| 1. |
- Fan, Ke, et al.
(författare)
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Sacrificial W Facilitates Self-Reconstruction with Abundant Active Sites for Water Oxidation
- 2022
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Ingår i: Marine and Petroleum Geology. - : Wiley. - 0264-8172 .- 1873-4073. ; 138
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Tidskriftsartikel (refereegranskat)abstract
- Water oxidation is an important reaction for multiple renewable energy conversion and storage-related devices and technologies. High-performance and stable electrocatalysts for the oxygen evolution reaction (OER) are urgently required. Bimetallic (oxy)hydroxides have been widely used in alkaline OER as electrocatalysts, but their activity is still not satisfactory due to insufficient active sites. In this research, A unique and efficient approach of sacrificial W to prepare CoFe (oxy)hydroxides with abundant active species for OER is presented. Multiple ex situ and operando/in situ characterizations have validated the self-reconstruction of the as-prepared CoFeW sulfides to CoFe (oxy) hydroxides in alkaline OER with synchronous W etching. Experiments and theoretical calculations show that the sacrificial W in this process induces metal cation vacancies, which facilitates the in situ transformation of the intermediate metal hydroxide to CoFe-OOH with more high-valence Co(III), thus creating abundant active species for OER. The Co(III)-rich environment endows the in situ formed CoFe oxyhydroxide with high catalytic activity for OER on a simple flat glassy carbon electrode, outperforming those not treated by the sacrificial W procedure. This research demonstrates the influence of etching W on the electrocatalytic performance, and provides a low-cost means to improve the active sites of the in situ self-reconstructed bimetallic oxyhydroxides for OER.
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| 2. |
- Shang, Yu, et al.
(författare)
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Pyrrolic N or pyridinic N : The active center of N-doped carbon for CO2 reduction
- 2022
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Ingår i: Cuihuà xuébào. - : Elsevier BV. - 0253-9837 .- 1872-2067. ; 43:9, s. 2405-2413
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Tidskriftsartikel (refereegranskat)abstract
- Pyridinic N is widely regarded as the active center while pyrrolic N has low-activity in metal-free N-doped carbon for electrocatalytic CO2 reduction reaction (CO2RR) to CO, but this viewpoint remains open to question. In this study, through density functional theoretical calculations, we first illustrate that the intrinsic activity of pyrrolic N is high enough for effectively catalyzing CO2RR, however, due to the interplay with the neighboring pyridinic N sites, the activity of pyrrolic N is dramatically suppressed. Then, experimentally, metal-free N-doped carbon spheres (NCS) electrocatalysts without significant pyridinic N content are prepared for CO2RR. The pyrrolic N in NCS shows a direct-positive correlation with the performance for CO2RR, representing the active center with high activity. The optimum NCS could produce syngas with a wide range of CO/H-2 ratio (0.09 to 12) in CO2RR depending on the applied potential, meanwhile, the best selectivity of 71% for CO can be obtained. Intentionally adding a small amount of pyridinic N to the optimum NCS dramatically decreases the activity for CO2RR, further verifying the suppressed activity of pyrrolic N sites by the neighboring pyridinic N sites. This work reveals the interaction between a variety of N species in N-doped carbon, and the potential of pyrrolic N as the new type of active site for electrocatalysts, which can improve our understanding of the electrocatalysis mechanism and be helpful for the rational design of high-efficient electrocatalysts.
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| 3. |
- Xu, Suxian, et al.
(författare)
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Immobilization of Iron Phthalocyanine on Pyridine-Functionalized Carbon Nanotubes for Efficient Nitrogen Reduction Reaction
- 2022
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 12:9, s. 5502-5509
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Tidskriftsartikel (refereegranskat)abstract
- An electrochemical nitrogen reduction reaction (NRR) under mild conditions offers a promising alternative to the traditional Haber-Bosch process in converting abundant nitrogen (N2) to high value-added ammonia (NH3). In this work, iron phthalocyanine (FePc) was homogeneously immobilized on pyridine-functionalized carbon nanotubes to form a well-tuned electrocatalyst with an FeN5 active center (FePc-Py-CNT). Synchrotron X-ray absorption and Fourier transform infrared spectroscopy proved the presence of an Fe-N coordination bond between FePc and surface-bound pyridine. The resulting hybrid exhibited notably enhanced electrocatalytic NRR performance compared to FePc immobilized on CNTs based on pi-pi stacking interactions (FePc-CNT), resulting in doubled NH3 yield (21.7 mu g 1 h mgcat-1h-1) and Faradaic efficiency (22.2%). Theoretical calculations revealed that the axial coordination on FePc resulted in partial electron transfer from iron to pyridine, which efficiently suppresses the adsorption of H+ and improves the chemisorption of N2 at Fe sites. Meanwhile, the interfacial electron transfer was facilitated by pyridine as an electron transfer relay between FePc and CNTs. This work provides a unique strategy for the design of highly efficient NRR electrocatalysts at the molecular level.
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| 4. |
- Yang, Hao, et al.
