You are currently viewing a new version of our website. To view the old version click .
MDPIMDPI
Search all articles
Physchem
Download PDF
  • Article
  • Open Access

5 November 2025

Efficient Photocathode of an Ultrathin Organic p-n Bilayer Comprising p-Type Zinc Phthalocyanine and n-Type Fullerene for Hydrogen Peroxide Production

,
and
Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki 036-8561, Japan
*
Author to whom correspondence should be addressed.
Physchem2025, 5(4), 49;https://doi.org/10.3390/physchem5040049
This article belongs to the Section Photophysics, Photochemistry and Photobiology
Version Notes
Order Reprints

Abstract

Hydrogen peroxide (H2O2) is a clean and environmentally friendly oxidant. At present, as an alternative to the conventional industrial procedure, namely, the anthraquinone method, a clean H2O2 production method is desired. The construction of an artificial photosynthetic system in which H2O2 can ideally be prepared from water and dioxygen (O2) is a promising approach. In such a system, an organic p-n bilayer comprising zinc phthalocyanine (ZnPc, p-type) and fullerene (C60, n-type) acts as a photocathode capable of O2 reduction to H2O2, where loading gold (Au) onto the C60 surface is necessary to achieve the corresponding reaction. However, the enhancement of the photocathodic activity of the organic p-n bilayer for H2O2 formation remains a critical issue. In this study, the effect of the thickness of an organo-bilayer (organo-photocathode) on photocathodic activity for H2O2 production was investigated. When both ZnPc and C60 were thin (approximately 10 nm each in thickness), the photocathodic activity of the ZnPc/C60 organo-photocathode was approximately 3.4 times greater than that of the thick ZnPc/C60 bilayer (i.e., ZnPc = ca. 70 nm and C60 = ca. 120 nm). The thin ZnPc/C60 bilayer exhibited a built-in potential at the p-n interface, where efficient charge separation occurs, resulting in a high concentration of electrons available for O2 reduction.

1. Introduction

Artificial photosynthesis reactions have been actively investigated to obtain fuels and chemicals such as molecular hydrogen [,,,,], hydrogen peroxide (H2O2) [,,,], and some products from carbon dioxide (CO2) [,,,]. H2O2 is a clean and environmentally friendly oxidizing agent, which is industrially produced using the anthraquinone method []. However, the industrial manufacturing method of H2O2 involves complex and multistep processes. In addition, significant energy consumption and organic waste emissions are major challenges limiting the commercialization of H2O2 []. Therefore, a clean and energy-saving H2O2 production method is urgently required to replace the conventional method.
H2O2 can be photocatalytically produced from water (H2O) and oxygen (O2) via the following redox reaction (Equation (1)):
H2O + 1/2 O2 ⟶ H2O2, ∆G° = +117 kJ·mol−1
Such an uphill reaction, which corresponds to artificial photosynthesis, can be expected to proceed via photocatalysis. Many studies on photocatalytic H2O2 production have been conducted [,,,,].
We have a track record of constructing an artificial photosynthesis system for water splitting featuring an organic p-n bilayer []. The water splitting system by Honda and Fujishima [], comprising titanium dioxide (TiO2) photoanode and Pt counter, is recognized to be a typical instance, but the overall splitting of water into O2 and H2 occurs only when a voltage bias is applied to the system. We reported the water splitting system composed of the TiO2 photoanode and organo-photocathode, where bias-free water splitting was found to occur (see Scheme S1). In the system featuring a TiO2 photoanode, our instance is an achievement that had not been discovered up to that time. In the Honda–Fujishima system, the oxidizing and reducing power generated at the TiO2 photoanode is available to the water splitting into O2 and H2, while our system can utilize oxidizing and reducing power separately photogenerated at TiO2 and organo-bilayer, respectively. In the latter, the electrons photogenerated at TiO2 do not move to Pt counter for H2 evolution (in the former), but to the holes remaining in the p-type layer of the organic p-n bilayer. Thus, it is summarized that, compared with the Honda–Fujishima system, the reason for bias-free water splitting in our system is kinetically favorable for the overall decomposition of water.
Based on this knowledge, we reported a photocatalytic system in which both a photocathode based on an organic p-n bilayer, comprising zinc phthalocyanine (ZnPc, p-type) and fullerene (C60, n-type), and a photoanode based on co-catalyst-loaded bismuth vanadate (BiVO4) were configured for H2O2 production (Scheme S1) []. In summary, the results of our previous study confirmed the production of H2O2 without the use of bias voltage in the photocatalytic system; however, the resulting efficiency was very low (i.e., <0.01% in maximum), and the rate-limiting step was the reduction of O2 to H2O2 at the photocathode in which the gold (Au)-co-catalyst was loaded at the C60 surface of the organo-bilayer (denoted as ZnPc/C60-Au). The activation of the ZnPc/C60-Au photocathode is a critical issue to improve our previous system.
In the present study, the photoelectrochemical reduction of O2 to H2O2 with ZnPc/C60-Au was investigated in terms of the thickness of the organo-bilayer employed (Scheme 1). In our previous study on H2O2 production [], the thickness of the ZnPc/C60 bilayer, which is recognized as optimal for reducing H+ to H2 [,,], was used without any modification (i.e., ZnPc = ca. 70 nm and C60 = ca. 120 nm). In this study, the validity of this approach was examined, along with the novel optimization of the organo-bilayer used as the photocathode.
Scheme 1. Illustration of H2O2 formation occurring at ZnPc/C60-Au photocathode.

