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Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Photocatalysis".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 30382

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Prof. Dr. Tzu-Hsuan Chiang

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Guest Editor

Department of Energy Engineering, National United University, Lienda, Miaoli 36063, Taiwan
Interests: electrocatalysts and photocatalysts for overall water splitting and CO2 reduction; electrocatalysts for Zn–air batteries; photocatalysts for dye degradation

Special Issue Information

Dear Colleagues,

The development of highly efficient photocatalytic water splitting through an advanced cocatalyst and photocatalyst system has attracted considerable interest. The construction of an efficient cocatalyst and photocatalyst system is essential for promoting surface catalytic reactions. First, the photocatalysts should possess a band gap to match not only an efficient light absorption wavelength but also suitable conduction band and valence band levels for water-splitting redox reactions. Then, loading cocatalysts on to the surface of a photocatalyst to provide active sites accelerates the photocatalytic reaction and consequently improves the efficiency of overall water splitting. It should be emphasized that the processes of charge separation and surface catalytic reactions are synergistically correlated. In addition, the heterostructures, nanostructures, and nanosheets of photocatalysts can improve light absorption characteristics and shorten electron and hole migration paths to the surface of photocatalysts. The design of cocatalysts and photocatalysts structures is important for charge separation and surface catalytic reactions and should be discussed for the construction of highly efficient photocatalyst systems.

This Special Issue aims to cover the most recent progress and the advances in the field of cocatalyst and photocatalyst composites. This includes, but is not limited to, cocatalysts (e.g., noble, non-noble metal, and metal oxide cocatalysts), photocatalysts (e.g., nanostructures, 2D and 3D structures, and nanosheets), and photocatalyst composites (e.g., Z-scheme, graphene based, heterostructures, and heterojunction).

Prof. Dr. Tzu-Hsuan Chiang
Guest Editor

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Keywords

cocatalysts
photocatalytic water splitting
heterostructures
Z-scheme
photocatalyst composites

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Published Papers (9 papers)

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Research

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11 pages, 2530 KiB

Open AccessArticle

Exploring the Potential of Water-Soluble Cu(II) Complexes with MPA–CdTe Quantum Dots for Photoinduced Electron Transfer

by Niharika Krishna Botcha, Rithvik R. Gutha, Seyed M. Sadeghi and Anusree Mukherjee

Catalysts 2022, 12(4), 422; https://doi.org/10.3390/catal12040422 - 9 Apr 2022

Cited by 2 | Viewed by 2027

Abstract

Three water-soluble copper complexes based on the amine/pyridine functionalities were investigated, along with quantum dots, as a catalyst–photosensitizer assembly, respectively, for fundamental understanding of photoinduced electron transfer. Luminescence quenching and lifetime measurements were performed to try and establish the actual process that leads to the quenching, such as electron transfer, energy transfer, or complex formation (static quenching). Cyclic voltammetry and dynamic light scattering experiments were also performed. Irrespective of the similar reduction potentials of the three complexes, very different photoluminescence properties were observed. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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11 pages, 2426 KiB

Open AccessArticle

Fabrication of Ni₂P Cocatalyzed CdS Nanorods with a Well-Defined Heterointerface for Enhanced Photocatalytic H₂ Evolution

by Mengdie Cai, Siyu Cao, Zhenzhen Zhuo, Xue Wang, Kangzhong Shi, Qin Cheng, Zhaoming Xue, Xi Du, Cheng Shen, Xianchun Liu, Rui Wang, Lu Shi and Song Sun

Catalysts 2022, 12(4), 417; https://doi.org/10.3390/catal12040417 - 8 Apr 2022

Cited by 22 | Viewed by 3522

Abstract

Developing non-noble metal photocatalysts for efficient photocatalytic hydrogen evolution is crucial for exploiting renewable energy. In this study, a photocatalyst of Ni₂P/CdS nanorods consisting of cadmium sulfide (CdS) nanorods (NRs) decorated with Ni₂P nanoparticles (NPs) was fabricated using an in-situ solvothermal method with red phosphor (P) as the P source. Ni₂P NPs were tightly anchored on the surface of CdS NRs to form a core-shell structure with a well-defined heterointerface, aiming to achieve a highly efficient photocatalytic H₂ generation. The as-synthesized 2%Ni₂P/CdS NRs photocatalyst exhibited the significantly improved photocatalytic H₂ evolution rate of 260.2 μmol∙h⁻¹, more than 20 folds higher than that of bare CdS NRs. Moreover, the as-synthesized 2%Ni₂P/CdS NRs photocatalyst demonstrated an excellent stability, even better than that of Pt/CdS NRs. The photocatalytic performance enhancement was ascribed to the core-shell structure with the interfacial Schottky junction between Ni₂P NPs and CdS NRs and the accompanying fast and effective photogenerated charge carriers’ separation and transfer. This work provides a new strategy for designing non-noble metal photocatalysts to replace the noble catalysts for photocatalytic water splitting. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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11 pages, 2630 KiB

