Defects Engineering in Photocatalytic Water Splitting Materials

Liu, Junying; Wei, Zhidong; Shangguan, Wenfeng

doi:10.1002/cctc.201901579

Cited by 106 publications

(91 citation statements)

References 98 publications

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“…[ 40 ] Fine‐tuning of defective surface exhibits a prominent modulation in geometries, electronic properties, atomic coordination and charge separation of nanomaterials, which substantially interferes the catalytic and reactive performance. [ 41,42 ] Profiting from these features, the intentional engineering of surface vacancies has held enormous passion in energy harvest and conversion. However, the creation of desirable vacancies is complicated as the introduction of surface deficiency tends to induce the unexpected bulk defects, which is detrimental to the photocatalysts, especially in promoting the photoexcited charge recombination during photocatalysis.…”

Section: Defect Engineeringmentioning

confidence: 99%

Engineering 2D Photocatalysts toward Carbon Dioxide Reduction

Zhou

Wang

Huang

et al. 2021

Advanced Energy Materials

158

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As a way to drive chemical reactions by renewable solar energy, photocatalytic technology is an appealing strategy for carbon recycle and value‐added CO2 utilization mimicking the natural photosynthetic system to remedy energy and environmental problems. During the recent decades of exploration, extensive research has been reported on 2D nanomaterials in photocatalytic CO2 reduction because of their unique structural properties. This review highlights the ongoing development of modification strategies for 2D nanomaterials from the viewpoints of defect engineering, surface modification, and hybrid construction, following the sequence of inside‐to‐outside design of the photocatalysts. These methodologies can expand the scope of light absorption, promote the separation of photogenerated charge carriers, and enhance the adsorption and activation of CO2, thus effectively improve the photocatalytic efficiency. The future challenges and opportunities for developing modified 2D photocatalysts are also discussed. It is hoped that this review can provide useful guidelines toward further research on 2D nanocatalysis for CO2 photocatalytic conversion.

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Section: Defect Engineeringmentioning

confidence: 99%

Engineering 2D Photocatalysts toward Carbon Dioxide Reduction

Zhou

Wang

Huang

et al. 2021

Advanced Energy Materials

158

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“…However, if the charge carriers cannot transfer rapidly due to intrinsic electrical conductivity limitations of the materials, the excitons relax to the ground state and generate heat or light (Figure 1(iii)). Additionally, charge carriers can be trapped in trap states, such as antisites, interstitials, and vacancy defects (Figure 1 (iv)) [5][6][7][8][9]. The surface contains a high density of vacancy defects because the bulk crystalline structure does not elongate further.…”

Section: Photogenerated Charge Carriers Dynamicsmentioning

confidence: 99%

“…The surface chemical structure of materials has different chemical and electronic properties from the bulk crystalline structure, which generates charged dangling bonds, various coordination states, and different chemical potential. The charged dangling bonds on the surface induce a surface dipole, and induce the Fermi level shift at the surface to produce a built-in potential [7,8]. Also, the facets of the surface have distinctive atomic arrangements, and coordination states, and possess the different chemical and electronic properties.…”

Section: Surface States At the Solid-liquid Interface For Charge Tranmentioning

confidence: 99%

Understanding Surface Modulation to Improve the Photo/Electrocatalysts for Water Oxidation/Reduction

Cho

Lee

2020

Molecules

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Water oxidation and reduction reactions play vital roles in highly efficient hydrogen production conducted by an electrolyzer, in which the enhanced efficiency of the system is apparently accompanied by the development of active electrocatalysts. Solar energy, a sustainable and clean energy source, can supply the kinetic energy to increase the rates of catalytic reactions. In this regard, understanding of the underlying fundamental mechanisms of the photo/electrochemical process is critical for future development. Combining light-absorbing materials with catalysts has become essential to maximizing the efficiency of hydrogen production. To fabricate an efficient absorber-catalysts system, it is imperative to fully understand the vital role of surface/interface modulation for enhanced charge transfer/separation and catalytic activity for a specific reaction. The electronic and chemical structures at the interface are directly correlated to charge carrier movements and subsequent chemical adsorption and reaction of the reactants. Therefore, rational surface modulation can indeed enhance the catalytic efficiency by preventing charge recombination and prompting transfer, increasing the reactant concentration, and ultimately boosting the catalytic reaction. Herein, the authors review recent progress on the surface modification of nanomaterials as photo/electrochemical catalysts for water reduction and oxidation, considering two successive photogenerated charge transfer/separation and catalytic chemical reactions. It is expected that this review paper will be helpful for the future development of photo/electrocatalysts.