2. Experimental

An indium tin oxide (ITO)-coated glass substrate (AGC Inc; sheet resistance: 8 Ω·cm−2; transmittance: >85%; ITO thickness: 174 nm) was used as the electrode substrate. ZnPc (TCI) was purified via sublimation before use (sublimation conditions: temperature, 530 °C; pressure, ~2 × 10−2 Pa) [,]. Pure C60 (>99.5%, TCI) was used as received. The other reagents used in this study were of extra-pure grade.
The ZnPc/C60 organo-bilayer was fabricated on an ITO-coated glass substrate via vapor deposition (ULVAC KIKO Inc., Saito, Miyazaki, Japan, pressure: <1.0 × 10−3 Pa; deposition speed: ~0.03 nm·s−1) [,]. ZnPc was first coated on the ITO substrate, after which C60 was placed on top of the ZnPc layer. Au was photoelectrochemically deposited onto the C60 surface of the organo-bilayer under potentiostatic conditions, where a single-compartment cell was composed of an organo-bilayer-modified working electrode (effective area: 1 cm2), a platinum counter electrode, and an Ag/AgCl (immersed in a saturated KCl solution; denoted as Ag/AgCl (sat.)) reference electrode in an acid solution (pH = 2) containing 5.0 × 10−4 mol·dm−3 HAuCl4·4H2O under an aerobic atmosphere. A potential of −0.2 V (vs. Ag/AgCl (sat.)) was applied to the modified ITO substrate for Au deposition. Photoelectrodeposition was performed using a potentiostat (HA-301, Hokuto Denko, Meguro-ku, Tokyo, Japan) equipped with a function generator (HB-104, Hokuto Denko, Meguro-ku, Tokyo, Japan), a Coulomb meter (HF-201, Hokuto Denko, Meguro-ku, Tokyo, Japan), and an X–Y recorder under illumination. The amount of Au deposited was controlled by monitoring the amount of charge that passed during photoelectrodeposition (i.e., 0.04 C). The aforementioned electrochemical setup was used to measure voltammograms and photocurrents to obtain an action spectrum under potentiostatic conditions, but using a phosphoric acid solution (pH = 2) as the electrolyte. The light intensity was measured using a power meter (type 3A, Ophir Japan, Saitama, Japan). A halogen lamp was utilized for irradiating the photocathode with a typical intensity of approximately 100 mW·cm−2. For the irradiation in the action spectrum measurements, the light source was combined with a monochromator (S-10, Soma Optics, Hinode, Tokyo, Japan) to generate monochromatic light. The electrolysis experiment for reducing O2 to H2O2 was conducted using a twin-compartment cell separated by a salt bridge (Scheme S2). The salt bridge preparation procedure is described elsewhere []. Calculation for the incident photon-to-current conversion efficiency (IPCE) and Faradaic efficiency (FE) are described in the Supplementary Materials (SM).
The crystal system of Au was analyzed by X-ray diffraction (XRD; SmartLab 9kW, Rigaku, Akishima, Tokyo, Japan). The surface of ZnPc/C60−Au was observed via scanning electron microscopy (SEM; JSM-7000F, JEOL, Akishima, Tokyo, Japan). The absorption spectra of the organo-bilayer, single layers, and the peroxo–titanium complex solution (vide infra) were measured using a spectrophotometer (Lambda 35, PerkinElmer, Shelton, CT, USA).
The thickness of the organic p-n bilayer was determined by visible-light spectroscopy. The absorption spectra of both ZnPc [] and C60 [] obtained were identical to those previously reported, and their absorption coefficients indicated the thickness of the films used (Table S1). Since the additivity of the absorption coefficient should be preserved in the visible-light absorption spectrum of the bilayer, the two unknown parameters for each thickness were estimated by solving simultaneous equations for the absorbance at two different wavelengths (see SM for the simultaneous equations). Such estimation procedures for the thickness of organic p-n bilayers are described in the literature [,].
Quantification of H2O2 was performed using the so-called titanium sulfate method []: a 30% titanium(IV) sulfate solution (0.5 mL) was added to the electrolyte solution (2.5 mL) at the reduction site (see Scheme S2); when H2O2 was present in the solution, a peroxo–titanium complex was formed from a Ti4+ ion and an H2O2 molecule according to the following equation (Equation (2)):
Ti4+ + H2O2 + 2H2O → H2TiO4 + 4H+
By measuring the absorption spectrum of the resulting solution, the amount of H2O2 formed was determined from the absorbance of the peroxo–titanium complex at 410 nm (molar absorption coefficient: 674 M−1·cm−1).

