Photobase effect for just-in-time delivery in photocatalytic hydrogen generation

Abstract

Carbon dots (CDs) are a promising nanomaterial for photocatalytic applications. However, the mechanism of the photocatalytic processes remains the subject of a debate due to the complex internal structure of the CDs, comprising crystalline and molecular units embedded in an amorphous matrix, rendering the analysis of the charge and energy transfer pathways between the constituent parts very challenging. Here we propose that the photobasic effect, that is the abstraction of a proton from water upon excitation by light, facilitates the photoexcited electron transfer to the proton. We show that the controlled inclusion in CDs of a model photobase, acridine, resembling the molecular moieties found in photocatalytically active CDs, strongly increases hydrogen generation. Ultrafast spectroscopy measurements reveal proton transfer within 30 ps of the excitation. This way, we use a model system to show that the photobasic effect may be contributing to the photocatalytic H2 generation of carbon nanomaterials and suggest that it may be tuned to achieve further improvements. The study demonstrates the critical role of the understanding the dynamics of the CDs in the design of next generation photocatalysts.

Simultaneous Hydrogen Generation and Exciplex Stimulated Emission in Photobasic Carbon Dots

“…The compositions of other functional moieties are summarized in Figure 2g and Table S1. As reported previously, the photobasic effect of acridine is related to the pyridinic N atom in the conjugated heterocyclic molecule, where the photoinduced protonation occurs [18] . The above result suggests the photobasic sites could be also formed in the prepared CD samples, offering the possibility of obtaining photobasic CDs.…”

Simultaneous Hydrogen Generation and Exciplex Stimulated Emission in Photobasic Carbon Dots

“…The compositions of other functional moieties are summarized in Figure 2g and Table S1. As reported previously, the photobasic effect of acridine is related to the pyridinic N atom in the conjugated heterocyclic molecule, where the photoinduced protonation occurs [18] . The above result suggests the photobasic sites could be also formed in the prepared CD samples, offering the possibility of obtaining photobasic CDs.…”

Pt Sub‐Nanoclusters on ZIF‐Derived Ultrafine Cd x Zn 1− x S Solid Solution: High‐Performance Photoreforming Lactic Acid to H 2 and Value‐Added Chemicals

“…As shown in Figure 4A, mass spectrometry analysis of the evolved gas showed a predominant D 2 signal, indicating that hydrogen primarily originates from the reduction of protons in water, with only a minor contribution from LA. The observed kinetic isotope effect (KIE), evidenced by a significantly lower H 2 evolution rate in D 2 O (Figure 4B and Supporting Information S1: Figure S22), further corroborated that water is the primary proton source for H 2 generation, as the KIE affects the rate but not the source [16,45,46]. For the oxidative pathway, as shown in Supporting Information S1: Figure S23, several routes for LA conversion are possible [12,41,47].…”

Perylenetetracarboxylic acid nanosheets with internal electric fields and anisotropic charge migration for photocatalytic hydrogen evolution

“…The rate of D 2 evolution can reach 33.95 mmol g −1 h −1 under the full spectrum (Fig. 6c ), indicating that the origin of H 2 is aqueous protons 82 . The presence of the H/D isotope effect decreases the photocatalytic HER 83 , but in principle, it does not harm our inferences about the source of H 2 in the reaction systems.…”

Simultaneous Hydrogen Generation and Exciplex Stimulated Emission in Photobasic Carbon Dots

“…The compositions of other functional moieties are summarized in Figure 2g and Table S1. As reported previously, the photobasic effect of acridine is related to the pyridinic N atom in the conjugated heterocyclic molecule, where the photoinduced protonation occurs [18] . The above result suggests the photobasic sites could be also formed in the prepared CD samples, offering the possibility of obtaining photobasic CDs.…”

Pt Sub‐Nanoclusters on ZIF‐Derived Ultrafine Cd x Zn 1− x S Solid Solution: High‐Performance Photoreforming Lactic Acid to H 2 and Value‐Added Chemicals

“…As shown in Figure 4A, mass spectrometry analysis of the evolved gas showed a predominant D 2 signal, indicating that hydrogen primarily originates from the reduction of protons in water, with only a minor contribution from LA. The observed kinetic isotope effect (KIE), evidenced by a significantly lower H 2 evolution rate in D 2 O (Figure 4B and Supporting Information S1: Figure S22), further corroborated that water is the primary proton source for H 2 generation, as the KIE affects the rate but not the source [16,45,46]. For the oxidative pathway, as shown in Supporting Information S1: Figure S23, several routes for LA conversion are possible [12,41,47].…”

Perylenetetracarboxylic acid nanosheets with internal electric fields and anisotropic charge migration for photocatalytic hydrogen evolution

“…The rate of D 2 evolution can reach 33.95 mmol g −1 h −1 under the full spectrum (Fig. 6c ), indicating that the origin of H 2 is aqueous protons 82 . The presence of the H/D isotope effect decreases the photocatalytic HER 83 , but in principle, it does not harm our inferences about the source of H 2 in the reaction systems.…”

Simultaneous Hydrogen Generation and Exciplex Stimulated Emission in Photobasic Carbon Dots

“…The compositions of other functional moieties are summarized in Figure 2g and Table S1. As reported previously, the photobasic effect of acridine is related to the pyridinic N atom in the conjugated heterocyclic molecule, where the photoinduced protonation occurs [18] . The above result suggests the photobasic sites could be also formed in the prepared CD samples, offering the possibility of obtaining photobasic CDs.…”

Pt Sub‐Nanoclusters on ZIF‐Derived Ultrafine Cd x Zn 1− x S Solid Solution: High‐Performance Photoreforming Lactic Acid to H 2 and Value‐Added Chemicals

“…As shown in Figure 4A, mass spectrometry analysis of the evolved gas showed a predominant D 2 signal, indicating that hydrogen primarily originates from the reduction of protons in water, with only a minor contribution from LA. The observed kinetic isotope effect (KIE), evidenced by a significantly lower H 2 evolution rate in D 2 O (Figure 4B and Supporting Information S1: Figure S22), further corroborated that water is the primary proton source for H 2 generation, as the KIE affects the rate but not the source [16,45,46]. For the oxidative pathway, as shown in Supporting Information S1: Figure S23, several routes for LA conversion are possible [12,41,47].…”

Perylenetetracarboxylic acid nanosheets with internal electric fields and anisotropic charge migration for photocatalytic hydrogen evolution

“…The rate of D 2 evolution can reach 33.95 mmol g −1 h −1 under the full spectrum (Fig. 6c ), indicating that the origin of H 2 is aqueous protons 82 . The presence of the H/D isotope effect decreases the photocatalytic HER 83 , but in principle, it does not harm our inferences about the source of H 2 in the reaction systems.…”