Zhongke Yuan

A general approach to cobalt-based homobimetallic phosphide ultrathin nanosheets for highly efficient oxygen evolution in alkaline media

A general and effective approach was proposed to fabricate a new family of Co-based bimetallic phosphide ultrathin nanosheets (CoM-P-NS, M = Ni, Mn, Cu, Zn) with homogeneous composition and unique porous architecture using ultrathin metal–organic framework nanosheets (MOFNs) as precursors for the first time, which yielded synergistically active sites, mass transport and dynamic modulations for the oxygen evolution reaction (OER). The optimized samples showed remarkable oxygen evolution activity in alkaline electrolytes, outperforming both the commercial RuO2 and Ir/C benchmarks and ranking the best among all the metal-phosphide electrocatalysts reported to date.

A General Electrode Design Strategy for Flexible Fiber Micro-Pseudocapacitors Combining Ultrahigh Energy and Power Delivery

Herein, a general strategy is proposed to boost the energy storage capability of pseudocapacitive materials (i.e., MnO2) to their theoretical limits in unconventional 1D fiber configuration by rationally designing bicontinuous porous Ni skeleton@metal wire “sheath–core” metallic scaffold as a versatile host. As a proof of concept, the 1D metallic scaffold supported‐MnO2 fiber electrode is demonstrated. The proposed “sheath” design not only affords large electrode surface area with ordered macropores for large electrolyte‐ion accessibility and high electroactive material loading, but also renders interconnected porous metallic skeleton for efficient electronic and ionic transport, while the metallic “core” functions as an extra current collector to promote long‐distance electron transport and electron collection. Benefiting from all these merits, the optimized fiber electrode yields unprecedented specific areal capacitance of 1303.6 mF cm−2 (1278 F g−1 based on MnO2, approaching the theoretical value of 1370 F g−1) in liquid KOH and 847.22 mF cm−2 in polyvinyl alcohol (PVA)/KOH gel electrolyte, 2–350 times of previously reported fiber electrodes. The solid‐state fiber micro‐pseudocapacitors simultaneously achieve remarkable areal energy and power densities of 18.83 µWh cm−2 and 16.33 mW cm−2, greatly exceeding the existing symmetric fiber supercapacitors, together with long cycle life and high rate capability.

One-Pot Large-Scale Synthesis of Carbon Quantum Dots: Efficient Cathode Interlayers for Polymer Solar Cells

Cathode interlayers (CILs) with low-cost, low-toxicity, and excellent cathode modification ability are necessary for the large-scale industrialization of polymer solar cells (PSCs). In this contribution, we demonstrated one-pot synthesized carbon quantum dots (C-dots) with high production to serve as efficient CIL for inverted PSCs. The C-dots were synthesized by a facile, economical microwave pyrolysis in a household microwave oven within 7 min. Ultraviolet photoelectron spectroscopy (UPS) studies showed that the C-dots possessed the ability to form a dipole at the interface, resulting in the decrease of the work function (WF) of cathode. External quantum efficiency (EQE) measurements and 2D excitation-emission topographical maps revealed that the C-dots down-shifted the high energy near-ultraviolet light to low energy visible light to generate more photocurrent. Remarkably improvement of power conversion efficiency (PCE) was attained by incorporation of C-dots as CIL. The PCE was boosted up from 4.14% to 8.13% with C-dots as CIL, which is one of the best efficiency for i-PSCs used carbon based materials as interlayers. These results demonstrated that C-dots can be a potential candidate for future low cost and large area PSCs producing.

Integrative solar absorbers for highly efficient solar steam generation

Herein, carbonized melamine foams obtained through one-step calcination were first used as integrative solar absorbers (ISAs) for water evaporation, realizing highly efficient solar steam generation. The optimized ISA shows excellent light absorption (>96%) for solar energy due to the features of high porosity, lightweight, mechanical robustness inherited from melamine foams, as well as low thermal conductivities attributed to the appropriate pore scale and high nitrogen content, beneficial for the decrease of thermal diffusions. As a result, compared with the former reports, the optimized ISA reported herein exhibits one of the best performances for solar steam generation with a water evaporation rate of 1.270 kg m−2 h−1 and an energy conversion efficiency of 87.3% under 1 kW m−2 solar illumination and realizes effective solar desalinations. In addition, the ISAs can work out efficient water evaporation under a high humidity of 90%. Due to their simple preparation, recyclability, and aforementioned extraordinary performance, the ISAs can be expected to be potential solar absorbers for commercial, renewable, and portable solar steam generations.

