Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.

1. Isolated Iridium Sites on Potassium-Doped Carbon-
nitride wrapped Tellurium Nanostructures for Enhanced
Glycerol Photooxidation
Pawan Kumar, Abdelrahman Askar, Jiu Wang, Soumyabrata Roy, Srinivasu
Kancharlapalli, Xiyang Wang, Varad Joshi, Hangtian Hu, Karthick Kannimuthu,
Dhwanil Trivedi, Praveen Bollini, Yimin A. Wu, Pulickel M. Ajayan, Michael
M. Adachi, Jinguang Hu, Md Golam Kibria
Advanced Functional Materials, 2024, https://doi.org/10.1002/adfm.2

2. Figure 1. a) Synthesis scheme of K doped and CN2-functionalized carbon nitride (KCN) b) Te NRs/NSs
wrapping with KCN c) Decoration of Ir single atoms on TeKCN to fabricate TeKCNIr.

3. Figure 2. HR-TEM images of TeKCNIr NRs a) at 100 nm scale bar showing dense Te-core or thin KCN shell. b) at 20 nm scale bar c,d) at 5 nm
scale bar showing the presence of dense core and sparse amorphous KCN shell. HR-TEM images of TeKCNIr nanosheets e) at 0.2 µm scale f) at
5 nm scale showing dominant Te single crystal lattice and amorphous KCN at the edge. Inset showing FFT of image and g) enlarged part of
image f showing overlapped iFFT and corresponding interplanar distance. h) SAED pattern of TeKCNIr showing periodic bright spots for
monocrystalline Te. EDX elemental mapping of i–n) TeKCNIr NRs for K, Te, N, C, O and o–t) TeKCNIr NSs HAADF, Te, O, N, K, and Te/K
composite.

4. Figure 3. a) DR-UV–vis spectra, b) synchrotron-based WAXS spectra, inset 2D WAXS map of TeCNIr c) PL spectra at an excitation wavelength
of 370 nm. Excitation-Emission Matrix Spectroscopy (EEMS) map of d) CN, e) KCN, f) Te and g) TeKCN showing C K, N K, K L, and Te L edges.
NEXAFS spectra of materials in h) C K-edge i) N K-edge j) Te L-edge region. Color: CN (black), KCN (violet), KCNIr (green), Te (yellow), TeKCN
(blue), TeKCNIr (red).

5. Figure 4. AC-HAADF-STEM images of TeKCNIr at a) 5 nm scale bar showing bright spots for IrSA sites b) Enlarged area of the image a
showing IrSA sites distributed in CN matrix. c) at 5 nm scale showing another region with uniform Ir single atom distribution. d) EELS ADF
image showing scanned area and EELS elemental mapping for Te, O, N, K, C, RGB composite of Te (red), C (green), K (blue), RGB composite of
Te (red), K (green), and N (blue). e) Ir L3-edge XANES spectra of Ir foil, CNIrSA, IrCl3, IrO2, TeKCNIrP and TeKCNIr. f) FT-EXAFS spectra and
fitting for Ir foil, IrO2, CNIr and TeKCNIr. WT EXAFS map of g) Ir foil h) IrO2 i) CNIr j) TeKCNIr.

6. Figure 5. a) TRPL spectra of CN and TeKCNIr b) Photocurrent density versus time (J-t) plot during the light on-off cycle c) Photocatalytic
H2 evolution in the presence/absence of TEOA using CN, CNIr, KCN, TeKCN, TeKCNIr after 24 h d) Photocatalytic glycerol conversion and e)
glyceraldehyde yield and f) glyceraldehyde selectivity as a function of time under AM1.5G irradiation using Te, TeKCN5, TeKCN10, TeKCN15,
CNIr, CN, and TeKCNIr.

7. Figure 6. Photocatalytic a) glycerol conversion b) glyceraldehyde yield and c) glyceraldehyde selectivity under AM1.5G irradiation and 365,
400, 450, 500, 550, 600, and 650 nm LEDs using TeKCNIr catalyst. d) glycerol conversion e) glyceraldehyde yield and f) glyceraldehyde
selectivity after 24 h in the presence of BQ, IPA and EDTA as O2
•−, •OH and h+ scavengers respectively (AM1.5G irradiation). EPR spectra of
reaction product using under dark and after 5, 10 min irradiation under AM1.5G irradiation using g) TEMPO as photogenerated hole trapping
agent and DMPO as h) superoxide radical i) hydroxyl radical spin labeling agent.

8. Figure 7. a) Band diagram of Te, KCN before and after contact showing the charge flow and plausible mechanism of
glycerol oxidation. b) optimized geometry of TeKCN, c) charge density difference iso-surface of TeKCN and d)
optimized structures of TeKCNIr.

9. Figure S1. Synthesis scheme for the (a) KCNIr and (b) CNIr (c) TeKCNIrP

10. Figure S2. Synthesis scheme of carbon nitride (CN) by thermal annealing of dicyandiamide.

11. Figure S3. (a) HR-TEM images of CN at 10 nm scale bar showing amorphous graphenic
sheets (b) SAED pattern with a large ring for amorphous structure.

