Connor Kang Nuo Peh

Green chemistry synthesis of a nanocomposite graphene hydrogel with three-dimensional nano-mesopores for photocatalytic H2 production

In this work, we have developed a nanocomposite graphene hydrogel (NGH) based on green chemistry, employing vitamin C (VC) to attain a supramolecular 3D network of hybrid nanostructured materials. Here, it is shown that the hydrogel is an appropriate and robust host for stable a TiO2 semiconductor catalyst sensitized with visible light responsive nanostructured particles. The NGH is tailored with well-defined nano-mesopores, a large surface area, a highly dispersive nanosheet–nanorods–nanoparticle composite, and enhance visible light absorption. Finally, we demonstrate practical applications of utilizing the NGH with water containing pores for photocatalytic H2 production. An important pragmatic consideration of using a NGH is the ease of separation and recovery of the nanosized catalyst after the photoreaction which would otherwise require extensive and expensive nanofiltration.

Bifunctional 2D-on-2D MoO3 nanobelt/Ni(OH)2 nanosheets for supercapacitor-driven electrochromic energy storage

A hybrid composite that unifies multiple structural attributes is the key for improved functional device performance. Moreover, hierarchical and porous assembly of dissimilar constituent elements at various length scales and dimensionality is highly appropriate for mass transfer and surface/interfacial-dominated reactions. Here, we demonstrate solution processed 2D-on-2D hierarchical architecture of nanobelt core–nanosheets shell consisting of dissimilar transition metal composite. The defining benefits of such hetero-structured material design are short ion diffusion pathway of a thin 2D nanobelt core that is interfaced to large surface area and porous 2D nanosheets. Accordingly, an integrated energy system that delivers multiple functionalities, i.e. supercapacitive charge storage and electrochromic optical modulation, is investigated due to its attractive complementary energy storage and energy conservation capabilities. Consequently, bifunctional electrochromism–supercapacitive properties are demonstrated where desirable optical transmittance modulation and coloration efficiency properties in parallel with favorable pseudocapacitive storage and specific capacitance properties are simultaneously realized. Such an integrated energy system is anticipated to have a broad range of smart applications in buildings, automobiles and other emerging electronics needs.

Harvesting broadband absorption of the solar spectrum for enhanced photocatalytic H2 generation

Absorption of the solar spectrum in the visible and near infrared region is highly desirable to improve photocatalytic H2 generation. Traditionally, this can be fulfilled by designing photocatalyst materials with narrower band gaps, or with upconversion capabilities. However, such materials often pose challenges such as in synthesis, structural defects, and stability which may lead to adverse photocatalytic performance. This paper focuses on broadband utilization of the solar spectrum for enhanced photocatalysis solar H2 production where the spectrum not utilized by the photocatalysts is absorbed and converted to heat energy. This approach delves into harvesting the broadband spectrum for synergistic photocatalysis and thermal heat generation, with minimal photocatalyst material manipulation. The profound impact of temperature on photocatalysis was manifested in a drastic increase of H2 production by a maximum of 40-fold. The apparent quantum yield was also calculated to reach 66.9% using an ultraviolet LED light source. Outdoor testing verifies the potential of broad spectrum operation under natural sunlight as well as the convenience and simplicity of various reactor designs for practical photocatalysis applications.

Outside‐In Recrystallization of ZnS–Cu1.8S Hollow Spheres with Interdispersed Lattices for Enhanced Visible Light Solar Hydrogen Generation

For the first time an earth-abundant and nontoxic ZnS-Cu(1.8) S hybrid photocatalyst has been engineered with well-defined nanosheet hollow structures by a template-engaged method. In contrast to conventional surface coupling and loading, the unique outside-in recrystallization promotes co-precipitation of ZnS and Cu(1.8) S into homogeneous interdispersed lattices, hence forming a hybrid semiconductor with visible responsive photocatalytic activity. The as-derived ZnS-Cu(1.8) S semiconductor alloy is tailored into a hierarchical hollow structure to provide readily accessible porous shells and interior spaces for effective ion transfer/exchange. Notably, this synergistic morphology, interface and crystal lattice engineering, aim towards the design of novel nanocatalysts for various sustainable environmental and energy applications.