3. Results and Discussion

A typical X-ray diffraction pattern of Au particles is shown in Figure S1, in which Au is loaded on the C60 surface of the ZnPc/C60 organo-bilayer. The resulting pattern represents the formation of cubic Au, which is consistent with previous research []. The scanning electron microscopy image of the Au particles indicates the formation of fine Au particles in the order of <30 nm (Figure S2).
Voltammetric measurements were performed with regard to the thickness of the C60 and ZnPc layers. Figure 1a–c show the cyclic voltammograms (CVs) of the ZnPc/C60-Au photocathode under an O2 atmosphere, where the C60 layer thickness changed while the ZnPc layer thickness remained constant (i.e., ZnPc = ca. 70 nm). In the dark, almost no electrochemical response was confirmed. However, when ZnPc/C60-Au was irradiated, photocathodic currents were generated because of the reduction of O2; in addition, the photocurrents increased with thinning of the C60 layer. Furthermore, the ZnPc thickness was varied while keeping the thickness of the thin C60 layer (i.e., C60 = 6~7 nm) constant. Similarly to the change with the C60 thickness, the thinner the ZnPc layer, the more enhanced the photocurrent (Figure 1d,e). These voltammetric results demonstrate efficient photocurrent generation at ZnPc/C60-Au when thin ZnPc and C60 layers are used. By comparing the thinner layers (Figure 1e) with the thicker layers (Figure 1a), the photocurrent generated at −0.2 V (vs. Ag/AgCl (sat.)) was ca. 3~4 times higher with the former than with the latter. The photocathode shown in Figure 1e was subjected to repeated scans and demonstrated stable performance even after 10 scans (Figure 2).
Figure 1. Cyclic voltammograms of ZnPc/C60-Au under O2 atmosphere. Electrolyte solution: aqueous H3PO4 solution (pH = 2); scan rate: 20 mV/s; C60 film thickness in (a–c) (with constant ZnPc thickness of ca. 70 nm): (a) 123 nm, (b) 46 nm, (c) 13 nm; ZnPc film thickness in (d,e) (with constant C60 thickness of ca. 6~7 nm): (d) 115 nm, (e) 11 nm; light intensity: 100 mW/cm2; irradiation direction: from back of ITO-coated face.
Figure 2. CVs of ZnPc/C60-Au under O2 atmosphere with repeated scans. Electrolyte solution: aqueous H3PO4 solution (pH = 2); scan rate: 20 mV/s; film thickness of ZnPc/C60 bilayer: 10 nm for ZnPc and 4 nm for C60; light intensity: 100 mW/cm2; irradiation direction: from the back of the ITO-coated face.
Using thin organo-bilayer that showed the most efficient characteristics, some types of ZnPc/C60-Au were prepared by changing the amount of charge passed during Au deposition. Those CVs for the reduction of O2 are shown in Figure 3. It can be considered that the amount of Au deposited corresponds to the charge amount (see SM). CV characteristics were improved with increasing the deposited amount of Au; however, when the Au amount was too large, the CV characteristics deteriorated. Thus, the conditions of Figure 1e and Figure 2, where the thin organo-bilayers and constant amount of charge during Au deposition (i.e., 0.04 C) were employed, were confirmed to be optimum.
Figure 3. CVs of ZnPc/C60-Au for O2 reduction with changing the amount of charge passed during Au deposition ((a), 0.02 C; (b), 0.04 C; (c), 0.05 C). Electrolyte solution: aqueous H3PO4 solution (pH = 2); scan rate: 20 mV/s; film thickness of ZnPc/C60 bilayer: 11 nm for ZnPc and 6 nm for C60; light intensity: 100 mW/cm2; irradiation direction: from the back of the ITO-coated face.
To analyze the results of Figure 3, SEM images were observed with three types of Au loaded on the organo-bilayer (Figure S3). Comparing Figure S3a with Figure S3b, the particle size appears to increase with increasing charge amount. Figure S3c displays that the number of particles increase while maintaining the particle size with Figure S3b. In Figure 3, the surface concentration of electrons reaching the C60 surface should be constant because organo-bilayers of constant thickness were employed. As the number of Au particles increases, the number of active sites increases; however, the electron concentration per unit particle of Au decreases, and consequently, the activity of Au catalyst is diminished. Thus, it reveals that the deposition conditions of Figure S3b are optimum in the number and size of Au particles, efficiently highlighting the catalytic activity of Au.
