Shallow trap state-enhanced photocatalytic hydrogen evolution over thermal-decomposed polymeric carbon nitride

2020 ◽  
Vol 56 (44) ◽  
pp. 5921-5924
Author(s):  
Jiawei Xue ◽  
Mamoru Fujitsuka ◽  
Tetsuro Majima
Keyword(s):  
Photocatalytic Activity ◽  
Hydrogen Evolution ◽  
Carbon Nitride ◽  
Functional Group ◽  
Electron Trap ◽  
Trap States ◽  
Shallow Trap ◽  
Trap State ◽  
Oxygen Functional Group ◽  
Polymeric Carbon

Oxygen functional group-introduced shallow electron trap states enhance the photocatalytic activity of the thermal-decomposed polymeric carbon nitride for hydrogen evolution.

scholarly journals Polymeric Carbon Nitride Coupled with a Molecular Thiomolybdate Catalyst: Exciton and Charge Dynamics in Light-Driven Hydrogen Evolution

2020 ◽  
Author(s):  
Ashwene Rajagopal ◽  
Elham Akbarzadeh ◽  
Chunyu Li ◽  
Dariusz Mitoraj ◽  
Igor Krivtsov ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Energy Demand ◽  
Soft Matter ◽  
Carbon Nitride ◽  
Molybdenum Sulfide ◽  
Open Circuit ◽  
Trap States ◽  
Time Resolved ◽  
Light Absorbers ◽  
Polymeric Carbon

Solar hydrogen evolution from water is a necessary step to overcome the challenges of rising energy demand and associated environmental concerns. Low-cost photocatalytic architectures based on polymeric light absorbers coupled to highly efficient molecular catalysts might represent an attractive platform to address this issue. However, to-date, our mechanistic knowledge of these systems is still largely underdeveloped. In this study, a molecular molybdenum sulfide hydrogen evolving catalyst, [Mo<sub>3</sub>S<sub>13</sub>]<sup>2–</sup>, is loaded onto polymeric carbon nitride (CN<i><sub>x</sub></i>) photoabsorber by impregnation. The resulting composite shows enhanced photocatalytic activity for hydrogen evolution compared to pristine CN<i><sub>x</sub></i> under monochromatic visible light (<i>l </i>= 420 nm) irradiation in the presence of sacrificial reducing agents. The light-driven dynamics of excitons and charges involved in hydrogen evolution catalysis were studied by a combination of spectroscopic (steady-state and time-resolved photoluminescence, femtosecond time-resolved transient absorption) and photoelectrochemical (open-circuit photopotential transients) methods. We demonstrate that the molecular molybdenum sulfide catalyst, at optimum loading (10 wt% nominal), improves the charge separation in the CN<i><sub>x</sub></i> absorber by facilitating the depopulation of emissive (band-edge) or non-emissive (shallow trap) states, followed by an effectively catalyzed transfer of electrons from the charge-separated state (deep trap) to protons in the solution. The results provide important insights into the complex interplay between polymeric light absorbers and molecular redox catalysts, indicating that the electron transfer to the catalyst occurs on relatively longer (nanosecond – seconds) time scale, as the catalyst had no impact on the ultrafast (sub-nanosecond) photoinduced kinetics in the CN<sub>x</sub>. These findings are of crucial importance for further development of soft-matter based architectures for solar fuels production.

scholarly journals Polymeric Carbon Nitride Coupled with a Molecular Thiomolybdate Catalyst: Exciton and Charge Dynamics in Light-Driven Hydrogen Evolution

2020 ◽  
Author(s):  
Ashwene Rajagopal ◽  
Elham Akbarzadeh ◽  
Chunyu Li ◽  
Dariusz Mitoraj ◽  
Igor Krivtsov ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Energy Demand ◽  
Soft Matter ◽  
Carbon Nitride ◽  
Molybdenum Sulfide ◽  
Open Circuit ◽  
Trap States ◽  
Time Resolved ◽  
Light Absorbers ◽  
Polymeric Carbon

Solar hydrogen evolution from water is a necessary step to overcome the challenges of rising energy demand and associated environmental concerns. Low-cost photocatalytic architectures based on polymeric light absorbers coupled to highly efficient molecular catalysts might represent an attractive platform to address this issue. However, to-date, our mechanistic knowledge of these systems is still largely underdeveloped. In this study, a molecular molybdenum sulfide hydrogen evolving catalyst, [Mo<sub>3</sub>S<sub>13</sub>]<sup>2–</sup>, is loaded onto polymeric carbon nitride (CN<i><sub>x</sub></i>) photoabsorber by impregnation. The resulting composite shows enhanced photocatalytic activity for hydrogen evolution compared to pristine CN<i><sub>x</sub></i> under monochromatic visible light (<i>l </i>= 420 nm) irradiation in the presence of sacrificial reducing agents. The light-driven dynamics of excitons and charges involved in hydrogen evolution catalysis were studied by a combination of spectroscopic (steady-state and time-resolved photoluminescence, femtosecond time-resolved transient absorption) and photoelectrochemical (open-circuit photopotential transients) methods. We demonstrate that the molecular molybdenum sulfide catalyst, at optimum loading (10 wt% nominal), improves the charge separation in the CN<i><sub>x</sub></i> absorber by facilitating the depopulation of emissive (band-edge) or non-emissive (shallow trap) states, followed by an effectively catalyzed transfer of electrons from the charge-separated state (deep trap) to protons in the solution. The results provide important insights into the complex interplay between polymeric light absorbers and molecular redox catalysts, indicating that the electron transfer to the catalyst occurs on relatively longer (nanosecond – seconds) time scale, as the catalyst had no impact on the ultrafast (sub-nanosecond) photoinduced kinetics in the CN<sub>x</sub>. These findings are of crucial importance for further development of soft-matter based architectures for solar fuels production.

