizo (FEI Visualization Group, France) as a.rec file. Image processing steps were taken to remove the noise in the data, thus allowing a more reliable subsequent segmentation. A 3D Median filter was applied with a neighbourhood setting of 26 and 3 iterations, followed by a standard 3D Gaussian filter with a kernel size of 5. Manual verification through all slices confirmed that no major loss of features was encountered using this filtering procedure. A manual threshold was then applied to identify seed voxels in the two phases, by first selecting the high grayscale values attributable to the BN material. Subsequently, the remaining unassigned voxels were selected and shrunk by 10 voxels in all directions, allowing for growth towards the true interface in the next step. A typical watershed segmentation procedure was then followed via a gradient mask and inundation process leading to all voxels being assigned as either pore or BN. To account for small numbers of inaccurately labelled pores, a simple threshold procedure was followed within the BN label field to re-label these voxels. No smoothing or simplification was applied on generating the 3D surfaces seen in Figures 2b and 2e. To demonstrate the distinct pore morphologies of each of the two samples, a sub-volume was extracted from each 3D dataset and a surface generated for the pore phase. These surfaces are shown in Figures 2c and 2f.

3 Table S1. Structural parameters derived from N 2 sorption isotherms at -196 C for the various BN samples. From the data, one can observe the tunability of the porosity of the materials based on the synthesis method. V tot (cm 3 /g) V micro (cm 3 /g) V meso (cm 3 /g) %mic Sample S BET (m 2 /g) BN-U % BN-B % BN-BU0.5: % BN-BU1: % BN-BU2: % BN-BU3: % BN-BU4: % BN-BU8: % BN-M % BN-MU0.25: % BN-MU0.5: % BN-MU1: % BN-pellet %

4 Figure S1. XRD patterns for all porous BN samples. All samples exhibit an amorphous character.

5 Figure S2. SEM images for all porous BN samples synthesised from single N precursors: a, BN-M0.5; b, BN-U5; c, BN-B2; melamine-based multiple N-precursors: d, BN-MU0.25:5; e, BN-MU0.5:5; f, BN-MU1:5; and urea-based multiple N-precursors: g, BN-BU0.5:5; h, BN- BU1:5; i, BN-BU2:5; j, BN-BU3:5; k, BN-BU4:5; l, BN-BU8:5. Scale bar in the figures are 800 nm.

6 Figure S3. TEM images for single N-precursor BN: a-c, BN-U5 and multiple N-precursor: d-f, BN-MU1:5. The particles in Figures a and d were used for the tomography reconstruction.

7 Figure S4 Pore size distributions for porous BN samples obtained from: a, biuret-based samples and b, melamine-based samples.

8 Figure S5. Thermogravimetric curves showing the decomposition pattern of: a, the different precursors used to synthesise porous BN, and b, the different mixtures of precursors used to synthesise BN-MU1:5 and BN-U5 (i.e. urea, melamine, boric acid and urea, boric acid). The tests were obtained under nitrogen gas flow.

9 Figure S6. FTIR spectra of porous BN samples shoing the typical B-N in-plane stretching band (1350 cm -1 ) and the B-N-B out-of-plane bending band (800 cm -1 ).

10 Figure S7. XPS core level spectra for a, B 1s; b, N 1s; and c, O 1s for a typical porous BN sample: BN-MU1:5. d, Bar plot representing the relative atomic percentages for B, N and O for all BN samples.

11 Figure S8. a, CO 2, CH 4 and N 2 sorption isotherms at 25 C for BN-MU1:5 powder at low pressure; b, high pressure CO 2 and N 2 isotherms at 10 C, 25 C, 40 C for the same sample, c, heat of adsorption and the adsorption entropy for CO 2 for the same sample.

12 Figure S9. Bar plots with CO 2, N 2 and CH 4 sorption capacity at 25 C and 1 bar for: a, biuret-based and b, melamine-based porous BN samples.