摘要 : Surface engineering of active materials to generate desired energy state is critical to fabricate high-performance heterogeneous catalysts. However, its realization in a controllable level remains challenging. Using oxygen evolution reaction (OER) as a model reaction, we report a surface-mediated Fe deposition strategy to electronically tailor surface energy states of porous Co 3 O 4 (Fe-pCo 3 O 4 ) for enhanced activity towards OER. The Fe-pCo 3 O 4 exhibits a low overpotential of 280 mV to reach an OER current density of 100 mA cm −2, and a fast-kinetic behavior with a low Tafel slop of 58.2 mV dec −1, outperforming Co 3 O 4 -based OER catalysts recently reported and also the noble IrO 2 . The engineered material retains 100% of its original activity after operating at an overpotential of 350 mV for 100 h. A combination of theoretical calculations and experimental results finds out that the surface doped Fe promotes a high energy state and desired coordination environment in the near surface region, which enables optimized OER intermediates binding and favorably changes the rate-determining step.

摘要 : Poly(3,4-ethylenedioxythiophene) (PEDOT)-based hydrogel has been studied extensively due to its low cost, good chemical/mechanical stability, printability and high biocompatibility, but still suffers from its relatively low conductivity and complex synthesis method. In this work, we use vanadium pentoxide (V2O5) flat-nanofiber networked thin layer-structure to boost EDOT-intercalation reaction for rapidly producing fiber-reinforced conductive gel (FCG), achieving superior conductivity of 10 S cm-1 and extremely fast production time (10 s). The superior FCG formation mechanism is ascribed to the V2O5 flat-nanofiber networked thin layer-structure allowing EDOT rapidly penetrating to inter-layers and replacing inside water molecules for polymerization to high-conductive FCG. The FCG can be used to print various patterns and are further used to fabricate a flexible biomimetic hydrogen peroxide (H2O2) sensor, delivering a high sensitivity of 2100 µA mM-1 cm-2, ranking the best among all flexible enzyme-free H2O2 sensors. More importantly, this flexible biomimetic H2O2 sensor is successfully applied to real-time detect living cells-secreted H2O2, demonstrating its application for in situ monitoring of small biomolecules released from living cells. This work offers a universal approach to synthesize high-conductive printable hydrogels by designing precursors meriting from both physics and chemistry, while holding great promise for mass-manufacturing inexpensive hydrogels in applications of sensing or wearable devices.

摘要 : Pore structure plays critical roles in electrode kinetics but very challenging to tailor porous nanowires with rationally distributed pore sizes in a bioelectrochemical system. Herein a hierarchically porous nanowires-material is delicately tuned for an optimal pore structure by adjusting the weight percentage of SiO2-hard template in an electrospinning precursor solution. The as-prepared optimal electrospinning nanowires further used as an anode of microbial fuel cells (MFCs), delivering a maximum output power density of 1, 407.42 mW·m−2 with 4.24 and 10 times higher than that of the non-porous fiber and carbon cloth anode, respectively. The great enhancement is attributed to the rational pore structure which offers the largest surface area while the rich-mesopores well match with the size of electron mediators for a high density of catalytic centers. This work provides thoughtful insights to design of hierarchical porous electrode for high-performance MFCs and other bioelectrochemical system devices.

摘要 : It is a great challenge to detect superoxide anions (O2•–) with low level concentrations and short half-life in biological systems. Herein, mild and facile Mn etching for zeolitic imidazolate framework-67 (ZIF-67) was used to synthesize Mn/ZIF-67 with a hydrangea-like nanostructure for biomimetic sensing of O2•– released from living cells. The tailored optimal Mn/ZIF-67 sensor achieves a high selectivity, a fast response time (1.6 s), a broad linear detection range (1.5 nM–10 μM), an ultralow detection limit (0.8 nM), and a remarkably high sensitivity (439.2 μA μM–1 cm–2) that ranks the best among all reported conventional Mn- and Co-compound-based nanozymes such as Co2P and Mn3(PO4)2. The excellent sensing performances are attributed to the Mn etching-generating hydrangea-like nanostructure for a significantly increased reaction surface area and coordinating Mn2+ with Co2+ to raise the oxidation state of Co2+ for fast electron transfer during the oxidation of O2•–. This work holds great potential for a highly sensitive O2•– nanozyme sensor in practical clinical diagnosis and bioscience research, while shedding fundamental light on designs of sensitive nanozyme sensors by incorporating two metal ions with largely different negativity for an efficient electrocatalytic process, thereby possessing universal significance.