Solar-driven photothermal nanostructured materials designs and prerequisites for evaporation and catalysis applications

Solar energy is a major source of renewable energy with the potential to meet the energy demand and to support the sustainable development of the world. The efficient harvesting and conversion of solar energy is one of the key factors to maximize the utilization of solar energy. In general, solar energy can be harnessed and converted into various kinds of energy, including electricity, fuels and thermal energy, through photovoltaic, photochemical and photothermal processes, respectively. Among these technologies, photothermal conversion is a direct conversion process that has attained the highest achievable conversion efficiency. The photothermal effect has been used as a novel strategy to augment vaporization and catalysis performance. In this review, we look into the basis of the photothermal conversion process, the design of efficient photothermal conversion materials in terms of both light harvesting and thermal management, a fundamental understanding of various system schemes, and the recent progress in photothermal evaporation and catalysis applications. This review aims to afford researchers with a better understanding of the photothermal effect and provide a guide for the rational design and development of highly efficient photothermal materials in energy and environmental fields.

Plasmonic enhanced photoelectrochemical and photocatalytic performances of 1D coaxial Ag@Ag2S hybrids

Silver (Ag) as one of the most important plasmonic metals has attracted enormous attention due to its distinct surface plasmon resonance (SPR) absorption and high electrical conductivity. Here, we use Ag nanowires (NWs) as the starting material to prepare a series of core–shell structured Ag@Ag2S composites through an in situ controllable and spontaneous sulfidation process at room temperature. It has been found that the obtained coaxial Ag@Ag2S hybrid with an optimized ratio of Ag NWs exhibits enhanced photoelectrochemical and photocatalytic performances under visible light irradiation. The underlying contribution of Ag SPR to the enhancement of photoelectrochemical and photocatalytic activities of the Ag@Ag2S hybrids has been elucidated through wavelength-dependent experiments and transient absorption spectroscopy. The results indicate that the SPR phenomenon of Ag NWs has an influential effect on the photoelectrochemical and photocatalytic activities enhancement of Ag@Ag2S hybrids, which is often overlooked in the previous reports. An ultrafast electron transfer process (∼350 fs) from the Ag core to the Ag2S shell has been measured. This work provides a valuable insight into the role of the Ag component in improving the photoelectrochemical and photocatalytic performances of Ag–Ag2S hybrid nanosystems, which is expected to promote comprehensive understanding and better exploitation of plasmonic Ag in universal photophysical and photochemical systems.

Simultaneous in situ reduction and embedment of Cu nanoparticles into TiO2 for the design of exceptionally active and stable photocatalysts

Efficient charge separation for a photocatalyst can be realized via addition of a co-catalyst, whereby most conventional techniques, i.e., deposition–precipitation, photoreduction, hydrothermal and vapour phase deposition result typically in surface loading effects. Moreover, the loading amount is deliberately kept nominal (below 10 wt%) as excessive loading causes both agglomeration and light blocking issues which limit the performance and stability of the photocatalyst. This work demonstrates one-pot in situ synthesis towards interdispersion and inclusion of a high concentration (Cu : TiO2 weight ratio > 1) of a Cu NP co-catalyst into TiO2 nanosheets without compromising its critical dispersivity and light absorption properties. The exceptional photocatalytic H2 performance of 16.1 ± 0.35 mmol g−1 h−1 stems from the embedment and confinement of the small Cu NPs within the TiO2 matrix which facilitates a shorter diffusion distance, thereby increasing the number of electrons available for catalytic reactions. Thus, this work highlights a facile approach towards optimal interfacing of the hybrid catalyst constituents to mitigate the limited interfacial contact and charge transfer challenges commonly faced in photocatalyst design.

Solar absorber material and system designs for photothermal water vaporization towards clean water and energy production

Photothermal materials with broad solar absorption and high conversion efficiency have recently attracted significant interest. They are becoming a fast-growing research focus in the area of solar-driven vaporization for clean water production. The parallel development of thermal management strategies through both material and system designs has further improved the overall efficiency of solar vaporization. Collectively, this green solar-driven water vaporization technology has regained attention as a sustainable solution for water scarcity. In this review, we will report the recent progress in solar absorber material design based on various photothermal conversion mechanisms, evaluate the prerequisites in terms of optical, thermal and wetting properties for efficient solar-driven water vaporization, classify the systems based on different photothermal evaporation configurations and discuss other correlated applications in the areas of desalination, water purification and energy generation. This article aims to provide a comprehensive review on the current development in efficient photothermal evaporation, and suggest directions to further enhance its overall efficiency through the judicious choice of materials and system designs, while synchronously capitalizing waste energy to realize concurrent clean water and energy production.