12. Figure S4. HR-TEM images of KCN at (a) 200 nm scale bar showing graphenic sheets (b) at 20 nm scale showing largely amorphous sheet with some
crystalline domains, bottom right inset show 3.6 Å d-spacing calculated using line scan, inset show FFT of the entire image showing diffraction ring from
(002) plane (c) middle inset shows iFFT of the selected area in image b showing resolved d-spacing, Top right FFT of the selected area showing circular
lattice fringes, bottom right iFFT calculated reciprocal distance of 1/3.4 Å. (d) SAED pattern of image b showing circular diffraction ring for (002) plane of
CN. (e) composite of C, N and K and elemental mapping for (f) K (g) N (h) C (i) EDX spectra of KCN showing various elements.

13. Figure S5. (a) Bright-field TEM images of TeKCN NRs (b) Dark field TEM images of TeKCN NRs at 50 nm (c) TEM images of TeKCN NRs showing
Te/TeO2 (46 nm) core and KCN shell (5 nm). Inset at the top shows FFT with intense diffraction spots for a dense crystalline Te/TeO2 core Bottom inset
shows FFT with a broad diffraction ring for an amorphous KCN shell. (d) SAED pattern of image c showing broad diffraction ring for KCN and intense
spots for Te/TeO2. (e) HAADF-STEM electron image of scan area and elemental mapping for (f) Te (g) O (h) N (i) K (j) C (k) composite of K and Te (l)
Composite of N and Te (m) EDX elemental mapping showing peaks for various elements.

14. Figure S6. HR-TEM images of TeKCN NRs at (a) 20 nm scale bar dense Te/TeO2 core and KCN shell. (b) at 10 nm scale bar showing crystalline lattice
fringes in the central region and amorphous zone at the edge. Bottom inset shows a d-spacing of 2.5 Å related to monocrystalline Te, Middle inset shows an
intensity line scan intensity profile to show lattice spacing. The upper inset shows FFT demonstrating sharp sports for single crystalline Te (c) iFFT image of
image b showing resolved lattice planes, inset showing calculated d-spacing. (d) SAED pattern showing sharp diffraction spots for Te nanostructure (e)
HAADF-STEM electron image of TeKCN NRs and elemental mapping for (f) Te (g) O (h) C (i) N (j) K (k) composite of K and Te (l) N and Te (m) K and
Te (n) EDX spectra.

15. Figure S7. (a) HAADF-STEM electron image TeKCN NSs and elemental mapping for (b) O
(c) C (d) K (e) Te (f) N (g) composite of N and Te (h) K and Te (i) EDX spectra.

16. Figure S8. EELS spectra of TeKCNIr showing various elements edges.

17. Figure S9. HR-TEM images of KCNIr at (a) 0.5 μm scale showing graphenic structure (b) at 10 nm scale bar showing amorphous sheet with some domain with typical CN
(002) lattice fringes, inset shows FFT of image with faint bright spots originated from (002) plane reflection (c) Enlarged area of image b showing CN lattice fringe with 3.3
Å d-spacing. Bottom left inset shows FFT with 3.3 Å d-spacing. The middle and right inset shows iFFT and corresponding d-spacing of 3.3 Å. (d) HR-TEM image at 10 nm
scale bar showing partial amorphous sheets with (002) plane lattice fringes. (e) Enlarged area of image b showing CN lattice fringe with 3.3 Å d-spacing. Bottom left inset
shows FFT with 3.3 Å d-spacing. Middle and right inset shows iFFT and corresponding d-spacing of 3.3 Å. (f) SAED pattern of image d showing broad circular ring for
largely amorphous carbon nitride materials.

18. Figure S10. AC-HAADF STEM images of KCNIr at (a-b) 10 nm scale bar showing bright spots for IrSA decorated on KCN sheets (b)
enlarged area of image b showing Ir SA sites, Inset showing line scan intensity profile for Ir SA. (d) ADF electron image showing EELS
scan area EELS elemental map of KCN for (e) C (f) N (g) K (h) EELS spectra showing C K-edge, K L-edge and N K-edges

19. Figure S11. HR-TEM images of TeKCNIrP at (a-c) 100 nm scale bar showing TeO2 nanoparticles distributed on KCN sheets (b) 50 nm scale
showing spherical TeO2 NPs embedded in KCN (c) at 20 nm scale showing individual NPs (d) at 10 nm scale showing lattice fringes for TeO2
and amorphous KCN, Inset shows FFT of the image with amorphous ring for CN and intense dots for TeO2 (e) enlarged area of image d showing
lattice fringes for TeO2, inset displayed interplanar distance. (f) SAED pattern showing circular rings for KCN and polycrystalline TeO2.

20. Figure S12. AC-HAADF STEM images of TeKCNIrP at (a) 100 nm scale bar showing TeO2 NPs (b) at 10 nm scale bar showing a single
TeO2 NP (c) at 10 nm scale bar showing IrSA. Inset showing line intensity profile. (d) ADF electron image showing EELS scan area and
EELS scan for (e) C (f) N (g) K (h) Te (i) O (j) RGB composite of Te (red), N (green), K (blue) (k) EELS spectra showing faint IrM and SK
regions.

