Xiaozhen Hu

Tailoring Graphene Oxide‐Based Aerogels for Efficient Solar Steam Generation under One Sun

Graphene oxide-based aerogels with carefully tailored properties are developed to enable efficient solar steam generation. Aerogels, with inherent porous structures, are excellent thermal insulators and provide channels for water supply and vapor escape. With enhanced absorption and hydrophilicity by incorporation of carbon nanotubes and sodium alginate, the resulting aerogels can enable efficient (≈83%) solar steam generation under one-sun illumination.

Mushrooms as Efficient Solar Steam-Generation Devices

Solar steam generation is emerging as a promising technology, for its potential in harvesting solar energy for various applications such as desalination and sterilization. Recent studies have reported a variety of artificial structures that are designed and fabricated to improve energy conversion efficiencies by enhancing solar absorption, heat localization, water supply, and vapor transportation. Mushrooms, as a kind of living organism, are surprisingly found to be efficient solar steam-generation devices for the first time. Natural and carbonized mushrooms can achieve ≈62% and ≈78% conversion efficiencies under 1 sun illumination, respectively. It is found that this capability of high solar steam generation is attributed to the unique natural structure of mushroom, umbrella-shaped black pileus, porous context, and fibrous stipe with a small cross section. These features not only provide efficient light absorption, water supply, and vapor escape, but also suppress three components of heat losses at the same time. These findings not only reveal the hidden talent of mushrooms as low-cost materials for solar steam generation, but also provide inspiration for the future development of high-performance solar thermal conversion devices.

Poly(dimethylsiloxane) Thin Film as a Stable Interfacial Layer for High-Performance Lithium-Metal Battery Anodes

A modified poly(dimethylsiloxane) film with nanopores, fabricated through a scalable and low-cost process, can serve as a protective layer for improving lithium-metal anodes. This film can suppress Li-dendrite formation because of its chemical inertness and mechanical properties. Stable cycling over 200 cycles with an averaged CE of 94.5% is demonstrated at 0.5 mA cm-2 .

Simultaneous Purification and Perforation of Low-Grade Si Sources for Lithium-Ion Battery Anode

Silicon is regarded as one of the most promising candidates for lithium-ion battery anodes because of its abundance and high theoretical capacity. Various silicon nanostructures have been heavily investigated to improve electrochemical performance by addressing issues related to structure fracture and unstable solid-electrolyte interphase (SEI). However, to further enable widespread applications, scalable and cost-effective processes need to be developed to produce these nanostructures at large quantity with finely controlled structures and morphologies. In this study, we develop a scalable and low cost process to produce porous silicon directly from low grade silicon through ball-milling and modified metal-assisted chemical etching. The morphology of porous silicon can be drastically changed from porous-network to nanowire-array by adjusting the component in reaction solutions. Meanwhile, this perforation process can also effectively remove the impurities and, therefore, increase Si purity (up to 99.4%) significantly from low-grade and low-cost ferrosilicon (purity of 83.4%) sources. The electrochemical examinations indicate that these porous silicon structures with carbon treatment can deliver a stable capacity of 1287 mAh g(-1) over 100 cycles at a current density of 2 A g(-1). This type of purified porous silicon with finely controlled morphology, produced by a scalable and cost-effective fabrication process, can also serve as promising candidates for many other energy applications, such as thermoelectrics and solar energy conversion devices.

Tuning Transpiration by Interfacial Solar Absorber-Leaf Engineering

Abstract Plant transpiration, a process of water movement through a plant and its evaporation from aerial parts especially leaves, consumes a large component of the total continental precipitation (≈48%) and significantly influences global water distribution and climate. To date, various chemical and/or biological explorations have been made to tune the transpiration but with uncertain environmental risks. In recent years, interfacial solar steam/vapor generation is attracting a lot of attention for achieving high energy transfer efficiency. Various optical and thermal designs at the solar absorber–water interface for potential applications in water purification, seawater desalination, and power generation appear. In this work, the concept of interfacial solar vapor generation is extended to tunable plant transpiration by showing for the first time that the transpiration efficiency can also be enhanced or suppressed through engineering the solar absorber–leaf interface. By tuning the solar absorption of membrane in direct touch with green leaf, surface temperature of green leaf will change accordingly because of photothermal effect, thus the transpiration efficiency as well as temperature and relative humidity in the surrounding environment will be tuned. This tunable transpiration by interfacial absorber‐leaf engineering can open an alternative avenue to regulate local atmospheric temperature, humidity, and eventually hydrologic cycle.

Simultaneous Perforation and Doping of Si Nanoparticles for Lithium-Ion Battery Anode

Silicon nanostructures have served as promising building blocks for various applications, such as lithium-ion batteries, thermoelectrics, and solar energy conversions. Particularly, control of porosity and doping is critical for fine-tuning the mechanical, optical, and electrical properties of these silicon nanostructures. However, perforation and doping are usually separated processes, both of which are complicated and expensive. Here, we demonstrate that the porous nano-Si particles with controllable dopant can be massively produced through a facile and scalable method, combining ball-milling and acid-etching. Nano-Si with porosity as high as 45.8% can be achieved with 9 orders of magnitude of conductivity changes compared to intrinsic silicon. As an example for demonstration, the obtained nano-Si particles with 45.8% porosity and 3.7 atom % doping can serve as a promising anode for lithium-ion batteries with 2000 mA h/g retained over 100 cycles at the current density of 0.5 C, excellent rate performance with 1600 mA h/g at the current density of 5 C, and a stable cycling performance of above 1500 mA h/g retained over 940 cycles at the current density of 1 C with carbon coating.