| 1. |
- Meng, Qijun, 1990-, et al.
(författare)
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Integrating Cobalt-sites-rich Aza-fused Conjugated Microporous Polymers on BiVO4 for Efficient Photoelectrochemical Water Splitting
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Advanced surface and interface engineering has been demonstrated to be of critical importance for the development of photoanodes for highly efficient photoelectrochemical (PEC) water oxidation. In this study, cobalt-sites-rich aza-fused conjugated microporous polymer was integrated on the nanoporous bismuth vanadate electrode. The hybrid BiVO4/eCMP-Co photoanode exhibited a high photocurrent density of 4.3 mA cm-2 at 1.23 VRHE and a very low onset potential of ~ 0.2 VRHE with an applied bias photon to current efficiency of 1.62% at around 0.6 VRHE. Moreover, studies on charge carrier kinetics showed that eCMP-Co can not only accelerate water oxidation kinetics but also significantly suppress surface recombination, thereby dramatically increasing charge transfer efficiency. These results demonstrate the great potential of conjugated polymers combined with metal coordination as heterogenous catalysts on photoelectrodes in PEC devices.
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| 2. |
- Meng, Qijun, 1990-, et al.
(författare)
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Remarkable synergy of borate and interfacial hole transporter on BiVO4 photoanodes for photoelectrochemical water oxidation
- 2021
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 2:13, s. 4323-4332
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Tidskriftsartikel (refereegranskat)abstract
- Bismuth vanadate (BiVO4) is one of the most fascinating building blocks for the design and assembly of highly efficient artificial photosynthesis devices for solar water splitting. Our recent report has shown that borate treated BiVO4 (B-BiVO4) results in an improved water oxidation performance. In this study, further improvement of both the photoelectrochemical (PEC) activity and stability of B-BiVO4 was successfully achieved by introducing NiFeV LDHs as an oxygen evolution catalyst and interfacial hole transporter. Benefiting from the synergistic effect of co-catalyst and borate pretreatment, the as-prepared NiFeV/B-BiVO4 exhibited a high photocurrent density of 4.6 mA cm−2 at 1.23 VRHE and an outstanding onset potential of ∼0.2 VRHE with good long-term stability. More importantly, NiFeV was found to play a pivotal role in the critically efficient suppression of charge combination on the BiVO4 surface and acceleration of charge transfer rather than a mere electrocatalyst for water oxidation.
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| 3. |
- Meng, Qijun, 1990-
(författare)
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Surface Engineering of BiVO4-based Photoelectrochemical Cells for Water Splitting
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Photoelectrochemical (PEC) water splitting is a promising technology for converting solar energy into green hydrogen. The development of highly efficient, robust and cost-effective photoanodes has been established to be of essential importance for PEC water oxidation. BiVO4 has been deemed as one of the most up-and-coming metal oxide-based photoanode materials for PEC water splitting. Development of new surface engineering techniques for BiVO4 is therefore the subject of this thesis. In Chapter 1, a general introduction that centers on the solar fuel production by BiVO4-based PEC cells is presented. It concerns the working principles of PEC systems, current status of BiVO4-based photoanodes, and modification strategies for enhancement of the PEC activity. In Chapter 2, the characterization methods used in this thesis and the preparation of BiVO4 photoelectrode are introduced. In Chapter 3, a postsynthetic borate treatment is developed to decorate the BiVO4 surface. The PEC performance of as-prepared B-BiVO4 photoanode is evaluated and the mechanism of the PEC enhancement is subsequently investigated. Moreover, the layered double hydroxide-based cocatalyst is integrated with the B-BiVO4 substrate. The synergistic effects of borate treatment and cocatalyst on improvement of the PEC activity are discussed. In Chapter 4, a conjugated microporous polymer-based heterogeneous catalyst is applied to the surface modification of BiVO4. The PEC performance of the BiVO4/eCMP-Co hybrid photoanode is discussed. Furthermore, the origin of the PEC enhancement is investigated by charge kinetics studies.In Chapter 5, a metal-organic complex, cobalt phytate, is introduced on BiVO4 by photo-assisted electrodeposition in the form of an ultra-thin nanolayer. The PEC performance of the BiVO4/CoPhy integrated photoanode and the role of CoPhy in interfacial charge transfer is investigated.
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| 4. |
- Meng, Qijun, 1990-, et al.
(författare)
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Ultra-thin Nanolayers of Photodeposited Cobalt Phytate on BiVO4 for Efficient Photoelectrochemical Water Oxidation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Strategical engineering of semiconducting films by loading co-catalysts is pivotal for optimizing the properties of photoelectrodes used for solar fuel production. In this study, an ultrathin layer of cobalt phytate (CoPhy) was integrated onto the nanoporous bismuth vanadate (BiVO4) photoanode by a simple photo-assisted electrodeposition method. The introduction of CoPhy significantly improved the PEC performance of BiVO4 photoanode, displaying a photocurrent density up to 4.3 mA cm-2 at 1.23 V (vs. reversible hydrogen electrode (RHE), AM 1.5G) and an impressive early onset of potential of ~0.2 VRHE as well as superior stability. Moreover, charge kinetics studies showed that the enhancement in PEC performance by CoPhy is primarily due to the suppression of surface recombination and acceleration of interfacial charge transfer.
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| 5. |
- Yang, Hao, et al.
(författare)
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Intramolecular hydroxyl nucleophilic attack pathway by a polymeric water oxidation catalyst with single cobalt sites
- 2022
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Ingår i: Nature Catalysis. - : Springer Nature. - 2520-1158. ; 5:5, s. 414-429
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Tidskriftsartikel (refereegranskat)abstract
- Exploration of efficient water oxidation catalysts (WOCs) is the primary challenge in conversion of renewable energy into fuels. Here we report a molecularly well-defined heterogeneous WOC with Aza-fused, pi-conjugated, microporous polymer (Aza-CMP) coordinated single cobalt sites (Aza-CMP-Co). The single cobalt sites in Aza-CMP-Co exhibited superior activity under alkaline and near-neutral conditions. Moreover, the molecular nature of the isolated catalytic sites makes Aza-CMP-Co a reliable model for studying the heterogeneous water oxidation mechanism. By a combination of experimental and theoretical results, a pH-dependent nucleophilic attack pathway for O-O bond formation was proposed. Under alkaline conditions, the intramolecular hydroxyl nucleophilic attack (IHNA) process with which the adjacent -OH group nucleophilically attacks Co4+=O was identified as the rate-determining step. This process leads to lower activation energy and accelerated kinetics than those of the intermolecular water nucleophilic attack (WNA) pathway. This study provides significant insights into the crucial function of electrolyte pH in water oxidation catalysis and enhancement of water oxidation activity by regulation of the IHNA pathway.
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