Bio-synthesis of finely distributed Ag nanoparticle-decorated TiO2 nanorods for sunlight-induced photoelectrochemical water splitting

Nano-Ag: Environmental applications and perspectives

Silver nanoparticles (AgNPs) are promising bactericidal agents and plasmonic NPs for environmental applications, owing to their various favorable properties. For example, AgNPs enables reactive oxygen species (ROS) generation, surface plasmon resonance (SPR), and specific reaction selectivities. In fact, AgNPs-based materials and their antimicrobial, optical, and electrical effects are at the forefront of nanotechnology, having applications in environmental disinfection, elimination of environmental pollutants, environmental detection, and energy conversions. This review aims to comprehensively summarize the advanced applications and fundamental mechanisms to provide the guidelines for future work in the field of AgNPs implanted functional materials. The state-of-art terms including (photo)(electro)catalytic reactions, heterojunction formation, the generation and attacking of ROS, genetic damage, hot electron generation and transfer, localized surface plasmon resonance (LSPR), plasmon resonance energy transfer (PERT), near field electromagnetic enhancement, structure-function relationship, and reaction selectivities have been covered in this review. It is expected that this review may provide insights into the rational development in the next generation of AgNPs-based nanomaterials with excellent performances.

Three-dimensional core-shell heterostructure of tungsten trioxide/bismuth molybdate/cobalt phosphate for enhanced photoelectrochemical water splitting

Hydrogen has attracted increasing attention as clean energy for fuel cells over the past decade. Photoelectrochemical (PEC) water splitting is considered the most feasible production method but its practical efficiency depends significantly on the photogeneration rate of electron (e^-) and hole (h⁺) on a semiconductor photoanode and the rapid separation of these charge carriers. A proper match of small and large bandgap positions is also necessary. This paper presents a three-dimensional core-shell heterostructured tungsten trioxide/bismuth molybdate/cobalt phosphate (WO₃/Bi₂MoO₆/Co-Pi) photocatalyst synthesized using simultaneous hydrothermal and electrodeposition techniques. Uniform Bi₂MoO₆ nanoflakes formed on WO₃ nanoplates as evidenced by various micro-spectroscopic techniques. The as-prepared WO₃/Bi₂MoO₆/Co-Pi hetero-photocatalyst exhibited significantly high photoelectrochemical activity, where its photocurrent efficiency was 4.6 times greater than that of the constituent WO_3. Such drastic improvement in the PEC properties can be corroborated by the appropriate bandgap alignment among WO₃, Bi₂MoO₆, and Co-Pi, resulting in a sufficient charge carrier density with efficient, fast charge-transport complementing their structural-morphological synergy. Furthermore, a heterojunction charge-transfer mechanism was proposed to verify the role of the co-catalyst, Co-Pi, in enhancing the photocurrent at the WO₃/Bi₂MoO₆ photoanode under the same applied bias.

TiO2 as a Photocatalyst for Water Splitting-An Experimental and Theoretical Review

Hydrogen produced from water using photocatalysts driven by sunlight is a sustainable way to overcome the intermittency issues of solar power and provide a green alternative to fossil fuels. TiO₂ has been used as a photocatalyst since the 1970s due to its low cost, earth abundance, and stability. There has been a wide range of research activities in order to enhance the use of TiO₂ as a photocatalyst using dopants, modifying the surface, or depositing noble metals. However, the issues such as wide bandgap, high electron-hole recombination time, and a large overpotential for the hydrogen evolution reaction (HER) persist as a challenge. Here, we review state-of-the-art experimental and theoretical research on TiO₂ based photocatalysts and identify challenges that have to be focused on to drive the field further. We conclude with a discussion of four challenges for TiO₂ photocatalysts-non-standardized presentation of results, bandgap in the ultraviolet (UV) region, lack of collaboration between experimental and theoretical work, and lack of large/small scale production facilities. We also highlight the importance of combining computational modeling with experimental work to make further advances in this exciting field.