Open AccessArticle

First-Principles Study of Electronic and Optical Properties of Two-Dimensional WSSe/BSe van der Waals Heterostructure with High Solar-to-Hydrogen Efficiency

by Zhengyang Zhu, Kai Ren, Huabing Shu, Zhen Cui, Zhaoming Huang, Jin Yu and Yujing Xu

Catalysts 2021, 11(8), 991; https://doi.org/10.3390/catal11080991 - 18 Aug 2021

Cited by 21 | Viewed by 3854

Abstract

In this paper, the optical and electronic properties of WSSe/BSe heterostructure are investigated by first-principles calculations. The most stable stacking pattern of the WSSe/BSe compounds is formed by van der Waals interaction with a thermal stability proved by ab initio molecular dynamics simulation. The WSSe/BSe heterostructure exhibits a type-I band alignment with direct bandgap of 2.151 eV, which can improve the effective recombination of photoexcited holes and electrons. Furthermore, the band alignment of the WSSe/BSe heterostructure can straddle the water redox potential at pH 0–8, and it has a wide absorption range for visible light. In particular, the solar-to-hydrogen efficiency of the WSSe/BSe heterostructure is obtained at as high as 44.9% at pH 4 and 5. All these investigations show that the WSSe/BSe heterostructure has potential application in photocatalysts to decompose water. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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13 pages, 3009 KiB

Open AccessArticle

Ab Initio Studies of Bimetallic-Doped {0001} Hematite Surface for Enhanced Photoelectrochemical Water Splitting

by Joseph Simfukwe, Refilwe Edwin Mapasha, Artur Braun and Mmantsae Diale

Catalysts 2021, 11(8), 940; https://doi.org/10.3390/catal11080940 - 3 Aug 2021

Cited by 5 | Viewed by 2446

Abstract

First-principles calculations based on density functional theory (DFT) were carried out to study the energetic stability and electronic properties of a bimetallic-doped α-Fe₂O₃ photoanode surface with (Zn, Ti) and (Zn, Zr) pairs for enhanced PEC water splitting. The doped systems showed negative formation energies under both O-rich and Fe-rich conditions which make them thermodynamically stable and possible to be synthesised. It is found that in a bimetallic (Zn, Ti)-doped system, at a doping concentration of 4.20% of Ti, the bandgap decreases from 2.1 eV to 1.80 eV without the formation of impurity states in the bandgap. This is favourable for increased photon absorption and efficient movement of charges from the valance band maximum (VBM) to the conduction band minimum (CBM). In addition, the CBM becomes wavy and delocalised, suggesting a decrease in the charge carrier mass, enabling electron–holes to successfully diffuse to the surface, where they are needed for water oxidation. Interestingly, with single doping of Zr at the third layer (L3) of Fe atoms of the {0001} α-Fe₂O₃ surface, impurity levels do not appear in the bandgap, at both concentrations of 2.10% and 4.20%. Furthermore, at 2.10% doping concentration of α-Fe₂O₃ with Zr, CBM becomes delocalised, suggesting improved carrier mobility, while the bandgap is altered from 2.1 eV to 1.73 eV, allowing more light absorption in the visible region. Moreover, the photocatalytic activities of Zr-doped hematite could be improved further by codoping it with Zn because Zr is capable of increasing the conductivity of hematite by the substitution of Fe³⁺ with Zr⁴⁺, while Zn can foster the surface reaction and reduce quick recombination of the electron–hole pairs. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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14 pages, 6386 KiB

Open AccessFeature PaperArticle

Improving Photoelectrochemical Activity of ZnO/TiO₂ Core–Shell Nanostructure through Ag Nanoparticle Integration

by Zeli Wang, Zhen Chen, Jiadong Dan, Weiqiang Chen, Chenghang Zhou, Zexiang Shen, Tze Chien Sum and Xue-Sen Wang

