February 17th, 2021

International Collaboration in the Era of COVID‐19Kyushu University - UC San Diego Joint Webinar Series

SDGs THINK and ACT Together

Environmental Materials fromNatural Resources for SDGs
- Solar Light Driven Chemical Conversion -Department of Earth Resources
Engineering
Kyushu University
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Keiko Sasaki(PhD, Prof. Department Chair)

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About our department
Department of Earth Resources Engineering, Kyushu University
QS World Ranking 36th (Mineral & Mining Engineering)

EconomicGeology

Geothermics

Exploration
Geophysics

Resources
Production &Safety Engineering

Energy Resources
Engineering

Mineral Processing,
Recycling &Environmental Remediation

RockMechanics

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What are we?: Department of Earth Resources Engineering
Global Resources
Low grade ores
Refractory ores
Urban mines
Coal fly ash
Moon exploration
Reusable energy
Geothermal
Solar
Biomass
Oil recovery

Global Environments

Minerals
andMaterials

EnergyAcid water
Groundwater
Utilization of sea water

CO2 reduction
CO2 storage
GlobalCO2 conversion
Water remediation
WarmingGlobalEconomics

Water

WaterPollution

Solar light driven chemical conversion

4Antivirals

Minerals
andMaterials
CO2 alcohols

EnergyPhotocatalyst coating
against Corona virus

Environments
NOx NO3-Biomass components  alcohols

Photocatalytic selfcleaning

2H2O  O2 + 2H2
Degradation of dyes,pesticides andpharmaceutical wastes

Water

Cr(VI) reduction etc…

GlobalWarming
CO2reduction

Photocatalytic
antifouling coating

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Photocatalysis

Fujishima and Honda, Nature, 1972, 238, 37-38.

i) light absorption (optical)ii) charge separation and transport(physicochemical)iii) surface chemical reaction  Visible light driven(physical)
 Highly available Recyclability
 Contributing to carbon reduction
 Contributing to energy source production

6Montmorillonite ‐ 2:1 type clay‐Tetrahedral layer (Si)
Octahedral layer (Al)9.5 Å

2D materialHigh surface area
Chemically and physicallystableFe contents
Large charge density(1.15 meq/ g)

Large band gap

Too large!

5.35 eV

Clay minerals have been believed as good supports for main
photocatalysts in the composites.(i.e., TiO2‐pillared clay)
Ding et al. 1999, JCIS, 209, 193. Ooka et al., 1999, JMC, 11, 2943.

Chuaicham et al. 2020

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Modification: Heteroatom‐doping
Fe-doped Bi2WO6

Layered Double Hydroxide (LDHs)

substitution
Fe-doping on the Bi2WO6generates a new e- donor level,Fermi level, and O vacancy.

The Mn+-O-Fe3+ oxo-bridges canreduce or prevent the recombination ofe- and h+.

Hu et al. 2018, ChemCatChem, 10, 3040.

Meng, et al. 2019, Small, 15(41),1902551.

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Modification: Heterojunction

Su et al., Adv. Sustainable Syst. 2020, 4, 2000130

9Fabrication of ZnTi‐layered double hydroxides (LDH) /Fe‐doped montmorillonite (MT)Zn(NO3)2
TiCl4(Zn:Ti = 4:1)
urea④③②
10‐30wt% MT①③Reflux
at 130℃ for 12 hultrasonication
at RT, for 3 h③③①ZTL/MTx%④Suspended in Fe3+ZTL/Fe@MTx%②10

DFT prediction of DOS for Fe‐doped MT and ZnTi‐LDHFe‐doped MT

Originally 2wt% Fe in MT

Chuaicham, Dabo, Sasaki et al., Appl. Surf. Sci., 546, 2021,148835

ZnTi‐LDH

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Photocatalytic reduction of Cr(VI) at pH 3
HCrO4- + 7 H+ + 3 e- = Cr3+ + 4 H2O

C0 = 10 mg/L
Xe‐lamp(250‐1000 nm)

E: ethanol (hole scavenger)12

Diffused Reflectance UV‐VIS Spectroscopy (DRS)

Eg (eV)

Kubelka-Munk equationαhν = A(hν-Eg)n/2α, absorption coefficientν, light frequency
A, proportionality constantMT

2.56 and 3.72

ZTL

3.41

ZTL/MT20%

3.34

ZTL/Fe@MT20%

3.25

13OFFON(b) Photocurrent(a) Photoluminescence spectra

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TEM-EDX elemental mapping for spent ZTL/Fe@MT20%

