High-efficiency unbiased water splitting with photoanodes harnessing polycarbazole hole transport layers

Yang, Jin Wook; Ji, Su Geun; Jeong, Chang-Seop; Kim, Jaehyun; Kwon, Hee Ryeong; Lee, Tae Hyung; Lee, Sol A; Cheon, Woo Seok; Lee, Seokju; Lee, Hyungsoo; Kwon, Min Sang; Moon, Jooho; Kim, Jin Young; Jang, Ho Won

doi:10.1039/d3ee03353h

“…42 In recent years, various strategies have been employed to overcome these obstacles, 53 including nanostructures fabrication, elements doping, surface passivation, heterojunction design, etc. State-of-the-art BiVO 4 photoanodes have achieved a remarkable water oxidation photocurrent density of 6.66 mA cm −2 at 1.23 V RHE , 54 close to their theoretical limit of 7.5 mA cm −2 .…”

Section: Other Reactionssupporting

confidence: 58%

Advancing Silicon-Based Photoelectrodes toward Practical Artificial Photosynthesis

Wang,

Liu,

Wang

et al. 2024

Acc. Mater. Res.

1

0

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Metrics & MoreArticle Recommendations CONSPECTUS: Artificial photosynthesis is a sustainable technology to convert solar energy into storable chemicals or fuels, which potentially paves the way for coping with the greenhouse gas emission and growing energy demand. Semiconductor photoelectrodes are vital constituents in artificial photosynthesis systems. Among them, silicon (Si) is extensively employed due to its earth abundance, suitable band gap, and low cost. However, Si-based photoelectrodes suffer from insufficient photovoltage, serious interfacial charge recombination, sluggish reaction kinetics, and low stability in electrolyte.Numerous strategies have been proposed to address these challenges. Si-based photoelectrodes comprising buried junctions, passivation/protective layers, and electrocatalysts as the main components have thus been developed. Unfortunately, several issues persist: (1) the additional defect state at the newly formed interfaces;(2) the contradiction between adequate passivation/protection and sufficient charge transfer;(3) the parasitic light absorption of electrocatalyst; and (4) the lack of compatibility with different application scenarios. Therefore, it is paramount to meticulously balance the functionalities and potential detrimental impacts brought about by different components to govern the photoelectrode design. This Account describes recent advances in Si-based photoelectrode design toward high efficiency, excellent stability, and practical applications in artificial photosynthesis. The charge utilization efficiency is determined by charge generation, separation, and transport processes, which could be simultaneously improved by the careful designs of homo/heterojunctions, bifacial passivation, and illumination-reaction decoupling. The above methods have been proven to be efficient, as through them we have obtained benchmark Si-based photocathodes. Apart from efficiency, stability is another key factor. We explored the charge transport and deactivation mechanisms of the traditional metal oxide protective layers, varied the coverage and surface energy of organic protective layers to control the flux of photogenerated charge, and discussed the merits of metal protective layers in illumination-reaction decoupled photoelectrodes. Moreover, the versatility of our Si-based photoelectrodes in unbiased water splitting with separated and integrated configurations, as well as in CO 2 reduction with H-cell and flow cell, is proposed. Finally, the key challenges and future perspectives toward practical artificial synthesis are suggested. Our collective work outlines strategies for efficient and stable Si-based photoelectrodes. These general methods may be applicable to other semiconductor photoelectrodes for artificial synthesis.

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Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation

Yang,

Deng,

Lei

et al. 2024

Angewandte Chemie

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Bismuth vanadate ranks among the most promising photoanodes for photoelectrochemical water splitting. Nonetheless, slow charge separation and transport are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO. Under standard one sun illumination, the Fe‐N co‐doped BVO photoanode (Fe‐N‐BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm‐2 at 1.23 V vs RHE after modified a surface co‐catalyst. By contrast, much lower photocurrent density is obtained for the N‐doped and Fe‐doped BVO with separated N and Fe precursors. The detailed characterizations show that the high activity of the Fe‐N‐BVO is attributed to the enhanced photo‐induced bulk charge separation and the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe‐N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites.

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Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation

Yang,

Deng,

Lei

et al. 2024

Angew Chem Int Ed

1

0

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Bismuth vanadate ranks among the most promising photoanodes for photoelectrochemical water splitting. Nonetheless, slow charge separation and transport are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO. Under standard one sun illumination, the Fe‐N co‐doped BVO photoanode (Fe‐N‐BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm‐2 at 1.23 V vs RHE after modified a surface co‐catalyst. By contrast, much lower photocurrent density is obtained for the N‐doped and Fe‐doped BVO with separated N and Fe precursors. The detailed characterizations show that the high activity of the Fe‐N‐BVO is attributed to the enhanced photo‐induced bulk charge separation and the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe‐N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites.

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High-efficiency unbiased water splitting with photoanodes harnessing polycarbazole hole transport layers

Abstract: Conformal heterojunction of a competent hole transport layer onto the nanoporous BiVO4 photoanode is highly challenging despite its promise for unbiased photoelectrochemical (PEC) water splitting. Here, we grow a nanoscale...

Cited by 8 publications

References 61 publications

Advancing Silicon-Based Photoelectrodes toward Practical Artificial Photosynthesis

Advancing Silicon-Based Photoelectrodes toward Practical Artificial Photosynthesis

Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation

Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation

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High-efficiency unbiased water splitting with photoanodes harnessing polycarbazole hole transport layers

Abstract: Conformal heterojunction of a competent hole transport layer onto the nanoporous BiVO4 photoanode is highly challenging despite its promise for unbiased photoelectrochemical (PEC) water splitting. Here, we grow a nanoscale...

Cited by 8 publications

References 61 publications

Advancing Silicon-Based Photoelectrodes toward Practical Artificial Photosynthesis

Advancing Silicon-Based Photoelectrodes toward Practical Artificial Photosynthesis

Fe−N Co‐Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation

Fe−N Co‐Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation

Contact Info

Product

Resources

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Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation

Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation