High-performance SrO–Co3O4 nanoparticles anchored on rGO for clean energy: hydrogen generation from formic acid and photocatalytic dye degradation

Abstract

SrO–Co₃O₄ nanoparticles loaded on reduced graphene oxide (SrO–Co₃O₄@rGO) were synthesized through a facile impregnation-reduction route. Physicochemical characterization was conducted to demonstrate the successful synthesis and the structure-property relationship of the catalyst. The catalysts were characterized using UV-Vis spectroscopy, from which their optical band gap was estimated. The SrO–Co₃O₄@rGO composite also exhibits enhanced visible-light absorption behavior compared with GO, implying greater visible-light adsorption capability. Moreover, the maximum absorption peak shifted from 270 to 260 nm, indicating that there was a little blue shift, which could be due to the result of electronic interactions between rGO and SrO–Co₃O₄ species. The crystalline phases of SrO, Co₃O₄, and rGO were characterized by XRD, and the well-distributed nanoparticle distribution on rGO sheets was determined by SEM-EDX. FT-IR confirmed the presence of metal-anchoring functional groups, and TGA showed good thermal stability of the graft. The Brunauer–Emmett–Teller (BET) test showed a mesoporous structure, a large surface area, and an appropriate pore-size distribution suitable for improved mass diffusion. Catalytic analysis of formic acid (FA) dehydrogenation yielded enhanced hydrogen evolution rates, and the highest apparent turnover frequency (TOF) was 5881.1 h⁻¹ under mild conditions. The reaction kinetics followed pseudo-first-order behavior, and the activation energy (E_a) was determined to be 37.34 kJ mol⁻¹. Moreover, the SrO–Co₃O₄@rGO photocatalyst was also more active towards methylene blue (MB) degradation and followed pseudo-first-order kinetics with an activation energy of 10.8 kJ mol⁻¹. The results of the radical scavenging experiments suggested that O₂˙⁻ and photogenerated holes h⁺ were the main reactive species. The rGO support may facilitate interfacial electron transfer, thereby facilitating directional charge transport and reducing recombination. The combined effects of SrO and Co₃O₄ present promising dual-function catalytic properties in SrO–Co₃O₄@rGO for clean energy generation and wastewater treatment.