Review on optofluidic microreactors for artificial photosynthesis

Huang, Xiaowen; Wang, Jianchun; Li, Tenghao; Wang, Jianmei; Xu, Min; Yu, Weixing; Abed, Abdel I. El; Zhang, Xuming

doi:10.3762/bjnano.9.5

Cited by 34 publications

(21 citation statements)

References 122 publications

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“…The substrate of photoelectrode is responsible for the growth of semiconductor materials and transfer of electrons in the external circuit. The related half-reaction equations on two electrodes are shown in Equations (2) and (3). The photoelectrodes work as a sunlight absorber, capturing solar energy to driving water splitting.…”

Section: Pec Water Splitting Processmentioning

confidence: 99%

“…[1][2][3][4][5] It is said that the existence of environmental issues partly attributes to the unreasonable use of traditional fossil fuel, such as excessive exploitation and inefficient utilization. Therefore, effective solutions should be proposed to address these issues.…”

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confidence: 99%

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environmental pollution is much worse than imagination. [2][3][4] Photo-electrochemical (PEC) water splitting is a facile photosynthesis route and defined as an electrochemical process which occurs when a semiconductor electrode is under light irradiation in order to convert sunlight into oxygen or hydrogen energy. [1][2][3][4][5] It is said that the existence of environmental issues partly attributes to the unreasonable use of traditional fossil fuel, such as excessive exploitation and inefficient utilization.

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mentioning

confidence: 99%

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Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

et al. 2018

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Photo‐electrochemical (PEC) water splitting, as an essential and indispensable research branch of solar energy applications, has achieved increasing attention in the past decades. Between the two photoelectrodes, the photoanodes for PEC water oxidation are mostly studied for the facile selection of n‐type semiconductors. Initially, the efficiency of the PEC process is rather limited, which mainly results from the existing drawbacks of photoanodes such as instability and serious charge‐carrier recombination. To improve PEC performances, researchers gradually focus on exploring many strategies, among which engineering photoelectrodes with suitable cocatalysts is one of the most feasible and promising methods to lower reaction obstacles and boost PEC water splitting ability. Here, the basic principles, modules of the PEC system, evaluation parameters in PEC water oxidation reactions occurring on the surface of photoanodes, and the basic functions of cocatalysts on the promotion of PEC performance are demonstrated. Then, the key progress of cocatalyst design and construction applied to photoanodes for PEC oxygen evolution is emphatically introduced and the influences of different kinds of water oxidation cocatalysts are elucidated in detail. Finally, the outlook of highly active cocatalysts for the photosynthesis process is also included.

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Section: Pec Water Splitting Processmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

et al. 2018

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“…Optofluidic reactors have intrinsic merits, such as fine flow control, large surface-to-volume ratio, and direct delivery of light to the reaction surface, making them natural photoreactors for photocatalysis [7][8][9][10]. Some studies showed microfluidic methods for achieving good degradation efficiency of polluted water [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Paper-based Photocatalysts Immobilization without Coffee Ring Effect for Photocatalytic Water Purification

Lin

Huang

et al. 2020

Micromachines

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Photocatalytic water purification is important for the degradation of organic pollutants, attracting intensive interests. Photocatalysts are preferred to be immobilized on a substrate in order to reduce the laborious separation and recycling steps. To get uniform irradiation, the photocatalysts are preferred to be even/uniform on the substrate without aggregation. Generally, the “coffee ring effect” occurs on the substrate during solvent evaporation, unfortunately resulting in the aggregation of the photocatalysts. This aggregation inevitably blocks the exposure of active sites, reactant exchange, and light absorption. Here, we reported a paper-based photocatalyst immobilization method to solve the “coffee ring” problem. We also used a “drop reactor” to achieve good photocatalytic efficiency with the advantages of large surface area, short diffusion lengths, simple operation, and uniform light absorption. Compared with the coffee ring type, the paper-based method showed higher water purification efficiency, indicating its potential application value in the future.