Self-Assembled Graphene-Based Architectures and Their Applications

Abstract Due to unique planar structures and remarkable thermal, electronic, and mechanical properties, chemically modified graphenes (CMGs) such as graphene oxides, reduced graphene oxides, and the related derivatives are recognized as the attractive building blocks for “bottom‐up” nanotechnology, while self‐assembly of CMGs has emerged as one of the most promising approaches to construct advanced functional materials/systems based on graphene. By virtue of a variety of noncovalent forces like hydrogen bonding, van der Waals interaction, metal‐to‐ligand bonds, electrostatic attraction, hydrophobic–hydrophilic interactions, and π–π interactions, the CMGs bearing various functional groups are highly desirable for the assemblies with themselves and a variety of organic and/or inorganic species which can yield various hierarchical nanostructures and macroscopic composites endowed with unique structures, properties, and functions for widespread technological applications such as electronics, optoelectronics, electrocatalysis/photocatalysis, environment, and energy storage and conversion. In this review, significant recent advances concerning the self‐assembly of CMGs are summarized, and the broad applications of self‐assembled graphene‐based materials as well as some future opportunities and challenges in this vibrant area are elucidated.

Connection between the conformation and emission properties of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] single molecules during thermal annealing

We investigated the transitions of conformations and their effects on emission properties of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) single molecules in PMMA matrix during thermal annealing process. Total internal reflection fluorescence microscopy measurements reveal the transformation from collapsed conformations to extended, highly ordered rod-like structures of MEH-PPV single molecules during thermal annealing. The blue shifts in the ensemble single molecule PL spectra support our hypnosis. The transition occurs as the annealing temperature exceeds 100 °C, implying that an annealing temperature near the glass transition temperature Tg of matrix is ideal for the control and optimization of blend polymer films.

Boosting water oxidation on metal-free carbon nanotubes via directional interfacial charge-transfer induced by an adsorbed polyelectrolyte

Engineering the surface and electronic structures of nanocarbons is a viable strategy to boost their catalytic performance. Herein, rather than conventional covalent doping, we used the concept of interfacial charge transfer doping of carbon nanotubes (CNTs) to noncovalently adsorb certain polyelectrolytes (i.e. poly(diallyldimethylammonium chloride), PDDA, acceptor) onto pure CNTs (donor) to act as a buffer layer for richening reactants (OH−) via electrostatic interaction and to induce notable interfacial charge redistribution via directional intermolecular charge-transfer, which not only improves the reaction kinetics but also creates a high density of catalytic carbon sites, eventually transforming the inactive CNTs into efficient metal-free water oxidation catalysts. As expected, the resulting PDDA-adsorbed CNT catalysts yielded a remarkably lower overpotential of 370 mV at 10.0 mA cm−2 with a smaller Tafel slope of 76 mV dec−1 with respect to pure CNTs (>520 mV, 166 mV dec−1), even on a par with the benchmark RuO2 (360 mV, 137 mV dec−1) in 0.1 M KOH.

In Situ Activating Strategy to Significantly Boost Oxygen Electrocatalysis of Commercial Carbon Cloth for Flexible and Rechargeable Zn-Air Batteries

Abstract An in situ strategy to simultaneously boost oxygen reduction and oxygen evolution (ORR/OER) activities of commercial carbon textiles is reported and the direct use of such ubiquitous raw material as low‐cost, efficient, robust, self‐supporting, and bifunctional air electrodes in rechargeable Zn‐air batteries is demonstrated. This strategy not only furnishes carbon textiles with a large surface area and hierarchical meso‐microporosity, but also enables efficient dual‐doping of N and S into carbon skeletons while retaining high conductivity and stable monolithic structures. Thus, although original carbon textile has rather poor catalytic activity, the activated textiles without loading other active materials yield effective ORR/OER bifunctionality and stability with a much lower reversible overpotential (0.87 V) than those of Pt/C (1.10 V) and RuO2 (1.02 V) and many reported metal‐free bifunctional catalysts. Importantly, they can concurrently function as current collectors and as ORR/OER catalysts for rechargeable aqueous and flexible solid‐state Zn‐air batteries, showing excellent cell performance, long lifetime, and high flexibility.