Electrolysis for H2O2 production from O2 was investigated with some types of organo-photocathodes. The typical data are summarized in Table 1. Supporting the voltammetric results, the amount of H2O2 produced increased with decreasing thickness of the organo-bilayer. The FE value for the formation of H2O2 was always >90% (see SM for the FE calculation), where the H2O2 amount in entry 3 was ca. 3.4 times larger than that in entry 1.
Table 1. Electrolysis data for H2O2 production by ZnPc/C60-Au under illumination a.
Action spectrum measurements were performed for the photocurrents generated at ZnPc/C60-Au (Figure 4). Even when a thin ZnPc/C60 bilayer was used as photocathode, photocurrents were generated across the entire visible-light region. By comparing the resulting action spectrum with the single-layer ZnPc and C60 absorption spectra, the photocurrents originated from the absorption of both ZnPc and C60: in other words, the photocurrent generation around at 460–490 nm, where the absorption of ZnPc is almost absent, can be induced by the sole absorption of C60; photocurrents generated at wavelengths of >530 nm may have originated from ZnPc absorption.
Figure 4. Action spectrum of ZnPc/C60-Au photocurrents obtained under O2 atmosphere. The inset shows the typical absorption spectra of single-layer ZnPc and C60. Film thickness of ZnPc/C60 bilayer: 12 nm for ZnPc and 3 nm for C60; applied potential: −0.1 V vs. Ag/AgCl; light intensity: 0.1 mW/cm2; electrolyte solution: aqueous H3PO4 solution (pH = 2).
To gain insight into the thinner ZnPc/C60 organo-bilayer, rest potential was measured using single layers of ZnPc and C60. The results are presented in Table 2. By comparing the rest potential values of n-type C60 and p-type ZnPc, the latter exhibited a more positive potential than the former; furthermore, the magnitude of the potential difference between the ZnPc and C60 layers was independent of their thicknesses (i.e., ca. 0.5 V). These results demonstrate that built-in potential can be formed at the p-n interface even with a thin organo-bilayer, supporting the finding that series of photophysical events occur similar to photovoltaic cells of organic p-n bilayers []. Therefore, the photoelectrochemical reduction of O2 to H2O2 at ZnPc/C60-Au can be explained as follows. First, visible-light absorption occurs in both the ZnPc and C60 layers, and consequently, excitons are formed within both bilayers. The excitons attain at the p-n interface through excitation energy transfer, followed by the charge separation of excitons into electrons and holes at the hetero-interface. The photogenerated electrons move to the Au-coated C60 surface, thus resulting in the generation of reducing power for O2 reduction. The reducing power induced the reduction of H+ to H2, as previously reported by our group []. The potential of O2/H2O2 (+0.38 V vs. Ag/AgCl, at pH = 2) is more positive than that of H+/H2 (−0.32 V vs., Ag/AgCl, at pH = 2); thus, the O2 reduction occurring at the ZnPc/C60 bilayer is thermodynamically reasonable. The kinetics of O2 reduction should be proportional to the surface concentration of O2 and the number of electrons available for H2O2 formation on the Au co-catalyst. Considering that the O2 concentration was saturated under these experimental conditions, the photocathodic activity of ZnPc/C60-Au for producing H2O2 can be associated with the concentration of electrons on the Au co–catalyst. When employing the thin bilayer as a photocathode, the transport distance of electrons from the p-n interface to Au can be shortened, thus effectively enhancing the electron concentration at Au. This may also relate to the reduced carrier recombination between electrons and holes.
Table 2. Rest potential measured using single-layer ZnPc and C60 a.