21. Figure S13. (a) FTIR spectra of Lower to upper panel: CN, KCN, KCNIr, TeKCN5, TeKCN10, TeKCNIr (b) Raman spectra of Lower to
the upper panel: KCN, pristine Te, TeKCN (c) XRD pattern Lower to upper panel: CN, KCN (d) XRD pattern of Lower to upper panel:
KCN, pristine Te, TeKCNIr Color code: CN (black), KCN (violet), KCNIr (green), TeKCN5 (sky blue), TeKCN10 (dark blue), TeKCNIr
(red), pristine Te (yellow).

22. Figure S14. Synchrotron-based wide angle X-ray scattering (WAXS) 2D detector images and
the derived 1D diffraction patterns (a-b) CN and (c-d) CNIr (e-f) TeKCN10.

23. Figure S15. (a) XPS survey scan and HR-XPS in (b) C1s (c) N1s (d) O1s region for CN.

24. Figure S16. XPS survey scan for (a) KCN (b) TeKCN (c) TeKCNIr (d) TeKCNIrP.

25. Figure S17. HR-XPS of KCN in (a) C1s (b) N1s (c) O1s (d) S2p regions.

26. Figure S18. HR-XPS of KCNIr in (a) Survey scan (b) C1s (c) N1s (d) O1s (e) Cl2p and (f) Ir
4f regions.

27. Figure S19. HR-XPS of TeKCN in (a) C1s (b) N1s (c) O1s (d) Te3d regions.

28. Figure S20. HR-XPS of TeKCNIr in (a) C1s (b) N1s (c) Cl2p (d) Te3d (e) O1s and (f) Ir4f
regions.

29. Figure S21. HR-XPS of TeKCNIrP in (a) C1s (b) N1s (c) O1s (d) Te3d (e) Cl2p and (f) Ir4f
regions.

30. Figure 22. EXAFS spectrum of TeKCNIrP.

31. Figure S23. Optimized DFT models of (a) Ir metal (b) IrO2 (c) CNIr (d) KCNIr (e) TeCNIr (f)
TeKCNIr show bond length between Ir-Ir, Ir-O and Ir-N.

32. Figure S24. EIS Nyquist plot of CN, KCN and TeKCNIr.

33. Figure S25. HPLC chromatogram of glycerol oxidation product after 0, 8 and 24h showing the
evolution of glyceraldehyde peak.

34. Figure S26. HPLC chromatogram of standard glycerol (1.61), glyceric acid (1.46 g/L),
dihydroxyacetone, DHA (0.87 g/L) and reaction product (2 g/L 10X dilution) demonstrating
glyceric acid as a main by-product of the reaction.

35. Figure S27. 1H NMR spectra of reaction product demonstrating the presence of aldehyde
protons of glyceraldehyde.

36. Figure S28. Digital photograph of the reactor used for the photocatalytic oxidation of glycerol
under pressurized O2 (8 bar).

37. Figure S29. Photocatalytic glycerol oxidation to glyceraldehyde over TeKCNIr catalyst and
under pressurized O2 (8 bar) showing glycerol conversion and yield.

38. Figure S30. (a) CO2-TPD and (b) pyridine TPD spectra of upper to lower panel: CN
(yellow), KCN (violet), TeKCN10 (blue) and TeKCNIr (red)

39. Figure S31. DTBP (2,6-di-tert-butylpyridine) TPD spectra of upper to lower panel: CN
(yellow), KCN (violet), TeKCN10 (blue) and TeKCNIr (red)

40. Figure S32. Active sites count for the CN, KCN, TeKCN10 and TeKCNIr calculated by area
integration of CO2, pyridine and DTBP-TPD peaks.

41. Figure S33. Tauc plot obtained using Kubelka-Munk function showing the band gap of
different materials.

42. Figure S34. Mott-Schottky plot for KCN (violet), Te (black), TeKCN (blue) and TeKCNIr
(red) showing flat band potential of the materials.

43. Figure S35. UPS work function spectra (a) CN (b) KCN (c) TeKCN (d) TeKCNIr

44. Figure S36. XPS valence band spectra (a) CN (b) KCN (c) TeKCN (d) TeKCNIr

45. Figure S37. Band structure of Te, CN and KCN estimated using Tauc plot, Mott-Schottky, UPS
and XPS VB spectra. *EVB vs NHE=(ϕ+EVB)-4.55; *ECB vs NHE=(ϕ+EVB- Ehv)-4.55.

46. Figure S38. Optimized geometries of (a) 2 x 2 x 1 supercell of CN and (b) 3 x 3 x 1 supercell
of Te (001) surface.

47. Figure S39. (a) Optimized geometries of Te-C3N4, and (b) charge density difference iso-
surface of Te-C3N4.

48. Figure S40. Plot of Fermi energy corrected vacuum potential against the distance along the
normal direction to surface.