To address aggravating environmental and energy problems, active, efficient, low-cost, and robust electrocatalysts (ECs) are actively pursued as substitutes for the current noble metal ECs. Therefore, in this study, we report the preparation of graphene flakes (GF) doped with S and N using 2-5-dimercapto-1,3,4-thiadiazole (S3N2) as precursor followed by the immobilization of cobalt spinel oxide (Co3O4) or manganese spinel oxide (Mn3O4) nanoparticles through a one-step co-precipitation procedure (Co/S3N2–GF and Mn/S3N2–GF). Characterization by different physicochemical techniques (Fourier Transform Infrared (FTIR), Raman spectroscopy, Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD)) of both composites shows the preservation of the metal oxide spinel structure and further confirms the successful preparation of the envisaged electrocatalysts. Co/S3N2–GF composite exhibits the best ORR performance with an onset potential of 0.91 V vs. RHE, a diffusion-limiting current density of −4.50 mA cm−2 and selectivity for the direct four-electron pathway, matching the results obtained for commercial Pt/C. Moreover, both Co/S3N2–GF and Mn/S3N2–GF showed excellent tolerance to methanol poisoning and good stability.

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Metal chalcogenides such as copper zinc tin sulfide (CZTS) have been intensively studied as potential photovoltaic cell materials, but their viability have been marred by crystal defects and low open circuit potential (Voc) deficit, which affected their energy conversion efficiency. Strategies to improve on the properties of this material such as alloying with other elements have been explored and have yielded promising results. Here, we report the synthesis of CZTS and the partial substitution of S with Te via anion hot injection synthesis method to form a solid solution of a novel kesterite nanomaterial, namely, copper zinc tin sulfide telluride (CZTSTe). Particle-size analyzed via small angle X-ray scattering spectroscopy (SAXS) confirmed that CZTS and CZTSTe materials are nanostructured. Crystal planes values of 112, 200, 220 and 312 corresponding to the kesterite phase with tetragonal modification were revealed by the X-ray diffraction (XRD) spectroscopic analysis of CZTS and CZTSTe. The Raman spectroscopy confirmed the shifts at 281 cm−1 and 347 cm−1 for CZTS, and 124 cm−1, 149 cm−1 and 318 cm−1 for CZTSTe. High degradation rate and the production of hot electrons are very detrimental to the lifespan of photovoltaic cell (PVC) devices, and thus it is important to have PVC absorber layer materials that are thermally stable. Thermogravimetric analysis (TGA) analysis indicated a 10% improvement in the thermal stability of CZTSTe compared to CZTS at 650 °C. With improved electrical conductivity, low charge transfer resistance (Rct) and absorption in the visible region with a low bandgap energy (Eg) of 1.54 eV, the novel CZTSTe nanomaterials displayed favorable properties for photovoltaics application.