4. Conclusions

This study investigated the effect of the thickness of a ZnPc/C60 bilayer for the development of efficient photocathodes capable of H2O2 formation from O2. The results demonstrate that a thin ZnPc/C60 bilayer acts as a superior photocathode when Au loaded on the C60 surface is employed as a co-catalyst. The thin bilayer reduced O2 to H2O2 by approximately 3.4 times more than the thick bilayer used in our previous study. This result can be attributed to the high concentration of electrons available for H2O2 formation on the Au co-catalyst, which is achieved through a series of efficient photophysical processes that occur within the thin bilayer.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/physchem5040049/s1. Scheme S1: Illustration of an artificial photosynthetic system for H2O2 formation; Scheme S2: Illustration of the electrolysis system used in this study; Determination of film thickness; Table S1: Absorption coefficients of ZnPc and C60; Calculation for the incident photon-to-current conversion efficiency (IPCE) and Faradaic efficiency (FE); Figure S1: XRD pattern of Au deposited on C60 surface of ZnPc/C60 organo-bilayer; Figure S2: SEM images of C60 surface of ZnPc/C60 organo-bilayer with (a) and without (b) Au loading. Figure S3: SEM images of Au particles by changing the amount of charge passed during Au deposition (the amount of charge during Au deposition: (a), 0.02 C; (b), 0.04 C; (c), 0.06 C).

Author Contributions

Conceptualization, T.A.; validation, T.A.; investigation, Y.S. and K.I.; resources, T.A.; writing—original draft, T.A.; supervision, T.A.; project administration, T.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by JSPS KAKENHI Grant Number JP22K05183 (T.A.).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

All data are available in the main text or the Supplementary Materials.