Catalysts 2021, 11(8), 911; https://doi.org/10.3390/catal11080911 - 28 Jul 2021

Cited by 7 | Viewed by 3618

Abstract

In solar energy harvesting using solar cells and photocatalysts, the photoexcitation of electrons and holes in semiconductors is the first major step in the solar energy conversion. The lifetime of carriers, a key factor determining the energy conversion and photocatalysis efficiency, is shortened mainly by the recombination of photoexcited carriers. We prepared and tested a series of ZnO/TiO₂-based heterostructures in search of designs which can extend the carrier lifetime. Time-resolved photoluminescence tests revealed that, in ZnO/TiO₂ core–shell structure the carrier lifetime is extended by over 20 times comparing with the pure ZnO nanorods. The performance improved further when Ag nanoparticles were integrated at the ZnO/TiO₂ interface to construct a Z-scheme structure. We utilized these samples as photoanodes in a photoelectrochemical (PEC) cell and analyzed their solar water splitting performances. Our data showed that these modifications significantly enhanced the PEC performance. Especially, under visible light, the Z-scheme structure generated a photocurrent density 100 times higher than from the original ZnO samples. These results reveal the potential of ZnO-Ag-TiO₂ nanorod arrays as a long-carrier-lifetime structure for future solar energy harvesting applications. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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19 pages, 5931 KiB

Open AccessFeature PaperArticle

Effects of RhCrO_x Cocatalyst Loaded on Different Metal Doped LaFeO₃ Perovskites with Photocatalytic Hydrogen Performance under Visible Light Irradiation

by Tzu Hsuan Chiang, Gujjula Viswanath and Yu-Si Chen

Catalysts 2021, 11(5), 612; https://doi.org/10.3390/catal11050612 - 11 May 2021

Cited by 12 | Viewed by 3266

Abstract

Photocatalytic hydrogen (H₂) production by water splitting provides an alternative to fossil fuels using clean and renewable energy, which gives important requirements about the efficiency of photocatalysts, co-catalysts, and sacrificial agents. To achieve higher H₂ production efficiencies from water splitting, the study uses different metals such as yttrium (Y), praseodymium (Pr), magnesium (Mg), Indium (In), calcium (Ca), europium (Eu), and terbium (Tb) doped lanthanum iron oxide (LaFeO₃) perovskites. They were synthesized using a co-precipitate method in a citric acid solution, which was loaded with the rhodium chromium oxide (RhCrO_x) cocatalysts by an impregnation method along with a detailed investigation of photocatalytic hydrogen evolution performance. Photoluminescence (PL) and UV–Vis diffuse reflectance spectra (DRS) measured the rate of electron–hole recombination for RhCrO_x/Pr-LaFeO₃ photocatalysts, and X-ray powder diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectra (XPS) analyzed their characteristics. The experimental results obtained show that the samples with 0.5 wt.% RhCrO_x loading and 0.1 M Pr-doped LaFeO₃ calcined at a temperature of 700 °C (0.1Pr-LaFeO₃-700) exhibited the highest photocatalytic H₂ evolution rate of 127 µmol h⁻¹ g⁻¹, which is 34% higher photocatalytic H₂ evolution performance than undoped LaFeO₃ photocatalysts (94.8 μmol h⁻¹ g⁻¹). A measure of 20% of triethanolamine (TEOA) enabled a high hole capture capability and promoted 0.1-Pr-LaFeO₃-700 to get the highest H₂ evolution rate. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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12 pages, 2381 KiB

Open AccessArticle

Oxygen Evolution Activity of LaNbN₂O-Based Photocatalysts Obtained from Nitridation of a Precursor Oxide Structurally Modified by Incorporating Volatile Elements

