Morphology engineering of photoelectrodes for efficient photoelectrochemical water splitting

Samuel, Edmund; Joshi, Bhavana; Kim, Min Woo; Swihart, Mark T.; Yoon, Sam S.

doi:10.1016/j.nanoen.2020.104648

Cited by 104 publications

(49 citation statements)

References 210 publications

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“…Using nanostructures is an alternative strategy to achieve high performance since they can overcome the drawbacks of thin films mentioned above owing to their unique nanosize morphologies. [5,36,41,42] So far, many reports have demonstrated the outstanding solar energy conversion performance of semiconductors with nanostructures compared to those without nanostructures. [26,[43][44][45][46] In particular, nanoarray structures, which are large-scale alignment of oriented nanostructure units on the substrate or an arrangement of elements of closely related and systematically varied nanostructures, [47,48] hold great potential in artificial photosynthesis in view of the following key features: 1) array structures can harvest extra light by various strategies such as multiple light scattering and antireflection among the nanostructure units, thereby achieving enhanced light absorption; [47,49,50] 2) nanostructures can shorten the carrier collection distance and increase the proportion of SCR to the bulk for promoting charge separation; [27,36,[51][52][53] 3) nanoarray structures have a higher specific surface area than planar film structures, supplying more chemisorption sites and active sites for catalytic reactions, providing more sites for loading the abiotic or biotic ECs, offering easier access to electrolytes and reactants, and thus accelerating the catalytic kinetics and improving the catalytic selectivity.…”

Section: Advantages Of Nanoarray Structures In Artificial Photosynthesismentioning

confidence: 99%

Nanoarray Structures for Artificial Photosynthesis

Tian

Zhao

et al. 2021

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Conversion and storage of solar energy into fuels and chemicals by artificial photosynthesis has been considered as one of the promising methods to address the global energy crisis. However, it is still far from the practical applications on a large scale. Nanoarray structures that combine the advantages of nanosize and array alignment have demonstrated great potential to improve solar energy conversion efficiency, stability, and selectivity. This article provides a comprehensive review on the utilization of nanoarray structures in artificial photosynthesis of renewable fuels and high value‐added chemicals. First, basic principles of solar energy conversion and superiorities of using nanoarray structures in this field are described. Recent research progress on nanoarray structures in both abiotic and abiotic–biotic hybrid systems is then outlined, highlighting contributions to light absorption, charge transport and transfer, and catalytic reactions (including kinetics and selectivity). Finally, conclusions and outlooks on future research directions of nanoarray structures for artificial photosynthesis are presented.

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Section: Advantages Of Nanoarray Structures In Artificial Photosynthesismentioning

confidence: 99%

Nanoarray Structures for Artificial Photosynthesis

Tian

Zhao

et al. 2021

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“…As a promising approach to renewable energy conversion, solar‐driven photoelectrochemical (PEC) water splitting into hydrogen fuel has triggered many exploring studies. [ 1–3 ] Among the numerous attractive photoelectrodes, the silicon semiconductor has been widely studied and proven to facilitate efficient PEC hydrogen evolution reaction (HER) because of its suitable band gap (1.1 eV) that absorbs sufficient visible light. [ 3–6 ] Generally, Si requires an external cocatalyst for HER because it possesses sluggish surface kinetics.…”

Section: Introductionmentioning

confidence: 99%

Engineering Heterogeneous NiS₂/NiS Cocatalysts with Progressive Electron Transfer from Planar p‐Si Photocathodes for Solar Hydrogen Evolution

