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Research Article Issue
Organic ligand nanoarchitectonics for BiVO4 photoanodes surface passivation and cocatalyst grafting
Nano Research 2024, 17 (5): 3667-3674
Published: 11 November 2023
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Bismuth vanadate (BiVO4) is a promising photoanode material for efficient photoelectrochemical (PEC) water splitting, whereas its performance is inhibited by detrimental surface states. To solve the problem, herein, a low-cost organic molecule 1,3,5-benzenetricarboxylic acid (BTC) is selected for surface passivation of BiVO4 photoanodes (BVOs), which also provides bonding sites for Co2+ to anchor, resulting in a Co-BTC-BVO photoanode. Owing to its strong coordination with metal ions, BTC not only passivates surface states of BVO, but also provides bonding between BVO and catalytic active sites (Co2+) to form a molecular cocatalyst. Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer. The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) and a low onset potential of 0.22 VRHE under AM 1.5 G illumination, which ranks among the best photoanodes coupled with Co-based cocatalysts. This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.

Open Access Research Article Issue
Nitrogen incorporated oxygen vacancy enriched MnCo2Ox/BiVO4 photoanodes for efficient and stable photoelectrochemical water splitting
Nano Research 2024, 17 (3): 1140-1150
Published: 26 July 2023
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Oxygen vacancies in oxygen evolution cocatalysts (OECs) can significantly improve the photoelectrochemical (PEC) water splitting performance of photoanodes. However, OECs with abundant oxygen vacancies have a poor stability when exposing to the highly-oxidizing photogenerated holes. Herein, we partly fill oxygen vacancies in a MnCo2Ox OEC with N atoms by a combined electrodeposition and sol-gel method, which dramatically improves both photocurrent density and stability of a BiVO4 photoanode. The optimized N filled oxygen vacancy-rich MnCo2Ox/BiVO4 photoanode (3 at.% of N) exhibits an outstanding photocurrent density of 6.5 mA·cm−2 at 1.23 VRHE under AM 1.5 G illumination (100 mW·cm−2), and an excellent stability of over 150 h. Systematic characterizations and theoretical calculations demonstrate that N atoms stabilize the defect structure and modulate the surface electron distribution, which significantly enhances the stability and further increases the photocurrent density. Meanwhile, other heteroatoms such as carbon, phosphorus, and sulfur are confirmed to have similar effects on improving PEC water splitting performance of photoanodes.

Research Article Issue
Mesoporous MnO2 nanosheets for efficient electrocatalytic nitrogen reduction via high spin polarization induced by oxygen vacancy
Nano Research 2023, 16 (4): 4664-4670
Published: 24 October 2022
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The electrochemical N2 reduction reaction (NRR) represents a green and sustainable route for NH3 synthesis under ambient conditions. However, the mechanism of N2 activation in the electrocatalytic NRR remains unclear. Herein, we found that the high spin state Mn3+-Mn3+ pairs induced by oxygen vacancy in MnO2 nanosheets greatly enhance the catalytic activities. The strong electron transfer between d orbital of Mn and orbital of N2 forces the N2 to be of radical nature, which activates the hydrogenation process and weakens the N≡N bond. Based on the density functional theory (DFT) calculation results, we precisely designed mesoporous MnO2 nanosheets with rich oxygen vacancies via using methyltriphenylphosphonium bromide (MPB) to induce more Mn3+-Mn3+ pairs (Mn3-3-MnO2), which can achieve a fairly high ammonia yield of up to 147.2 µg·h−1·mgcat−1. at −0.75 V vs. reversible hydrogen electrode (RHE) and a high Faradaic efficiency (FE) of 11%. Furthermore, these mesoporous MnO2 nanosheets exhibit the superior durability with negligible changes in both NH3 yield and FE after a consecutive 6-recycle test and the current density electrolyzed over a 24-hour period. Our findings offer an approach to designing highly active transition metal catalysts for electrocatalytic nitrogen reduction.

Research Article Issue
Understanding the roles of carbon in carbon/g-C3N4 based photocatalysts for H2 evolution
Nano Research 2023, 16 (4): 4539-4545
Published: 15 October 2021
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Coupling graphitic carbon nitride (CN) with carbonaceous materials is an effective strategy to improve photocatalytic performance, but the contributions of carbonaceous materials are not fully understood. Herein, a new type of carbon/CN (CCN) complex photocatalyst is synthesized with a 6-fold enhancement of H2 evolution rate compared to that of pristine CN. The role of carbon in photocatalytic H2 evolution reaction is systemically studied and it is experimentally and theoretically revealed that carbon mainly contributes to the improved capability of exciton dissociation and enhanced electric conductivity for charge transfer, leading to an increased population of photo-carriers for photocatalytic reactions. Interestingly, the enhanced light absorption originated from carbon barely generates charge carriers for H2 evolution activity. These new findings will inspire the rational design of carbon-based photocatalysts for efficient solar fuel production.

Research Article Issue
Bridging localized electron states of pyrite-type CoS2 cocatalyst for activated solar H2 evolution
Nano Research 2022, 15 (1): 202-208
Published: 21 April 2021
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The development of low-cost and high-active cocatalysts is one of the most significant links for photocatalytic water splitting. Herein, a novel strategy of electron delocalization modulation for transition metal sulfides has been developed by anion hybridization. P-modified CoS2 (CoS2|P) nanocrystals were firstly fabricated via a gas-solid reaction and coupled with CdS nanorods to construct a composite catalyst for solar H2 evolution reaction (HER). The CdS/CoS2|P catalyst shows an HER rate of 57.8 μmol·h−1, which is 18 times that of the bare CdS, 8 times that of the CdS/CoS2, and twice that of Pt/CdS. The reduced energy barrier and suppressed reverse reaction for HER on the catalyst have been predicted and explained by density functional theory (DFT) calculation. The underlying design strategy of novel cocatalysts by electron delocalization modulation may shed light on the rational development of other advanced catalysts for energy conversion.