Acknowledgments

T. Abe acknowledges financial support from JSPS.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Qi, Y.; Zhang, B.; Zhang, G.; Zheng, Z.; Xie, T.; Chen, S.; Ma, G.; Li, C.; Domen, K.; Zhang, F. Efficient overall water splitting of a suspended photocatalyst boosted by metal-support interaction. Joule 2024, 8, 193–203. [Google Scholar] [CrossRef]
  2. Lin, L.; Ma, Y.; Vequizo, J.J.M.; Nakabayashi, M.; Gu, C.; Tao, X.; Yoshida, H.; Pihosh, Y.; Nishina, Y.; Yamakata, A.; et al. Efficient and stable visible-light-driven Z-scheme overall water splitting using an oxysulfide H2 evolution photocatalyst. Nat. Commun. 2024, 15, 397. [Google Scholar] [CrossRef]
  3. Xin, X.; Li, Y.; Zhang, Y.; Wang, Y.; Chi, X.; Wei, Y.; Diao, C.; Su, J.; Wang, R.; Guo, P.; et al. Large electronegativity differences between adjacent atomic sites activate and stabilize ZnIn2S4 for efficient photocatalytic overall water splitting. Nat. Commun. 2024, 15, 337. [Google Scholar] [CrossRef]
  4. Fu, H.; Zhang, Q.; Liu, Y.; Zheng, Z.; Cheng, H.; Huang, B.; Wang, P. Photocatalytic Overall Water Splitting with a Solar-to-Hydrogen Conversion Efficiency Exceeding 2% through Halide Perovskite. Angew. Chem. Int. Ed. 2024, 63, e202411016. [Google Scholar] [CrossRef]
  5. Takata, T.; Liu, L.; Hisatomi, T.; Domen, K. Best Practices for Assessing Performance of Photocatalytic Water Splitting Systems. Adv. Mater. 2024, 36, 2406848. [Google Scholar] [CrossRef]
  6. Kondo, Y.; Mizutani, S.; Kuwahara, Y.; Mori, K.; Sekino, T.; Yamashita, H. Perfluoroalkyl-functionalization of zirconium-based metal–organic framework nanosheets for photosynthesis of hydrogen peroxide from dioxygen and water. J. Mater. Chem. A 2025, 13, 3701–3710. [Google Scholar] [CrossRef]
  7. Xu, X.; Sui, Y.; Chen, W.; Huang, W.; Li, X.; Li, Y.; Liu, D.; Gao, S.; Wu, W.; Pan, C.; et al. The photocatalytic H2O2 production by metal-free photocatalysts under visible-light irradiation. Appl. Catal. B 2024, 341, 123271. [Google Scholar] [CrossRef]
  8. Liu, T.; Pan, Z.; Vequizo, J.J.M.; Kato, K.; Wu, B.; Yamakata, A.; Katayama, K.; Chen, B.; Chu, C.; Domen, K. Overall photosynthesis of H2O2 by an inorganic semiconductor. Nat. Commun. 2022, 13, 1034. [Google Scholar] [CrossRef] [PubMed]
  9. Kofuji, Y.; Isobe, Y.; Shiraishi, Y.; Sakamoto, H.; Tanaka, S.; Ichikawa, S.; Hirai, T. Carbon Nitride–Aromatic Diimide–Graphene Nanohybrids: Metal-Free Photocatalysts for Solar-to-Hydrogen Peroxide Energy Conversion with 0.2% Efficiency. J. Am. Chem. Soc. 2016, 138, 10019–10025. [Google Scholar] [CrossRef] [PubMed]
  10. Wang, W.; Zhang, W.; Deng, C.; Sheng, H.; Zhao, J. Accelerated Photocatalytic Carbon Dioxide Reduction and Water Oxidation under Spatial Synergy. Angew. Chem. Int. Ed. 2024, 63, e202317969. [Google Scholar] [CrossRef]
  11. Wang, L.; Qiu, C.; Chen, R.; Chen, X.; Ding, J.; Zhang, J.; Wan, H.; Guan, G. Constructing the facet junction on solid solution BiOBr1-xClx for efficient photocatalytic CO2 reduction with H2O. J. Alloys Compd. 2024, 985, 174022. [Google Scholar] [CrossRef]
  12. Nakamoto, T.; Iguchi, S.; Naniwa, S.; Tanaka, T.; Teramura, K. Surface Modifications of Heterogeneous Photocatalysts for Photocatalytic Conversion of CO2 by H2O as the Electron Donor. ChemCatChem 2024, 16, e202400594. [Google Scholar] [CrossRef]
  13. Cao, F.; Zhang, X.; Niu, X.; Lin, X.; Wu, T.; Zhong, S.; Lin, H.; Zhao, L.; Bai, S. Upgrading Single S-Scheme Heterojunction to Multi-S-Scheme Ones for Better Synergy of Photocatalytic CO2 Reduction and H2O Oxidation: The Third Component Location Matters. ACS Catal. 2024, 14, 12529–12540. [Google Scholar] [CrossRef]
  14. Riedl, H.J.; Pfleiderer, G. Preparation from Organic Compounds by the Alkyl-Anthraquinone Process. U.S. Patent Application No. C01B15/023, US2158525A, 16 May 1939. [Google Scholar]
