Ji Hyun Jang

NiO nanostructures with three distinct morphologies were fabricated by a sol-gel method and their morphology-dependent supercapacitor properties were exploited. The nanoflower- shaped NiO with a distinctive three-dimensional (3D) network and the highest pore volume shows the best supercapacitor properties. The nanopores in flower-shaped nanostructures, offering advantages in contact with and transport of the electrolyte, allow for 3D nanochannels in NiO structure, providing longer electron pathw

A mass-producible mesoporous graphene nanoball (MGB) was fabricated via a precursor-assisted chemical vapor deposition (CVD) technique for supercapacitor application. Polystyrene balls and reduced iron created under high temperature and a hydrogen gas environment provide a solid carbon source and a catalyst for graphene growth during the precursor-assisted CVD process, respectively. Carboxylic acid and sulfonic acid functionalization of the polystyrene ball facilitates homogeneous dispersion of

Abstract Despite their safety, nontoxicity, and cost‐effectiveness, zinc aqueous batteries still suffer from limited rechargeability and poor cycle life, largely due to spontaneous surface corrosion and formation of large Zn dendrites by irregular and uneven plating and stripping. In this work, these untoward effects are minimized by covering Zn electrodes with ultrathin layers of covalent organic frameworks, COFs. These nanoporous and mechanically flexible films form by self‐assembly—via the st

Solar desalination via thermal evaporation of seawater is one of the most promising technologies for addressing the serious problem of global water scarcity because it does not require additional supporting energy other than infinite solar energy for generating clean water. However, low efficiency and a large amount of heat loss are considered critical limitations of solar desalination technology. The combination of mesoporous three-dimensional graphene networks (3DGNs) with a high solar absorpt

Abstract To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoele

Abstract Utilizing the broad‐band solar spectrum for sea water desalination is a promising method that can provide fresh water without sophisticated infrastructures. However, the solar‐to‐vapour efficiency has been limited due to the lack of a proper design for the evaporator to deal with either a large amount of heat loss or salt accumulation. Here, these issues are addressed via two cost‐effective approaches: I) a rational design of a concave shaped supporter by 3D‐printing that can promote th

We report a robust and direct route to fabricate a three-dimensional nano-foam of few-layer graphene (3D-NFG) with large area coverage via a chemical vapor deposition (CVD) technique. Pyrolysis of polymer/nickel precursor film under a hydrogen environment, simply prepared by spin-coating, leads to the creation of nano-foam in the film and the reduction process of nickel ions. Carbonized-C and the nickel nano-frame formed from the pyrolysis are used as a solid carbon source and as a catalyst for

We report a fully reversible and robust shape-memory effect in a two-dimensional nanoscale periodic structure composed of three steps, the elastic instability governing the transformation, the plasticity that locks in the transformed pattern as a result of an increase in glass transition temperature (T(g)), and the subsequent elastic recovery due to the vapor-induced decrease in T(g). Solvent swelling of a cross-linked epoxy/air cylinder structure induces an elastic instability that causes a rev

A highly-porous, binder free 3D-NiCo₂O₄/Ni nanostructure on the Ni-wire was fabricated for flexible fiber supercapacitors. The fabricated device exhibited enhanced capacitance, high efficiency, good cycling stability, and flexibility.

This study introduces an in situ fabrication of nanoporous hematite with a Ti-doped SiOx passivation layer for a high-performance water-splitting system. The nanoporous hematite with a Ti-doped SiOx layer (Ti-(SiOx /np-Fe2 O3 )) has a photocurrent density of 2.44 mA cm(-2) at 1.23 VRHE and 3.70 mA cm(-2) at 1.50 VRHE . When a cobalt phosphate co-catalyst was applied to Ti-(SiOx /np-Fe2 O3 ), the photocurrent density reached 3.19 mA cm(-2) at 1.23 VRHE with stability, which shows great potential

In this report, we show that by creating a nanoporous haematite (α-Fe2O3) structure using boric acid (H3BO3) treatment, the chronic issue of the short diffusion length of carriers in α-Fe2O3 for photoelectrochemical (PEC) applications can be successfully addressed. The slow release of Fe3+ ions because of the presence of H3BO3 leads to the creation of smaller dimension FeOOH nanorods, creating nanoporous α-Fe2O3 nanorods, composed of ∼15 nm α-Fe2O3 domains. The nanoporous α-Fe2O3 suppresses reco

We report that metal ions (M: Sn4+ and Ti4+) and boron-codoped hematite photoanodes with an n–n+ homojunction showed significantly increased photoelectrochemical (PEC) water splitting activity with greatly reduced surface recombination. The secondary B-doping of broadly used M-doped hematite photoanodes not only suppresses the number of M+ ions, which inevitably cause electron–hole pair (EHP) recombination, but also generates an internal electric field for easy hole extraction. Taking advantage

We present a simple route towards a superhydrophobic graphene surface, which opens up possibilities for transparent flexible graphene-based electrodes with a non-wetting property. By tailoring the surface energy and surface roughness, superhydrophobic properties of graphene with a contact angle greater than 150° at an optical transparency of 72.7% were obtained.