Research Article Issue
Enhanced CH4 selectivity in CO2 photocatalytic reduction over carbon quantum dots decorated and oxygen doping g-C3N4
Nano Research 2019, 12 (11): 2749-2759
Published: 23 September 2019
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Graphitic carbon nitride (g-C3N4, CN) exhibits inefficient charge separation, deficient CO2 adsorption and activation sites, and sluggish surface reaction kinetics, which have been recognized as the main barriers to its application in CO2 photocatalytic reduction. In this work, carbon quantum dot (CQD) decoration and oxygen atom doping were applied to CN by a facile one-step hydrothermal method. The incorporated CQDs not only facilitate charge transfer and separation, but also provide alternative CO2 adsorption and activation sites. Further, the oxygen-atom-doped CN (OCN), in which oxygen doping is accompanied by the formation of nitrogen defects, proves to be a sustainable H+ provider by facilitating the water dissociation and oxidation half-reactions. Because of the synergistic effect of the hybridized binary CQDs/OCN addressing the three challenging issues of the CN based materials, the performance of CO2 photocatalytic conversion to CH4 over CQDs/OCN-x (x represents the volume ratio of laboratory-used H2O2 (30 wt.%) in the mixed solution) is dramatically improved by 11 times at least. The hybrid photocatalyst design and mechanism proposed in this work could inspire more rational design and fabrication of effective photocatalysts for CO2 photocatalytic conversion with a high CH4 selectivity.

Research Article Issue
A new sodium iron phosphate as a stable high-rate cathode material for sodium ion batteries
Nano Research 2018, 11 (12): 6197-6205
Published: 12 July 2018
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Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications. However, due to the large size of Na+, most Na+ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation, resulting in unsatisfactory rate and cycling performances. Herein, we report a new type of sodium iron phosphate (Na0.71Fe1.07PO4), which exhibits an extremely small volume change (~ 1%) during desodiation. When applied as a cathode material for SIBs, this new phosphate delivers a capacity of 78 mA·h·g-1 even at a high rate of 50 C and maintains its capacity over 5, 000 cycles at 20 C. In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging. The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.

Research Article Issue
Construction of point-line-plane (0-1-2 dimensional) Fe2O3-SnO2/graphene hybrids as the anodes with excellent lithium storage capability
Nano Research 2017, 10 (1): 121-133
Published: 29 September 2016
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The assembly of hybrid nanomaterials has opened up a new direction for the construction of high-performance anodes for lithium-ion batteries (LIBs). In this work, we present a straightforward, eco-friendly, one-step hydrothermal protocol for the synthesis of a new type of Fe2O3-SnO2/graphene hybrid, in which zero-dimensional (0D) SnO2 nanoparticles with an average diameter of 8 nm and one-dimensional (1D) Fe2O3 nanorods with a length of ~150 nm are homogeneously attached onto two-dimensional (2D) reduced graphene oxide nanosheets, generating a unique point-line-plane (0D-1D-2D) architecture. The achieved Fe2O3-SnO2/graphene exhibits a well-defined morphology, a uniform size, and good monodispersity. As anode materials for LIBs, the hybrids exhibit a remarkable reversible capacity of 1, 530 mA·g−1 at a current density of 100 mA·g−1 after 200 cycles, as well as a high rate capability of 615 mAh·g−1 at 2, 000 mA·g−1. Detailed characterizations reveal that the superior lithium-storage capacity and good cycle stability of the hybrids arise from their peculiar hybrid nanostructure and conductive graphene matrix, as well as the synergistic interaction among the components.

Research Article Issue
Low-temperature processed solar cells with formamidinium tin halide perovskite/fullerene heterojunctions
Nano Research 2016, 9 (6): 1570-1577
Published: 29 March 2016
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A new type of lead-free, formamidinium (FA)-based halide perovskites, FASnI2Br, are investigated as light-harvesting materials for low-temperature processed p–i–n heterojunction solar cells with different configurations. The FASnI2Br perovskite, with a band-gap of 1.68 eV, exhibits optimal photovoltaic performance after low-temperature annealing at 75 ℃. By using C60 as electron-transport layer, the device yields a hysteresis-less power conversion efficiency of 1.72%. The possible use of an inorganic MoOx film as a new type of independent hole-transport layer for the present tin-based perovskite solar cells is also demonstrated.

Research Article Issue
Organic–inorganic bismuth (Ⅲ)-based material: A lead-free, air-stable and solution-processable light-absorber beyond organolead perovskites
Nano Research 2016, 9 (3): 692-702
Published: 09 January 2016
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Methylammonium bismuth (Ⅲ) iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic–inorganic bismuth-based material to replace lead/tin-based perovskite materials in solution-processable solar cells. The organic–inorganic bismuth-based material has advantages of non-toxicity, ambient stability, and low-temperature solution-processability, which provides a promising solution to address the toxicity and stability challenges in organolead- and organotin-based perovskite solar cells. We also demonstrated that trivalent metal cation-based organic–inorganic hybrid materials can exhibit photovoltaic effect, which may inspire more research work on developing and applying organic-inorganic hybrid materials beyond divalent metal cations (Pb (Ⅱ) and Sn (Ⅱ)) for solar energy applications.

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