摘要 : The sluggish water oxidation process is a severe obstacle for solar-driven water splitting. Therefore, it is imperative to develop a suitable photocatalyst with reduced energy barrier for strong oxidation. In this study, a Z-scheme BiVO4/NiCo2O4 (BVO/NCO) heterojunction system was designed by decorating ultrathin nickel-cobalt (NiCo2O4) spinel nanosheets on BiVO4 as an efficient photocatalyst for water oxidation. The unique structure of the system significantly reduced the energy barrier and improved the oxidation ability of BiVO4 to efficiently enhance the separation and transfer of the photogenerated carriers. Thus, the photocatalyst delivered an excellent O2 evolution performance of 1640.9 μmol∙g-1∙h-1 and showed 124% improved efficiency as compared to pristine BiVO4 and a quantum efficiency of 5.39% at 400 nm for O2 evolution. Additionally, the theoretical calculations revealed that the formation of *OOH was the rate-determining step for water oxidation. The decoration with NiCo2O4 significantly reduced the energy barrier between *O and *OOH, which eventually improved the photocatalytic performance of BVO/NCO. The results hold great promise for the potential application of spinel-based materials in efficient photocatalytic O2 evolution and offer fundamental insights into the design of efficient water oxidation heterojunctions.

摘要 : Electrochemical nitrate reduction to ammonia (NRA) has attracted increasing attention recently, as it can not only eliminate the harmful nitrate in water, but also produce high value-added ammonia in ambient conditions. Noble metals such as Ru, Pd, Pt, etc., show good activity for NRA but the high price and scarcity restrict their practical applications. Therefore, to develop efficient non-noble metal-based catalysts towards NRA is of great significance. In this contribution, CoFe layered double hydroxide (CoFe LDH) is demonstrated as an efficient non-noble electrocatalyst for NRA. Specifically, NH 3 selectivity and Faradaic efficiency of CoFe LDH in alkaline conditions are up to 98.93% and 97.68%, respectively. CoFe LDH also maintains good operation durability during 12 consecutive recycling tests (36 h). It is found that there is strong electronic interaction between Co and Fe species, which accelerates reaction kinetics of CoFe LHD. Density functional theory calculations also suggest that CoFe LDH can favorably promote the adsorption of intermediates (NO 3 – and NO 2 – ) and desorption of NH 3, eventually achieving efficient and selective NH 3 production.

摘要 : Developing low-cost and high-performance electrocatalysts for electrochemical nitrate reduction to ammonia (NRA) is of great importance to alleviate increasingly energy demand and environmental pollution. Cu electrodes have been widely explored towards NRA, while high overpotential is always required and ammonia selectivity is relatively low. Herein, Ce-doping Cu electrode is designed and fabricated via electrochemical deposition strategy and its electrocatalytic NRA in alkaline conditions is investigated. Effect of the Ce content on the performance of the Ce-doped Cu electrodes are studied, showing that the Cu 10 Ce 10 demonstrates the best performance. It achieves a high ammonia yield rate of 0.99 mmol h −1 cm −2, Faradaic efficiency of 98.43%, nitrate conversion rate of 94% and NH 3 selectivity of 79.33%. It is found that Ce-doping Cu electrode could tune electronic structure of Cu by generating Cu/Cu 2 O interfacial structure as active phase, which reduces the overpotential of nitrate reduction and improves the NH 3 selectivity of Cu electrodes.

