Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H₂). In the present study, hydrogen (H₂) production efficiency of three promising photocatalysts (titania (TiO₂-P25), graphitic carbon nitride (g-C₃N₄), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO₂-P25, g-C₃N₄, and CdS. H₂ production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H₂ generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H₂ was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.

Ultrafine cerium oxide (CeO₂) nanoparticles have been confirmed to be capable photocatalysts for environmental remediation because of their strong redox ability, long-term stability, nontoxicity, and cost effectiveness. CeO₂ nanoparticles were successfully synthesized by a solution combustion method using cerium nitrate and urea. The physical, chemical, thermal and optical properties of the as-prepared samples were characterized using various analytical techniques. X-ray diffraction data confirm that the synthesized nanocrystalline CeO₂ samples have cubic structure with an average grain size of 10, 8 and 19 nm corresponding to as-prepared, 300 and 600 °C annealed samples, respectively. The HRTEM results confirmed that the synthesized nanoparticles exhibit good polycrystalline nature with spherical ultrafine nanoparticles having size in the range of ∼9 nm. The UV/vis spectrum shows a maximum absorption at 294 nm and the band gap of CeO₂ was tuned by adjusting the annealing temperature. In the PL spectra, a strong and broad emission band was observed at 425 nm due to the presence of a blue shift in the visible region. The photocatalytic activities of annealed CeO₂ nanoparticles were investigated by photodegradation of methylene blue (MB) under UV light irradiation. It was found that the ultra-fine CeO₂ nanoparticles exhibited better photocatalytic activity than that of already available commercial photocatalysts. Based on the investigation, these ultra-fine CeO₂ nanoparticles possess adaptable potential applications for wastewater purification.

Water electrolysis is considered one of the major sources of green hydrogen as the fuel of the future. However, due to limited freshwater resources, more interest has been geared toward seawater electrolysis for hydrogen production. The development of effective and selective electrocatalysts from earth-abundant elements for oxygen evolution reaction (OER) as the bottleneck for seawater electrolysis is highly desirable. This work introduces novel Pd-doped Co nanoparticles encapsulated in graphite carbon shell electrode (Pd-doped CoNPs@C shell) as a highly active OER electrocatalyst towards alkaline seawater oxidation, which outperforms the state-of-the-art catalyst, RuO₂. Significantly, Pd-doped CoNPs@C shell electrode exhibiting low OER overpotential of ≈213, ≈372, and ≈ 429 mV at 10, 50, and 100 mA/cm², respectively together with a small Tafel slope of ≈ 120 mV/dec than pure Co@C and Pd@C electrode in alkaline seawater media. The high catalytic activity at the aforementioned current density reveals decent selectivity, thus obviating the evolution of chloride reaction (CER), i.e., ∼490 mV, as competitive to the OER. Results indicated that Pd-doped Co nanoparticles encapsulated in graphite carbon shell (Pd-doped CoNPs@C electrode) could be a very promising candidate for seawater electrolysis.

A facile solution processing strategy has been developed for the formation of Ag-modified ZnO microneedles at various calcination temperatures such as 300, 500, and 700 °C (AZ3, AZ5, and AZ7 respectively). Due to the heavy doping of AgNO₃, Ag⁺ ions have been incorporated in to the crystal lattice of ZnO in all the Ag-ZnO samples, which facilitated the formation of Ag-ZnO microneedle morphology with minimized defect states, and obviously, the plasmon peaks were observed due to Ag modification. These Ag-ZnO microneedle structures have been evaluated for their photocatalytic performance using methylene blue as model target contaminant and their activity was compared with the commercially available titania P25 photocatalyst. The photoactivity of all the Ag-ZnO microneedle structures was significantly higher than that of the commercially available P25 photocatalyst with the most active Ag-ZnO material having a photocatalytic activity ~ 1.4 times greater than that of P25 titania.