Driven by the quest of renewable and clean energy sources, researchers all around the globe are seeking solutions to replace the non-renewable fossil fuels to meet the ever-increasing energy supply...

Cr-doped SnO 2 nanostructures with a dopant concentration ranging from 1 to 5% have been successfully prepared using low-temperature modified solvothermal synthesis. The as-prepared nanoparticles showed a rutile tetragonal structure with a rough undefined morphology having no other elemental impurities. The particle shape and size, band gap, and specific surface area of the samples were investigated by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, UV–visible diffused reflectance spectroscopy, and Brunauer–Emmett–Teller surface area studies. The optical band gap was found in the range of 3.23–3.67 eV and the specific surface area was in the range of 108–225 m 2 /g, which contributes to the significantly enhanced photocatalytic and electrochemical performance. Photocatalytic H 2 generation of as-prepared Cr-doped SnO 2 nanostructures showed improved effect of the increasing dopant concentration with narrowing of the band gap. Electrochemical water-splitting studies also stressed upon the superiority of Cr-doped SnO 2 nanostructures over pristine SnO 2 toward hydrogen evolution reaction and oxygen evolution reaction responses.

The exponential population growth on earth has put an enormous strain on energy resources, which come in various forms like fossil fuels, geothermal energy, and so on. Currently, fossil fuels are fulfilling most of our energy requirements. However, their nonrenewable nature and the production of toxic and greenhouse gases have forced the research community to explore different renewable and nontoxic energy resources. Among different renewable energy resources, hydrogen is considered an important alternative energy source. However, the production of hydrogen (H 2 ) from water is a nonspontaneous process. Therefore, different processes like photocatalysis and photoelectrocatalysis are employed to carry out the water splitting. For these processes, there is a dire need to develop different substances that can act as catalysts. For energy applications, different metals (particularly noble metals) and metal oxides (mostly transition metal oxides) have shown promising catalytic applications in the past decade. Herein, we discuss the progress made in the synthesis of metal and metal oxide nanostructures, followed by a discussion regarding the advances made in the application of these nanostructures as photocatalysts, electrocatalysts, and photoelectrocatalysts. From an energy application standpoint, it is found that doping and heterostructure development are the most advantageous methods used to date to improve the efficiency of metal and metal oxide nanostructures. Also, the development of dye-sensitized metal oxide catalysts for energy applications is considered a powerful method to develop highly efficient photocatalysts and electro-/photoelectrocatalysts. Finally, the limitations and challenges facing the practical application of these nanostructures are also discussed.

Herein, we report a hydrothermal method to synthesize pristine and Agdoped WO 3 nanoplates and study their multifunctional competence in the accomplishment of enhanced catalytic organic conversion and highly efficient photocatalytic and electrocatalytic H 2 evolution reactions. The as-synthesized nanoplates were characterized by using various techniques including X-ray diffraction, field emission scanning electron microscopy-energy-dispersive X-ray analysis, transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and BET surface area studies. The significant catalytic performance was shown by 1% Agdoped WO 3 nanoplates with 100% glycerol conversion and 90% triacetin selectivity. The photocatalytic activity was also examined toward water splitting H 2 evolution reaction which demonstrates the highest H 2 evolution of 12.06 mmol g −1 catalyst for 1% Ag-doped WO 3 nanoplates in a time span of 8 h. Moreover, the electrocatalytic hydrogen evolution reaction was also monitored in acidic media (0.1 M H 2 SO 4 ) which demonstrates good results for 1% Ag-doped WO 3 nanoplates with a low overpotential of 0.53 V and a low Tafel slope of 40 mV dec −1 .

Highly crystalline and monophasic silver nanospheres with a high specific surface area of 57 m 2 /g have been synthesized by an environmentally benign rapid chemical reduction using l -alanine for catalytic transformation, photocatalytic degradation, and bacterial disinfection, which can provide an ample strategy for water remediation. Electron microscopic analysis confirms the spherical morphology of as-prepared silver nanoparticles with an average grain size of 20 nm. Silver nanospheres showed excellent catalytic activity for the catalytic hydrogenation and conversion (95.6%) of 4-nitrophenol to 4-aminophenol. Significant photocatalytic degradation proficiency was also shown for methylene blue (94.5%) and rhodamine B (96.3%) dyes under solar irradiation. The antibacterial behavior of Ala–Ag nanospheres was demonstrated through the disk diffusion antibacterial assay against Gram-positive ( Escherichia coli ) and Gram-negative ( Staphylococcus aureus ) bacteria. Multifunctional efficiency of as-prepared Ala–Ag nanospheres for water remediation has also been established.