Aiming to achieve enhanced photocatalytic activity and stability toward the generation of H₂ from water, we have synthesized noble metal-free core-shell nanoparticles of graphene (G)-wrapped CdS and TiO₂ (CdS@G@TiO₂) by a facile hydrothermal method. The interlayer thickness of G between the CdS core and TiO₂ shell is optimized by varying the amount of graphene quantum dots (GQD) during the synthesis procedure. The most optimized sample, i.e., CdS@50G@TiO₂ generated 1510 µmole g⁻¹ h⁻¹ of H₂ (apparent quantum efficiency (AQE) = 5.78%) from water under simulated solar light with air mass 1.5 global (AM 1.5G) condition which is ~2.7 times and ~2.2 time superior to pure TiO₂ and pure CdS respectively, along with a stable generation of H₂ during 40 h of continuous operation. The increased photocatalytic activity and stability of the CdS@50G@TiO₂ sample are attributed to the enhanced visible light absorption and efficient charge separation and transfer between the CdS and TiO₂ due to incorporation of graphene between the CdS core and TiO₂ shell, which was also confirmed by UV-vis, photoelectrochemical and valence band XPS measurements.

Nitric acid (HNO₃) is an important building block in the chemical industry. Industrial production takes place via the Ostwald process, where oxidation of NO to NO₂ is one of the three chemical steps. The reaction is carried out as a homogeneous gas phase reaction. Introducing a catalyst for this reaction can lead to significant process intensification. A series of LaCo_1−xMn_xO₃ (x = 0, 0.25, 0.5 and 1) and LaCo_1−yNi_yO₃ (y = 0, 0.25, 0.50, 0.75 and 1) were synthesized by a sol-gel method and characterized using N₂ adsorption, ex situ XRD, in situ XRD, SEM and TPR. All samples had low surface areas; between 8 and 12 m²/g. The formation of perovskites was confirmed by XRD. The crystallite size decreased linearly with the degree of substitution of Mn/Ni for partially doped samples. NO oxidation activity was tested using a feed (10% NO and 6% O₂) that partly simulated nitric acid plant conditions. Amongst the undoped perovskites, LaCoO₃ had the highest activity; with a conversion level of 24.9% at 350 °C; followed by LaNiO₃ and LaMnO₃. Substitution of LaCoO₃ with 25% mol % Ni or Mn was found to be the optimum degree of substitution leading to an enhanced NO oxidation activity. The results showed that perovskites are promising catalysts for NO oxidation at industrial conditions.