by Shwetharani Ramu, Takashi Hisatomi and Kazunari Domen

Catalysts 2021, 11(5), 566; https://doi.org/10.3390/catal11050566 - 29 Apr 2021

Viewed by 2666

Abstract

The perovskite-type oxynitride LaNbN₂O is a photocatalyst that can evolve oxygen from aqueous solutions in response to long-wavelength visible light. However, it is challenging to obtain active LaNbN₂O because of the facile reduction of Nb⁵⁺ during the nitridation of the precursor materials. The present study attempted to synthesize a perovskite-type oxide La_0.6Na_0.4Zn_0.4Nb_0.6O₃, containing equimolar amounts of La³⁺ and Nb⁵⁺ in addition to volatile Na⁺ and Zn²⁺, followed by the nitridation of this oxide to generate LaNbN₂O. The obtained oxide was not the intended single-phase material but rather comprised a cuboid perovskite-type oxide similar to La_0.5Na_0.5Zn_0.33Nb_0.67O₃ along with spherical LaNbO₄ particles and other impurities. A brief nitridation was found to form a LaNbN₂O-like shell structure having a light absorption onset of approximately 700 nm on the cuboid perovskite-type oxide particles. This LaNbN₂O-based photocatalyst, when loaded with a CoO_x cocatalyst, exhibited an apparent quantum yield of 1.7% at 420 nm during oxygen evolution reaction from an aqueous AgNO₃ solution. This was more than double the values obtained from the nitridation products of LaNbO₄ and LaKNaNbO₅. The present work demonstrates a new approach to the design of precursor oxides that yield highly active LaNbN₂O and suggests opportunities for developing efficient Nb-based perovskite oxynitride photocatalysts. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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13 pages, 4899 KiB

Open AccessFeature PaperArticle

Nanoscale Multidimensional Pd/TiO₂/g-C₃N₄ Catalyst for Efficient Solar-Driven Photocatalytic Hydrogen Production

by Ting-Han Lin, Yin-Hsuan Chang, Kuo-Ping Chiang, Jer-Chyi Wang and Ming-Chung Wu

Catalysts 2021, 11(1), 59; https://doi.org/10.3390/catal11010059 - 4 Jan 2021

Cited by 14 | Viewed by 4415

Abstract

Solar-to-fuel conversion is an innovative concept for green energy, attracting many researchers to explore them. Solar-driven photocatalysts have become an essential solution to provide valuable chemicals like hydrogen, hydrocarbon, and ammonia. For sustainable stability under solar irradiation, titanium dioxide is regarded as an acceptable candidate, further showing excellent photocatalytic activity. Incorporating the photo-sensitizers, including noble metal nanoparticles and polymeric carbon-based material, can improve its photoresponse and facilitate the electron transfer and collection. In this study, we synthesized the graphitic carbon nitride (g-C₃N₄) nanosheet incorporated with high crystalline TiO₂ nanofibers (NF) as 1D/2D heterostructure catalyst for photocatalytic water splitting. The microstructure, optical absorption, crystal structure, charge carrier dynamics, and specific surface area were characterized systematically. The low bandgap of 2D g-C₃N₄ nanosheets (NS) as a sensitizer improves the specific surface area and photo-response in the visible region as the incorporated amount increases. Because of the band structure difference between TiO₂ and g-C₃N₄, constructing the heterojunction formation, the superior separation of electron-hole is observed. The detection of reactive oxygen species and photo-assisted Kelvin probe microscopy are conducted to investigates the possible charge migration. The highest photocatalytic hydrogen production rate of Pd/TiO₂/g-C₃N₄ achieves 11.62 mmol·h⁻¹·g⁻¹ under xenon lamp irradiation. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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Review

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29 pages, 9188 KiB

Open AccessReview

Atomically Dispersed Catalytic Sites: A New Frontier for Cocatalyst/Photocatalyst Composites toward Sustainable Fuel and Chemical Production

by Shuping Zhang, Bing Bai, Jia Liu and Jiatao Zhang

Catalysts 2021, 11(10), 1168; https://doi.org/10.3390/catal11101168 - 27 Sep 2021

Cited by 7 | Viewed by 3003

Abstract

Photocatalysis delivers a promising pathway toward the clean and sustainable energy supply of the future. However, the inefficiency of photon absorption, rapid recombination of photogenerated electron-hole pairs, and especially the limited active sites for catalytic reactions result in unsatisfactory performances of the photocatalytic materials. Single-atom photocatalysts (SAPCs), in which metal atoms are individually isolated and stably anchored on support materials, allow for maximum atom utilization and possess distinct photocatalytic properties due to the unique geometric and electronic features of the unsaturated catalytic sites. Very recently, constructing SAPCs has emerged as a new avenue for promoting the efficiency of sustainable production of fuels and chemicals via photocatalysis. In this review, we summarize the recent development of SAPCs as a new frontier for cocatalyst/photocatalyst composites in photocatalytic water splitting. This begins with an introduction on the typical structures of SAPCs, followed by a detailed discussion on the synthetic strategies that are applicable to SAPCs. Thereafter, the promising applications of SAPCs to boost photocatalytic water splitting are outlined. Finally, the challenges and prospects for the future development of SAPCs are summarized. Full article

(This article belongs to the Special Issue Advances in Water-Splitting Activity of Highly Efficient Cocatalyst/Photocatalyst Composites)

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