In the present investigation, facet-controlled Pd nanoparticles with nanocube (PdNC) and truncated octahedron (PdTO) morphologies, and their counterparts with half-a-monolayer of atomic Pt coated (0.5θPt-PdNC and 0.5θPt-PdTO) surfaces were prepared. All of them were characterized and evaluated as cocatalyst after supporting them on commercial titania (P25) (PdNC/P25, PdTO/P25, 0.5θPt-PdNC/P25, and 0.5θPt-PdTO/P25) under direct sunlight and/or one sun conditions for the oxidation of methanol to formaldehyde along with solar hydrogen production. PdNC/P25 shows higher activity for hydrogen generation compared to PdTO/P25; however, activity reversal occurs with the above cocatalysts, but, after Pt-coating with further enhanced activity. The highest conversion of methanol (0.2 μmol/h.mg) to 100% selective formaldehyde was observed with 0.5θPt-PdTO/P25, while other catalysts show significantly lower methanol conversion in the following order: 0.5θPt-PdTO/P25 > 0.5θPt-PdNC/P25 > PdNC/P25 > PdTO/P25. Pt-coated on (111) facets of PdTO simulates the activity associated as that of Pt(111) facets and demonstrating the highest and facet dependent activity. The present study is truly in resonance with exploiting the surface properties for heterogeneous catalysis, and highlights that less than a monolayer of Pt is sufficient to simulate the activity as that of bulk Pt. It is worth exploring this concept to other metals and substrates too.

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Activation of the C−H bond in cyclohexane (CYH) and methane is a crucial step to obtain desirable oxygenated products using nanostructured catalyst and is a great challenge and an efficient route to mitigate the inauspicious effects of climate change. The active sites were identified using XRD, HR-TEM, SEM, N 2 sorption analysis, TPR, Raman, XPS, TGA, in situ DRIFT, XAS, etc. In optimal reaction conditions, 46% of CYH was converted into adipic acid (AA) on Mn x WO 4 nanostructures within 6 h. The recyclability test confirmed the catalyst heterogeneity, which revealed no appreciable loss of catalytic activity even after three consecutive reactions. In situ DRIFT study reveals that CYH is oxidized to cyclohexanone and cyclohexanol (KA oil) and is further oxidized to AA via carboxylate intermediates. DFT studies disclosed that MnOx species are responsible for the C−H activation of CYH, and the Mn 2+/ Mn 3+ redox centers play a vital role in the absorption of KA oil to form AA. Herein, we demonstrated the significant role of the "MnOx" species and that adequate Lewis and Bronsted acidic sites, redox centers of (Mn 2+ /Mn 3+ ), and lattice oxygen are accountable for the CYH conversion toward the AA. Additionally, we have reported the oxidation of methane to methanol (146 μmole per gram of catalyst) in the presence of water at 75 °C without over-oxidation products.

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