Yang

et al. 2021

Small Methods

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The sluggish transfer of electrons from a planar p‐type Si (p‐Si) semiconductor to a cocatalyst restricts the activity of photoelectrochemical (PEC) hydrogen evolution. To overcome such inefficiency, an elegant interphase of the semiconductor/cocatalyst is generally necessary. Hence, in this work, a NiS2/NiS heterojunction (NNH) is prepared in situ and applied to a planar p‐Si substrate as a cocatalyst to achieve progressive electron transfer. The NNH/Si photocathode exhibits an onset potential of +0.28 V versus reversible hydrogen electrode (VRHE) and a photocurrent density of 18.9 mA·cm−2 at 0 VRHE, as well as a 0.9% half‐cell solar‐to‐hydrogen efficiency, which is much superior compared with those of NiS2/Si and NiS/Si photocathodes. The enhanced performance for NNH/Si is attributed to the contact between the sectional n‐type semiconducting NNH and the planar p‐Si semiconductor through a p‐Si/n‐NiS/n‐NiS2 manner that functions as a local pn‐junction to promote electron transfer. Thus, the photogenerated electron is transferred from p‐Si to n‐NiS within NNH as the progressive medium, followed by to Ni2+ and/or S22− of the defect‐rich n‐NiS2 phase as the key active sites. This systematic work may pave the way for planar Si‐based PEC applications of heterogeneous metal sulfide cocatalysts through the progressive transfer of electrons.

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“…Based on these advantages of the graphene acting as a bridge between p-Si and MoP, vertically aligned MoP nanorods (NRs) are directly synthesized on silicon photocathode. To make good use of numerous catalytic sites ascribed to P atoms, we designed a one-dimensional nanostructured MoP with a high surface-to-volume ratio [ 30 , 31 ]. In addition, drastically enhanced anti-reflectance of nanorod-arrays contributes to the overall light absorption of photocathodes.…”

Section: Introductionmentioning

confidence: 99%

Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction

Jun

Choi

et al. 2021

Nano-Micro Lett.

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Highlights MoP nanorod-array catalysts were directly synthesized on graphene passivated silicon photocathodes without secondary phase. Mo-O-C covalent bondings and energy band bending at heterointerfaces facilitate the electron transfer to the reaction sites. Numerous catalytic sites and drastically enhanced anti-reflectance of MoP nanorods contribute to the high solar energy conversion efficiency. Abstract Transition metal phosphides (TMPs) and transition metal dichalcogenides (TMDs) have been widely investigated as photoelectrochemical (PEC) catalysts for hydrogen evolution reaction (HER). Using high-temperature processes to get crystallized compounds with large-area uniformity, it is still challenging to directly synthesize these catalysts on silicon photocathodes due to chemical incompatibility at the heterointerface. Here, a graphene interlayer is applied between p-Si and MoP nanorods to enable fully engineered interfaces without forming a metallic secondary compound that absorbs a parasitic light and provides an inefficient electron path for hydrogen evolution. Furthermore, the graphene facilitates the photogenerated electrons to rapidly transfer by creating Mo-O-C covalent bondings and energetically favorable band bending. With a bridging role of graphene, numerous active sites and anti-reflectance of MoP nanorods lead to significantly improved PEC-HER performance with a high photocurrent density of 21.8 mA cm−2 at 0 V versus RHE and high stability. Besides, low dependence on pH and temperature is observed with MoP nanorods incorporated photocathodes, which is desirable for practical use as a part of PEC cells. These results indicate that the direct synthesis of TMPs and TMDs enabled by graphene interlayer is a new promising way to fabricate Si-based photocathodes with high-quality interfaces and superior HER performance. Graphic Abstract

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Morphology engineering of photoelectrodes for efficient photoelectrochemical water splitting

Cited by 104 publications

References 210 publications

Nanoarray Structures for Artificial Photosynthesis

Nanoarray Structures for Artificial Photosynthesis

Engineering Heterogeneous NiS₂/NiS Cocatalysts with Progressive Electron Transfer from Planar p‐Si Photocathodes for Solar Hydrogen Evolution

Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction

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Morphology engineering of photoelectrodes for efficient photoelectrochemical water splitting

Cited by 104 publications

References 210 publications

Nanoarray Structures for Artificial Photosynthesis

Nanoarray Structures for Artificial Photosynthesis

Engineering Heterogeneous NiS2/NiS Cocatalysts with Progressive Electron Transfer from Planar p‐Si Photocathodes for Solar Hydrogen Evolution

Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction

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Engineering Heterogeneous NiS₂/NiS Cocatalysts with Progressive Electron Transfer from Planar p‐Si Photocathodes for Solar Hydrogen Evolution