  15. Ciriminna, R.; Albanese, L.; Meneguzzo, F.; Pagliaro, M. Hydrogen Peroxide: A Key Chemical for Today’s Sustainable Development. ChemSusChem 2016, 9, 3374–3381. [Google Scholar] [CrossRef] [PubMed]
  16. Chen, H.-Y.; Huang, J.-R.; Liu, J.-C.; Huang, N.-Y.; Chen, X.-M.; Liao, P.-Q. Integration of Plasmonic Ag(I) Clusters and Fe(II) Porphyrinates into Metal–Organic Frameworks for Efficient Photocatalytic CO2 Reduction Coupling with Photosynthesis of Pure H2O2. Angew. Chem. Int. Ed. 2024, 63, e202412553. [Google Scholar] [CrossRef] [PubMed]
  17. Abe, T.; Fukui, K.; Kawai, Y.; Nagai, K.; Kato, H. A water splitting system using organo-photocathode and titanium dioxide photoanode capable of bias-free H2 and O2 evolution. Chem. Commun. 2016, 52, 7735–7737. [Google Scholar] [CrossRef]
  18. Fujishima, A.; Honda, K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature 1972, 238, 37–38. [Google Scholar] [CrossRef]
  19. Ikezoi, K.; Chisaka, M.; Abe, T. Photocatalytic and photoelectrochemical production of hydrogen peroxide under acidic conditions in organic p-n bilayer/bismuth vanadate system. Int. J. Electrochem. Sci. 2022, 17, 221143. [Google Scholar] [CrossRef]
  20. Abe, T.; Chiba, J.; Ishidoya, M.; Nagai, K. Organophotocatalysis System of p/n Bilayers for Wide Visible Light-Induced Molecular Hydrogen Evolution. RSC Adv. 2012, 2, 7992–7996. [Google Scholar] [CrossRef]
  21. Abe, T.; Hiyama, Y.; Fukui, K.; Sahashi, K.; Nagai, K. Efficient p-zinc phthalocyanine/n-fullerene organic bilayer electrode for molecular hydrogen evolution induced by the full visible-light energy. Int. J. Hydrogen Energy 2015, 40, 9165–9170. [Google Scholar] [CrossRef]
  22. Abe, T.; Miyakushi, S.; Nagai, K.; Norimatsu, T. Study of the factors affecting the photoelectrode characteristics of a perylene/phthalocyanine bilayer working in the water phase. Phys. Chem. Chem. Phys. 2008, 10, 1562–1568. [Google Scholar] [CrossRef]
  23. Morikawa, T.; Adachi, C.; Tsutsui, T.; Saito, S. Multilayer-Type Organic Solar Cells Using Phthalocyanines and Perylene Derivatives. Nippon Kagaku Kaishi 1990, 1990, 962–967. [Google Scholar] [CrossRef]
  24. Capobianchi, A.; Tucci, M. Ruthenium phthalocyanine thin films for photovoltaic applications. Thin Solid Films 2004, 451, 33–36. [Google Scholar] [CrossRef]
  25. Abe, T.; Nakamura, K.; Ichinohe, H.; Nagai, K. Evaluation of photoanodic output on carbon cluster/phthalocyanine films with respect to the types of n-type conductors employed. J. Mater. Sci. 2012, 47, 1071–1076. [Google Scholar] [CrossRef]
  26. Eisenberg, G.M. Colorimetric Determination of Hydrogen Peroxide. Ind. Eng. Chem. Anal. Ed. 1943, 15, 327–328. [Google Scholar] [CrossRef]
  27. Swason, H.E.; Tatge, E. Standard X-ray diffraction powder patterns. Natl. Bur. Stand. Circ. 1953, 539, 33. [Google Scholar]
  28. Tanaka, S.; Hanada, T.; Ono, K.; Watanabe, K.; Yoshino, K.; Hiromitsu, I. Improvement of power conversion efficiency of phthalocyanine/C60 heterojunction solar cells by inserting a lithium phthalocyanine layer at the indium-tin oxide/phthalocyanine interface. Appl. Phys. Lett. 2010, 97, 253306. [Google Scholar] [CrossRef]
  29. Abe, T.; Tobinai, S.; Taira, N.; Chiba, J.; Itoh, T.; Nagai, K. Molecular Hydrogen Evolution by Organic p/n Bilayer Film of Phthalocyanine/Fullerene in the Entire Visible-Light Energy Region. J. Phys. Chem. C 2011, 115, 7701–7705. [Google Scholar] [CrossRef]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Article Metrics

Citations

Article Access Statistics

Journal Statistics
Multiple requests from the same IP address are counted as one view.
Download PDF
Recent Advances in Bio-Inspired Superhydrophobic Coatings Utilizing Hierarchical Nanostructures for Self-Cleaning and Anti-Icing Surfaces
Previous