摘要 : All-organic lithium-ion battery (AOLB) is a new type of energy storage device that is sustainable, versatile and potentially low-cost. Current development of AOLBs is still largely restrained by the Li-contained organic cathodes, which should be air stable and high performance. In this work, lithium tetracyanoquinodimethan (LiTCNQ) is presented as a new Li-contained organic cathode for AOLBs. Theoretical calculation proves the air-stable nature of LiTCNQ, of which the frontline molecular orbital mismatches with O 2 molecules with an energy difference more than 6 eV. The LiTCNQ-based half-cells deliver an outstanding performance with an average redox potential of 3.2 V, a capacity of 127 mAh g −1 at a current density of 20 mA g −1, and a capacity retention of 85% after 100 cycles. Advanced characterizations prove the high reversibility of transformation between C N groups of TCNQ and -C=N groups of LiTCNQ. The LiTCNQ-based AOLBs with Li2TPh anode exhibit a high capacity of 150 mAh g −1 at a current density of 20 mA g −1, an energy density up to 270 wh kg −1, and a capacity retention of 70% after 50 cycles, making it feasible for LiTCNQ as an air-stable cathode material for high-performance AOLBs.

摘要 : The electrocatalytic reduction of nitrate to ammonia is of scientific and practical significance. The feasibility of using two-dimensional transition metal carbides, M3C2 MXenes, as an electrocatalyst for converting NO3− to NH3, is demonstrated by using density functional theory calculations. Reaction active center analysis reveals that the reaction prefers to occur on the basal plane rather than the edge plane. By systematically analyzing thermodynamic and kinetic aspects, the most probable reaction pathway was determined to be consecutive deoxygenation followed by hydrogenation: NO3− → NO3 → NO2 → NO → N → NH → NH2 → NH3 → NH3(g). Furthermore, it's found that the deoxygenation processes are exothermic while the hydrogenation processes are endothermic. Both catalytic deoxygenation and hydrogenation processes in NRA are substantially affected by pH. Thus, the rate-determining step and overpotential exhibit pH dependent characteristics. For unfunctionalized MXenes, the NRA is suppressed due to the strong hydrogen evolution reaction (HER). By functionalization, the NRA catalytic activity of Ti3C2 and transition metal doped Ti3C2 MXenes increases effectively. This improvement is attributed to the high oxidation states of Ti atoms at catalytic centers and weakening of NHx adsorption on the MXene surfaces, thereby facilitating easy hydrogenation. In particular, partially O-vacant Ti3C2O2 is recognized as one promising NRA electrocatalyst, with the free energy change of every reaction step being negative. The findings of this work provide new strategies for the rational design of MXene-based NRA electrocatalysts with universal significance.

摘要 : An effective combination of smart materials plays an important role in charge transfer and separation for high photoelectric conversion efficiency (PCE) and stable solar cells. Black phosphorus quantum dots (BPQDs) have been revealed as a direct band gap semiconductor with ultrahigh conductivity, which have been explored in the present work as an additive component to a precursor solution of SnO2 nanoparticles that can effectively improve the performance of SnO2 electron transport layer (ETL)-based perovskite solar cells. Such a device can yield a high PCE of 21% with the SnO2/BPQDs mixed ETL, which is higher than those of perovskite solar cells based on SnO2 single layer (18.2%), BPQDs/SnO2 bilayer (19.5%), and SnO2/BPQDs bilayer (20.5%) samples. The mixed samples still possess good stability of more than 90% efficiency after 1000 h under AM 1.5G lamp irradiation and negligible hysteresis. It is found that the strong interaction of BPQDs with SnO2 can not only modify the defects inherent to the SnO2 layer but also inhibit the oxidation of BPQDs. This work provides a promising functional material for SnO2 ETL-based perovskite solar cells and proves that the BPQD-based modification strategy is useful for designing other solar cells with high performance.