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“…They inherit many advantages from microfluidics technology, such as small dimensions, high surface-to-volume (S/V) ratio, easy control of flow rates, short molecular diffusion distance, rapid reaction speed, high reaction efficiency, low reagent consumption, fast heat dissipation, uniform illumination of light, as well as potential portability and disposability [2,16,[21][22][23]. Although a single microreactor has very limited output (~1-100 L/h), the throughput can be scaled up by connecting many devices in parallel, sizing up the reactor dimensions, and even stacking multiple layers of the same devices [14,[24][25][26].Based on the above considerations, this work will incorporate the plasmonic effect into the microreactors so as to exert the full power of both for the enhancement of photodegradation efficiency. The microreactor is bonded on an FTO glass substrate to have a planar reaction chamber, the bottom part of which is decorated by gold nanoparticles (AuNPs) and then covered by a thin TiO 2 layer (Figures 1 and 2).…”

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confidence: 99%

Microfluidic Reactors for Plasmonic Photocatalysis Using Gold Nanoparticles

et al. 2019

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This work reports a microfluidic reactor that utilizes gold nanoparticles (AuNPs) for the highly efficient photocatalytic degradation of organic pollutants under visible light. The bottom of microchamber has a TiO 2 film covering a layer of AuNPs (namely, TiO 2 /AuNP film) deposited on the F-doped SnO 2 (FTO) substrate. The rough surface of FTO helps to increase the surface area and the AuNPs enables the strong absorption of visible light to excite electron/hole pairs, which are then transferred to the TiO 2 film for photodegradation. The TiO 2 film also isolates the AuNPs from the solution to avoid detachment and photocorrosion. Experiments show that the TiO 2 /AuNP film has a strong absorption over 400-800 nm and enhances the reaction rate constant by 13 times with respect to the bare TiO 2 film for the photodegradation of methylene blue. In addition, the TiO 2 /AuNP microreactor exhibits a negligible reduction of photoactivity after five cycles of repeated tests, which verifies the protective function of the TiO 2 layer. This plasmonic photocatalytic microreactor draws the strengths of microfluidics and plasmonics, and may find potential applications in continuous photocatalytic water treatment and photosynthesis. The fabrication of the microreactor uses manual operation and requires no photolithography, making it simple, easy, and of low cost for real laboratory and field tests.2 of 11 resonance (LSPR) due to the collective oscillation of free electrons in response to the excitation of irradiant light. The LSPR effect can drastically enhance the visible response of TiO 2 photocatalysis for solar energy capture, environmental redemption, and selective organic photosynthesis [5,7,9,10]. Moreover, the direct physical contact of the noble metal NPs and the TiO 2 photocatalysts would form a Schottky junction to suppress the recombination of electron-hole pairs [8,11].Typical photodegradation systems involve the suspension of TiO 2 nanopowders in an aqueous solution of a bulky container. With the stirring, the TiO 2 nanopowders have full contact with the dissolved organic pollutants, resulting in a large specific surface area (SSA, defined as the total surface area per unit of mass) and high photodegradation efficiency. However, the suspended TiO 2 nanopowders absorb and scatter light, causing rapid decay, and thus an uneven distribution of the irradiant light. What is more problematic is the requirement of post processing, namely the nanopowders have to be separated from the solution after the reaction [12][13][14]. To avoid these problems, immobilized systems have been developed to fix the TiO 2 photocatalysts on a support, but they tend to have a small SSA and low efficiency [15].Microfluidic reactors have attracted much attention and have been proposed to tackle the drawbacks of photocatalytic processes [14,[16][17][18][19][20]. They inherit many advantages from microfluidics technology, such as small dimensions, high surface-to-volume (S/V) ratio, easy control of flow rates, short molecular diffusion distance,...

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Review on optofluidic microreactors for artificial photosynthesis

Cited by 34 publications

References 122 publications

Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

Paper-based Photocatalysts Immobilization without Coffee Ring Effect for Photocatalytic Water Purification

Microfluidic Reactors for Plasmonic Photocatalysis Using Gold Nanoparticles

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