scholarly journals Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

2021 ◽  
Author(s):  
Julia Kröger ◽  
Alberto Jiménez-Solano ◽  
Gökcen Savasci ◽  
Vincent Wing-hei Lau ◽  
Viola Duppel ◽  
...  
Keyword(s):  
Particle Size ◽  
Photocatalytic Activity ◽  
Hydrogen Evolution ◽  
Carbon Nitride ◽  
Colloidal Stability ◽  
Photophysical Properties ◽  
Trap States ◽  
Time Resolved ◽  
Transport Studies ◽  
Carbon Nitrides

The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time-resolved photoluminescence spectroscopy, charge transport studies, and quantum-chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re-agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co-catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as an enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI-type carbon nitrides that can likely be generalized to related photocatalytic systems.<br>

scholarly journals Polymeric Carbon Nitride Coupled with a Molecular Thiomolybdate Catalyst: Exciton and Charge Dynamics in Light-Driven Hydrogen Evolution

2020 ◽  
Author(s):  
Ashwene Rajagopal ◽  
Elham Akbarzadeh ◽  
Chunyu Li ◽  
Dariusz Mitoraj ◽  
Igor Krivtsov ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Energy Demand ◽  
Soft Matter ◽  
Carbon Nitride ◽  
Molybdenum Sulfide ◽  
Open Circuit ◽  
Trap States ◽  
Time Resolved ◽  
Light Absorbers ◽  
Polymeric Carbon

Solar hydrogen evolution from water is a necessary step to overcome the challenges of rising energy demand and associated environmental concerns. Low-cost photocatalytic architectures based on polymeric light absorbers coupled to highly efficient molecular catalysts might represent an attractive platform to address this issue. However, to-date, our mechanistic knowledge of these systems is still largely underdeveloped. In this study, a molecular molybdenum sulfide hydrogen evolving catalyst, [Mo<sub>3</sub>S<sub>13</sub>]<sup>2–</sup>, is loaded onto polymeric carbon nitride (CN<i><sub>x</sub></i>) photoabsorber by impregnation. The resulting composite shows enhanced photocatalytic activity for hydrogen evolution compared to pristine CN<i><sub>x</sub></i> under monochromatic visible light (<i>l </i>= 420 nm) irradiation in the presence of sacrificial reducing agents. The light-driven dynamics of excitons and charges involved in hydrogen evolution catalysis were studied by a combination of spectroscopic (steady-state and time-resolved photoluminescence, femtosecond time-resolved transient absorption) and photoelectrochemical (open-circuit photopotential transients) methods. We demonstrate that the molecular molybdenum sulfide catalyst, at optimum loading (10 wt% nominal), improves the charge separation in the CN<i><sub>x</sub></i> absorber by facilitating the depopulation of emissive (band-edge) or non-emissive (shallow trap) states, followed by an effectively catalyzed transfer of electrons from the charge-separated state (deep trap) to protons in the solution. The results provide important insights into the complex interplay between polymeric light absorbers and molecular redox catalysts, indicating that the electron transfer to the catalyst occurs on relatively longer (nanosecond – seconds) time scale, as the catalyst had no impact on the ultrafast (sub-nanosecond) photoinduced kinetics in the CN<sub>x</sub>. These findings are of crucial importance for further development of soft-matter based architectures for solar fuels production.

scholarly journals Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

2021 ◽  
Author(s):  
Julia Kröger ◽  
Alberto Jiménez-Solano ◽  
Gökcen Savasci ◽  
Vincent Wing-hei Lau ◽  
Viola Duppel ◽  
...  
Keyword(s):  
Particle Size ◽  
Photocatalytic Activity ◽  
Hydrogen Evolution ◽  
Carbon Nitride ◽  
Colloidal Stability ◽  
Photophysical Properties ◽  
Trap States ◽  
Time Resolved ◽  
Transport Studies ◽  
Carbon Nitrides

The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time-resolved photoluminescence spectroscopy, charge transport studies, and quantum-chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re-agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co-catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as an enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI-type carbon nitrides that can likely be generalized to related photocatalytic systems.<br>

Tuning of the Oxygen Species Linker on the Surface of Polymeric Carbon Nitride to Promote the Photocatalytic Hydrogen Evolution Performance

ChemSusChem ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3605-3613 ◽  
Author(s):  
Qin Lei ◽  
Rongzhi Chen ◽  
Yurong Zhao ◽  
Huanyu Chen ◽  
Xinxin Long ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Carbon Nitride ◽  
Oxygen Species ◽  
Photocatalytic Hydrogen Evolution ◽  
Polymeric Carbon

Cobalt ion redox and conductive polymers boosted the photocatalytic activity of the graphite carbon nitride–Co3O4 Z-scheme heterostructure

2021 ◽  
Vol 45 (1) ◽  
pp. 162-168
Author(s):  
Tao Li ◽  
Jiandong Cui ◽  
Yezhan Lin ◽  
Kecheng Liu ◽  
Rui Li ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Synergistic Effect ◽  
Hydrogen Evolution ◽  
Carbon Nitride ◽  
Conductive Polymers ◽  
Cobalt Ion ◽  
Photocatalytic Hydrogen Evolution ◽  
Conductive Polyaniline

The enhanced photocatalytic hydrogen evolution performance of g-C3N4–Co3O4 2D–1D Z-scheme heterojunctions was achieved through the synergistic effect of the cobalt ion redox, conductive polyaniline, and a Co3O4 nanobelt.

Sign in / Sign up

Export Citation Format

Share Document