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“…HRTEM image also revealed that a disordered layer appeared around NiO due to the existence of oxygen vacancy. [ 45–47 ] The corresponding elemental mappings of partial SEM image revealed the NiTCPP molecule was homogeneously loaded on the surface of NiO (Figure 1f). To further confirm the integrated system has been successfully prepared, UV–visible diffuse reflectance spectra (DRS) were performed and displayed in Figure 1g.…”

Section: Figurementioning

confidence: 99%

“…In addition, electron spin resonance (ESR) spectroscopy can provide the information of the unpaired electrons and the relative concentration of defect can be obtained according to different g values and intensities. [ 46 ] As shown in Figure S5 (Supporting Information), the ESR signal observed in different NiO samples with g = 2.001 can be assigned to oxygen vacancy. [ 56 ] The signal intensity increased with the increased calcination temperature, meaning much more oxygen vacancies were introduced.…”

Section: Figurementioning

confidence: 99%

Enhancing Charge Separation through Oxygen Vacancy‐Mediated Reverse Regulation Strategy Using Porphyrins as Model Molecules

Yin

Ning

Zhang

et al. 2020

Small

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Up to now, substantial efforts have been devoted to enhancing charge separation by heterostructure construction, [7] cocatalyst loading, [8-10] element doping [11] and polarization, [12] among which coupling co-catalysts with semiconductors is a common and widespread method to improve the sluggish reaction kinetics [13] or influence the band bending of semiconductor to enhance charge separation. [14] However, the introduction of co-catalysts may cause unwanted light absorption and increase the possibility of recombination of photogenerated electrons and holes at the semiconductor/co-catalyst junction. [13,15] Therefore, developing highly efficient regulation methods is quite desirable and imperative for improving charge separation. Typically, electron-hole pairs generated by light absorption need to be separated and transferred to the surface of photoelectrodes to carry out redox reactions with adsorbed donor or acceptor molecules. As for photocathode, most previous studies focused on the electron transfer while much less attention has been paid to the regulation of holes in the construction of photocathodes, especially in PEC systems. In fact, compared with the recognized fast enough electron transfer process, the hole transport is a relative slow process, which determines the high charge recombination rate. [16-18] Xie et al. [16] reported that a homogeneous molecular co-catalyst influenced the hole transport process and therefore enhanced photocatalytic hydrogen production efficiency of the photocatalysis. Feldmann et al. [17] explored a redox couple to efficiently relay the hole from the semiconductor to the scavenger and lead to increased hydrogen production rate. These examples imply that modulating hole transfer is indeed a potentially effective method to enhance charge separation. Such modulation to facilitate charge separation also has been applied in inverted solar cells aiming at getting higher solar conversion efficiency. [19,20] Recently, defect engineering has been taken into consideration and demonstrated to be an effective method in tuning properties of electrocatalysts and photo(electro)catalysts. [21-23] Oxygen vacancy (V O), as one of the intrinsic defects in metal oxides, plays an essential role in improving the electronic Highly efficient charge separation has been demonstrated as one of the most significant steps playing decisive roles in enhancing the overall efficiency of photoelectrochemical (PEC) processes. In this study, by employing 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin-Ni (NiTCPP) as a prototype, an oxygen vacancy (Vo)-mediated reverse regulation strategy is proposed for tuning hole transfer, which in turn can accelerate the transport of electrons and thus enhancing charge separation. The optimal NiO/NiTCPP system exhibits much higher (≈40 times) photocurrent and longer (≈13 times) lifetime of charge carriers compared with those of pure NiTCPP. Furthermore, the electron transfer kinetic rate constant (K eff) is quantitatively determined by an efficient scanning photoelectroc...

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Defects Engineering in Photocatalytic Water Splitting Materials

Cited by 106 publications

References 98 publications

Engineering 2D Photocatalysts toward Carbon Dioxide Reduction

Engineering 2D Photocatalysts toward Carbon Dioxide Reduction

Understanding Surface Modulation to Improve the Photo/Electrocatalysts for Water Oxidation/Reduction

Enhancing Charge Separation through Oxygen Vacancy‐Mediated Reverse Regulation Strategy Using Porphyrins as Model Molecules

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