HCrO4- + 7 H+ + 3 e- = Cr3+ + 4 H2O

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Z-scheme photocatalytic mechanism in Fe(III) doped MT
decorated with LDH

16Role of Fe(III) doped MT in the photocatalyst composites
Aspects(i) light absorption(optical)Advantages

 Increased by composite with MT compared withZnTi-LDH only
 Increased by Fe-doping compared with no Fedoping LDH/MT(ii) charge separation  Generated the mid-trap state of electron by Fe as
an impurity in MT.
and transport
 Enhanced by Z-scheme heterojunction for electron(physicochemical)
transfer and avoided the recombination of excitedelectron(iii) surface chemical
reaction (physical)

 Provided the large surface area
 Enhanced the contact frequency with the main
photocatalyst by 2D-2D materials(iv) others Stabilized Cr(III) on the remaining surfaces of MTafter photoreduction of Cr(VI)O42-

Clay is not only a support for main photocatalyst in the composites,and involved in photochemical reactions.

17• Chitiphon Chuaicham, Radheshyam R Pawar, Keiko Sasaki, Dye-sensitized photocatalyst of sepiolite fororganic dye degradation, Catalysts, 9 (2019) 235-255.
• Karthikeyan Sekar, Chitiphon Chuaicham, Radheshyam R. Pawar, Keiko Sasaki, Wei Li, Adam Lee, KarenWilson, Template free mild hydrothermal synthesis of core-shell Cu2O(Cu)@CuO visible light
photocatalysts for N-acetyl-para-aminophenol degradation, J. Mater. Chem. A, 7 (2019) 20767-20777.
• Sekar Karthikeyan, Kassam Ahmed, Amin Osatiashtiani, Adam F. Lee, Karen Wilson, Keiko Sasaki, BenCoulson, Will Swansborough-Aston, Richard E. Douthwaite, Wei Li, Pompon Dahlia-like Cu2O/rGO
nanostructures for visible light photocatalytic H2 production and 4-chlorophenol degradation, Chem Cat
Chem, 12 (2020) 1699– 1709.
• Chitiphon Chuaicham, Karthikeyen Sekar, Jun Tae Song, Tatsumi Ishihara, Bunsho Ohtani, Keiko Sasaki,Importance of ZnTiO3 phase in ZnTi mixed metal oxide photocatalyst derived from layered doublehydroxide, ACS Appl. Mater. Intrfaces, 12 (2020) 9169−9180.
• Chitiphon Chuaicham, Radheshyam R Pawar, Karthikeyen Sekar, Yihuang Xiong, Ismaila Dabo, BunshoOhtani, Keiko Sasaki, Energy-resolved distribution of electron traps for O/S-doped carbon nitrides byreversed double-beam photoacoustic spectroscopy and the photocatalytic reduction of Cr(VI), Chem.
Comm., 56 (2020) 3793– 3796.
• Chitiphon Chuaicham, Radheshyam R Pawar, Sekar Karthikeyen, Bunsho Ohtani, Keiko Sasaki, Fabricationand characterization of ternary sepiolite/g-C3N4/Pd composites for improvement of photocatalytic
degradation of ciprofloxacin under visible light irradiation, J. Colloid. Interface Sci., 577 (2020) 397-405.
• Sekar Karthikeyan; Chitiphon Chuaicham; Umamahesh Balijapalli; Wei Li; Adam Fraser Lee; Keiko Sasaki,
Surfactant- and template-free low-hydrothermal assembly of hierarchical to cubic nanostructured CuO/Cu2O
photocatalysts with uniformed sizes, Appl. Cat. B: Environ., in press.
• Chitiphon Chuaicham, Yihuang Xiong, Sekar Karthikeyan, Weinan Chen, Li Zhang, Bunsho Ohtani, Ismaila
Dabo, Keiko Sasaki, A promising Zn-Ti layered double hydroxide/Fe-bearing montmorillonite composite asan efficient photocatalyst for Cr(VI) reduction: Insight into the role of Fe impurity in montmorillonite, Appl.
Surf. Sci., 546 (2021) 148835.
• Sekar Karthikeyan; Kassam Ahmed; Yang Bai; Keiko Sasaki, Wei Li, Quantum dot bismuth
vanadate/reduced graphene oxide photocatalyst for hydrogen evolution and bisphenol A degradation, Appl.
Mater. Today, (2021) 100963.

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Solar light driven chemical conversion
MineralsandMaterials

Conversion of biomass to energy sources(alcohol, phenol etc) and chemicals (vanilin,etc)
CO2 reduction (to methanol)
Degradation of pharmaceuticaland pesticide compounds

GlobalWarming
Energy

Water

Water
Pollution