Exploring the capability of doped nano CuS for efficient hydrogen production during NaBH4 methanolysis

Abstract

Cu_0.98V_0.02S and Cu_0.96V_0.02M_0.02S (M ≡ Co, Mg, Mn, Ni) samples were created using the solid reaction method at low temperature. The search match program X’Pert HighScore Plus was used to identify the different phases in each sample. The phase proportions of the two phases identified, Cu_1.8S and CuS, along with their structural parameters were determined applying Rietveld refinement analysis. The transmittance electron microscope technique revealed that the samples have homogeneous particle morphology with spherical shape and size ranging from 7 to 30 nm. Raman analysis indicates the incorporation of the transition metals inside the copper sulfide lattices replacing Cu substitutional at its different crystallographic sites, at least partially. The optical absorbance spectra of all samples were obtained using the diffuse reflectance technique. All samples have the potential to effectively harness visible light. All samples have two optical band gaps. With the introduction of various metals (Co, Mg, Mn, Ni) to Cu_0.96V_0.02M_0.02S samples, the primary band gap of the Cu_0.98V_0.02S sample is reduced to 1.36, 1.44, 1.31, and 1.41 eV for Co, Mg, Mn, Ni, respectively. The secondary band gap value undergoes minimal variations ranging from 0.63 to 0.66 eV based on the dopant element utilized. The outcomes of experiments on hydrogen evolution involving nano- Cu_0.96V_0.02M_0.02S samples as a catalyst derived from the methanolysis of NaBH₄ process are performed. The impact of Cu_0.96V_0.02Co_0.02S nanoparticles on the hydrogen rate of generation is also determined. The maximum generation rate is detected for the Cu_0.96V_0.02Co_0.02S sample at 50,220 mL min^− 1 g^− 1, which manifested excellent recyclability. The activation energy of Cu_0.96V_0.02Co_0.02S in the methanolysis of NaBH₄ was calculated to be \(\:{E}_{a}=28.13\) kJ/mol applying the Arrhenius equation.