(författare)
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Monolithic FAPbBr3 Photoanode for Photoelectrochemical Water Oxidation with Ultralow-Onset-Potential
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Despite considerable research efforts on photoelectrochemical (PEC) water splitting over the past few decades, its practical application is still impeded by the lack of efficient, stable, and scalable photoelectrodes. Herein, we demonstrate the facile fabrication of a metal-halide perovskite-based photoanode for PEC water oxidation. A hole transport material-free and precious metal-free FAPbBr3 photovoltaic (PV) device is fabricated for the first time to examine the charge separation performance of the FAPbBr3 absorber. With a planar structure using mesoporous carbon as a hole-conducting layer, the device achieved a solar-to-electrical power conversion efficiency of 9.2% and a Voc of 1.4 V. The solar cell architecture is successfully applied to build a monolithic photoanode with the FAPbBr3 absorber, carbon/graphite conductive protection layer, and NiFe catalyst layers for direct photo-driven water oxidation. With suitable energy band alignment and minimal contact loss, the photoanode delivers an ultralow onset potential below 0 V versus a reversible hydrogen electrode and a high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under constant solar illumination is successfully reached by the application of UV filter protection. A detailed photothermal investigation confirms that the photothermal effect can improve the overall performance of the perovskite photoanode. The results in this report are of great significance in guiding the further development of PV material-based photoelectrodes for solar fuel applications.
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| 5. |
- Yang, Hao, et al.
(författare)
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Monolithic FAPbBr3 photoanode for photoelectrochemical water oxidation with low onset-potential and enhanced stability
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Despite considerable research efforts on photoelectrochemical water splitting over the past decades, practical application faces challenges by the absence of efficient, stable, and scalable photoelectrodes. Herein, we report a metal-halide perovskite-based photoanode for photoelectrochemical water oxidation. With a planar structure using mesoporous carbon as a hole-conducting layer, the precious metal-free FAPbBr3 photovoltaic device achieves 9.2% solar-to-electrical power conversion efficiency and 1.4 V open-circuit voltage. The photovoltaic architecture successfully applies to build a monolithic photoanode with the FAPbBr3 absorber, carbon/graphite conductive protection layers, and NiFe catalyst layers for water oxidation. The photoanode delivers ultralow onset potential below 0 V versus the reversible hydrogen electrode and high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under solar illumination by applying ultraviolet-filter protection. The photothermal investigation verifies the performance boost in perovskite photoanode by photothermal effect. This study is significant in guiding the development of photovoltaic material-based photoelectrodes for solar fuel applications.
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| 6. |
- Zhao, Yilong, et al.
(författare)
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Efficient urea electrosynthesis from carbon dioxide and nitrate via alternating Cu–W bimetallic C–N coupling sites
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Electrocatalytic urea synthesis is an emerging alternative technology to the traditional energy-intensive industrial urea synthesis protocol. Novel strategies are urgently needed to promote the electrocatalytic C–N coupling process and inhibit the side reactions. Here, we report a CuWO4 catalyst with native bimetallic sites that achieves a high urea production rate (98.5 ± 3.2 μg h−1 mg−1cat) for the co-reduction of CO2 and NO3− with a high Faradaic efficiency (70.1 ± 2.4%) at −0.2 V versus the reversible hydrogen electrode. Mechanistic studies demonstrated that the combination of stable intermediates of *NO2 and *CO increases the probability of C–N coupling and reduces the potential barrier, resulting in high Faradaic efficiency and low overpotential. This study provides a new perspective on achieving efficient urea electrosynthesis by stabilizing the key reaction intermediates, which may guide the design of other electrochemical systems for high-value C–N bond-containing chemicals.
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| 7. |
- Zhou, Dinghua, et al.
(författare)
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WO3 Nanosheet-Supported IrW Alloy for High-Performance Acidic Overall Water Splitting with Low Ir Loading
- 2022
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:1, s. 970-980
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Tidskriftsartikel (refereegranskat)abstract
- Precious metals (like Ir, Ru, and Pt) and their derivatives are the benchmark catalysts for water splitting in acidic media due to their high stability and activity. However, the high cost and scarcity of these materials hamper the large-scale applications. To solve this issue, construction of catalysts containing low content of precious metals with high intrinsic activity can be an efficient strategy, which expectedly can decrease the cost but meanwhile preserve the activity. Herein, we synthesized an IrW/WO3 array catalyst by in situ formation of IrW alloy on hierarchical WO3 nanosheet arrays. With extremely low Ir content of 1.25 wt % in 0.5 M H2SO4, this composite catalyst not only shows superior water oxidation activity (the overpotential at 10 mA cm-2 is only 229 mV, significantly lower than that of the commercial IrO2 (358 mV)) but also exhibits excellent proton reduction performance (the overpotential at -10 mA cm-2 is 49 mV, close to that of commercial Pt/C catalyst (42 mV)), showing promising bifunctionality for the overall water splitting. As a result, only 1.5 V is needed to drive the overall water splitting at 10 mA cm-2 with a good long-term stability under acidic conditions. These remarkable features can be ascribed to the abundant active sites exposed by the three-dimensional nanostructure, and the high intrinsic activity per Ir site. The theoretical calculation verifies that Ir sites in IrW surface after oxidation have a higher intrinsic activity than IrO2 for water oxidation. We believe this research can supply a strategy to design highly active and stable catalysts with low loading of noble metals for acidic water splitting.
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