Preparation of uniform gold nanoparticles of different quantity deposited on zinc oxide nanorods for photoelectrochemical water splitting

For the photocatalytic test, gold nanoparticles (AuNPs) were prepared using trisodium citrate dehydrate (TCD), following which they were combined on the surface of zinc oxide (ZnO) to prepare ZnO decorated with uniform AuNPs (ZnO/AuNP) photocatalysts. The photocatalytic performance with the ZnO/AuNP was estimated through the rhodamine B (RB) dye degradation under solar irradiation. ZnO/AuNP-30 showed the greatest photocatalytic performance, achieving dye degradation efficiency up to 78.65%. Photoelectrochemical (PEC) measurements were performed using the ZnO/AuNP photoanodes. With AuNP doping amounts of 10, 20, and 30 mL on the ZnO surface, photocurrent densities of 47.46, 63.74, and 68.64 mA cm^-2, respectively, were achieved at an applied voltage of 1.5 V. These values indicated that the doping of AuNPs on the ZnO surface is advantageous for enhancing its PEC water-splitting activity. The highest solar-to-hydrogen (STH) efficiency is 22% with the ZnO/AuNP-30 photoanode at an applied voltage of 0.88 V. The interfacial charge-transfer resistances at the interface were 40 and 2.2 kΩ cm² for the ZnO and ZnO/AuNP-30 photoanodes, respectively.

Synthesis and control strategies of nanomaterials for photoelectrochemical water splitting

Photoelectrochemical water splitting to produce hydrogen using solar energy can capture and directly convert solar energy into chemical energy, which is an effective way to deal with the current energy and environmental problems. The conversion efficiency of solar energy depends on the performance of semiconductor photoelectrodes in photoelectrochemical water splitting. This article presents our recent advances in the design and performance control of high-efficiency photoelectrocatalytic materials, followed by the discussion of the strategies employed for improving the performances of photoelectrodes in terms of photon absorption, charge separation and migration, as well as surface chemical reactions.

Solar light harvesting with multinary metal chalcogenide nanocrystals

The paper reviews the state of the art in the synthesis of multinary (ternary, quaternary and more complex) metal chalcogenide nanocrystals (NCs) and their applications as a light absorbing or an auxiliary component of light-harvesting systems. This includes solid-state and liquid-junction solar cells and photocatalytic/photoelectrochemical systems designed for the conversion of solar light into the electric current or the accumulation of solar energy in the form of products of various chemical reactions. The review discusses general aspects of the light absorption and photophysical properties of multinary metal chalcogenide NCs, the modern state of the synthetic strategies applied to produce the multinary metal chalcogenide NCs and related nanoheterostructures, and recent achievements in the metal chalcogenide NC-based solar cells and the photocatalytic/photoelectrochemical systems. The review is concluded by an outlook with a critical discussion of the most promising ways and challenging aspects of further progress in the metal chalcogenide NC-based solar photovoltaics and photochemistry.

Stability and Performance of Sulfide-, Nitride-, and Phosphide-Based Electrodes for Photocatalytic Solar Water Splitting

With the past decade of worldwide sustained efforts on artificial photosynthesis for photocatalytic solar water splitting and clean hydrogen generation by dedicated researchers and engineers from different disciplines, substantial progress has been achieved in raising its overall efficiency along with finding new photocatalysts. Various materials, systems, devices, and better fundamental understandings of the interplay between interfacial chemistry, electronic structure, and photogenerated charge dynamics involved have been developed. Nevertheless, the overall photocatalytic performance is yet to achieve its maximum theoretical limit. Moreover, the stability of well-known semiconductors (as well as novel ones) remains the biggest challenge that scientists are facing to develop durable industrial-scale devices for large-scale water oxidation and overall solar water splitting. In this Perspective, we summarize the major achievements and the different approaches carried out to improve the stability and performance of photoelectrodes based on sulfide, nitride, and phosphide semiconductors.

