Investigating the structure, optical, and catalytic performance of Sn0.95M0.05S (M = Fe or Co) nanoparticles for hydrogen generation
摘要
Nano SnS and Sn0.95M0.05S (M = Fe or Co) samples were synthesized via thermal evaporation technique in a nitrogen atmosphere. X-ray diffraction patterns revealed a single-phase SnS with an orthorhombic structure, imposing incorporation of Fe and Co into the SnS lattice. Variations of the lattice parameters, crystallite size, and lattice micro-strain were determined using Rietveld refinement analysis. The SEM images obtained disclosed two-dimensional sheets that are densely aggregated in structural building blocks. The samples have a nanosheet with a smooth texture, with a predominant plate-like morphology. The diffuse reflectance spectrum of the SnS sample was affected by the type of dopant (Fe or Co) and the wavelength range. SnS, Sn0.95Co0.05S, and Sn0.95Fe0.05S samples have optical band gap values of 1.11, 1.14, and 1.13 eV, respectively. The slow kinetics of NaBH4 hydrolysis were markedly enhanced by employing SnS particles as a catalyst, resulting in a rise in the rate of H2 volume generated from 152.1 to 280.8 mL (g−1 min−1). The addition of 5% Co to SnS markedly enhanced the generation of hydrogen, achieving a rate of 490 mL (g−1 min−1), about double that of pure SnS and triple that of NaBH4 self-hydrolysis. The thermodynamic parameters and activation energy (Ea) were examined to elucidate the mechanism underlying the catalytic activity. The activation energy of Sn0.95Co0.05S toward NaBH4 is 47.84 kJ mol−1 and the calculated values of ΔH‡, ΔS‡, and ΔG‡ are 45.09 kJ mol−1, − 73.81 J K−1, and 69.23 kJ mol−1, respectively. The enthalpy of adsorption ΔHads is determined as 2.75 kJ mol−1. The positive value of ΔHads implies that the adsorption process is endothermic in nature and the negative ΔS‡ value demands that Sn0.95Co0.05S exhibited a Langmuir–Hinshelwood associative mechanism.