Enhanced photoelectrochemical water splitting by oxides heterojunction photocathode coupled with Ag

A novel one-dimensional Co₃O₄/CuO/Ag composite structure film was directly grown on indium tin oxide glass substrate by a simple hydrothermal method and electrodeposition method. The film was employed for the first time as a photocathode for photoelectrochemical (PEC) water splitting to generate hydrogen. The photocurrent density of the Co₃O₄/CuO/Ag composite structure achieved -5.13 mA cm^-2 at -0.2 V vs. RHE, which is roughly 12.8 times that of 1D Co₃O₄ nanowires and 3.31 times Co₃O₄/CuO heterojunction photocathodes. The enhanced PEC performance of this Co₃O₄/CuO/Ag composite structure ascribes increased light-harvesting and light-absorption, distensible photoresponse range, decreased interface charge transfer resistance, and improved photogenerated electron-hole pairs transfer and separation.

Compound Copper Chalcogenide Nanocrystals

This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), energy storage (lithium-ion batteries, hydrogen generation), emissive materials (plasmonics, LEDs, biolabelling), sensors (electrochemical, biochemical), biomedical devices (magnetic resonance imaging, X-ray computer tomography), and medical therapies (photochemothermal therapies, immunotherapy, radiotherapy, and drug delivery). The confluence of advances in the synthesis, assembly, and application of these NCs in the past decade has the potential to significantly impact society, both economically and environmentally.

Strain-induced structural defects and their effects on the electrochemical performances of silicon core/germanium shell nanowire heterostructures

We report on strain-induced structural defect formation in core Si nanowires of a Si/Ge core/shell nanowire heterostructure and the influence of the structural defects on the electrochemical performances in lithium-ion battery anodes based on Si/Ge core/shell nanowire heterostructures. The induced structural defects consisting of stacking faults and dislocations in the core Si nanowire were observed for the first time. The generation of stacking faults in the Si/Ge core/shell nanowire heterostructure is observed to prefer settling in either only the Ge shell region or in both the Ge shell and Si core regions and is associated with the increase of the shell volume fraction. The relaxation of the misfit strain in the [112] oriented core/shell nanowire heterostructure leads to subsequent gliding of Shockley partial dislocations, preferentially forming the twins. The observation of crossover of defect formation is of great importance for understanding heteroepitaxy in radial heterostructures at the nanoscale and for building three dimensional heterostructures for the various applications. Furthermore, the effect of the defect formation on the nanomaterial's functionality is investigated using electrochemical performance tests. The Si/Ge core/shell nanowire heterostructures enhance the gravimetric capacity of lithium ion battery anodes under fast charging/discharging rates compared to Si nanowires. However, the induced structural defects hamper lithiation of the Si/Ge core/shell nanowire heterostructure.

Photoanodes based on TiO2and α-Fe2O3for solar water splitting – superior role of 1D nanoarchitectures and of combined heterostructures

Solar driven photoelectrochemical water splitting represents a promising approach for a sustainable and environmentally friendly production of renewable energy vectors and fuel sources, such as H₂.

Novel WO3/Sb2S3 Heterojunction Photocatalyst Based on WO3 of Different Morphologies for Enhanced Efficiency in Photoelectrochemical Water Splitting

We report the fabrication of tungsten trioxide (WO3) with different morphologies applied in photoelectrochemical (PEC) water splitting. The antimony sulfide (Sb2S3) was incorporated onto WO3 for the first time with the aim of improving its photoelectrocatalytic activity under visible-light illumination. In the present work, WO3 of different morphologies were fabricated on FTO glass via adjusting the pH value via a facile hydrothermal method and the morphological effect on the photoelectrocatalytic activity of the obtained samples has been discussed. WO3/Sb2S3 heterojunction photoelectrocatalysts were subsequently synthesized successfully to further improve the photoelectrocatalytic activity. Among them, WO3/Sb2S3 heterojunction photoelectrocatalyst based on WO3 micro crystals achieved an enhanced photocurrent of 1.79 mA/cm(2) at 0.8 V versus RHE under simulated sunlight, compared to 0.45 mA/cm(2) of pristine WO3 micro crystals. This excellent PEC performance benefits from the enhanced light absorbance, construction of suitable energy band gap, the improved photogenerated electron-hole pairs separation and transfer efficiency, which potentially provides new insights into PEC water splitting systems.

High-efficiency p–n junction oxide photoelectrodes for photoelectrochemical water splitting

Development of all oxide p–n junctions makes a significant advancement in photoelectrode catalysis functional materials.

Fabrication and photoelectrochemical properties of TiO2/CuInS2/Bi2S3 core/shell/shell nanorods electrodes

The FESEM images (a and b), photocurrent density versus potential (c–v) curves (c) and schematic of the energy level arrangement (d).