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Formation of the NiCo2O4 (NCO) nanoparticle with the simultaneous reduction of GO and growth of MoS2 by a two step hydrothermal process results in a 2D RGO-MoS2 (R-MoS2) cocatalyst layer with intimate interfacial contact with NCO. The phase purity, chemical coupling and morphology of the synthesized materials are established through X-ray diffraction, Raman and X-ray photoelectron spectroscopy studies. The ternary composite, RGO-MoS2-NiCo2O4 (RM-NCO), shows excellent electrocatalytic performance toward solar driven water splitting with 3.08% solar to hydrogen (STH) conversion efficiency, photocurrent density of 5.36 mA cm–2, injection efficiency of 97% at 1 V (vs Ag/AgCl) and long-term stability. The photo degradation (95%) of Rhodamine B under visible light irradiation is obtained in 90 min by the ternary composite (RM-NCO). The improved performance of the ternary composite, RM-NCO, over bare NCO and MoS2, toward photocatalytic activity is achieved through the dual charge transfer pathway between interfacial layer of NCO and MoS2 to RGO, which leads to generation of more photoinduced charge carriers and suppression of electron–hole recombination process.

We report the photocurrent generation in reduced graphene oxide–cadmium zinc sulfide (RGO–Cd0.75Zn0.25S) nano composite material under simulated solar light irradiation, where the photocurrent increases linearly with increasing incident light intensity. We also report the temperature dependent electrical conductivity and conductivity relaxation in RGO–Cd0.75Zn0.25S composite. At low frequency, the real part of conductivity is independent of frequency, and above a characteristic crossover frequency, the conductivity decreases with the increase in frequency, which indicates the onset of a relaxation phenomenon. The dc conductivity of the RGO–Cd0.75Zn0.25S composite shows Arrhenius behavior. From the scaling of real part of conductivity spectra, we have observed that the dynamic process occurring at different temperatures have the same thermal activation energy. The RGO–Cd0.75Zn0.25S composite shows an enhancement of photo catalytic activity in comparison to control sample under simulated solar light irradiation to degrade Rhodamine B. The RGO sheets prolong the separation of photo induced electrons and holes in Cd0.75Zn0.25S, which hinder the electron–hole recombination and subsequently enhances the photocurrent generation and photocatalytic activity under simulated solar light irradiation.

Reduced graphene oxide (RGO)-supported bismuth ferrite (BiFeO3) (RGO–BFO) nanocomposite is synthesized via a two-step chemical route for photoelectrochemical (PEC) water splitting and photocatalytic dye degradation. The detailed structural analysis, chemical coupling, and morphology of BFO- and RGO-supported BFO are established through X-ray diffraction, Raman and X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy studies. The modified band structure in RGO–BFO is obtained from the UV–vis spectroscopy study and supported by density functional theory (DFT). The photocatalytic degradation of Rhodamine B dye achieved under 120 min visible-light illumination is 94% by the RGO–BFO composite with a degradation rate of 1.86 × 10–2 min–1, which is 3.8 times faster than the BFO nanoparticles. The chemical oxygen demand (COD) study further confirmed the mineralization of an organic dye in presence of the RGO–BFO catalyst. The RGO–BFO composite shows excellent PEC performance toward water splitting, with a photocurrent density of 10.2 mA·cm–2, a solar-to-hydrogen conversion efficiency of 3.3%, and a hole injection efficiency of 98% at 1 V (vs Ag/AgCl). The enhanced catalytic activity of RGO–BFO is explained on the basis of the modified band structure and chemical coupling between BFO and RGO, leading to the fast charge transport through the interfacial layers, hindering the recombination of the photogenerated electron–hole pair and ensuring the availability of free charge carriers to assist the catalytic activity.

To achieve sustainable production of H2 at ambient temperature, highly active and stable electrocatalysts are the key to water splitting technology commercialization for hydrogen and oxygen production to replace Pt and IrO2 catalysts. Herein, a modified interface of palladium (Pd) and reduced graphene oxide (RGO)-supported molybdenum disulfide (MoS2) prepared by the solvothermal followed by chemical reduction method is established, in which abundant interfaces are formed. The phase structure, composition, chemical coupling, and morphology of the two-dimensional nanostructures are established by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy, respectively. A structural phase transformation in MoS2 is observed from trigonal (2H) to octahedral (1T) by virtue of Pd addition, which is well established from XRD, Raman, and XPS studies. For oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), the RGO/MoS2/Pd (RMoS2Pd) catalyst exhibits extremely low overpotential (245 mV for OER and 86 mV for HER) to achieve benchmark current density, with small values of Tafel slope (42 mV dec–1 for OER and 35.9 mV dec–1 for HER) and charge transfer resistance. The quantitative study shows the hydrogen production rate of RMoS2Pd of 335 μmol h–1 with excellent stability in alkaline medium, which is superior to MoS2, RMoS2, and MoS2Pd. The improved performance of RMoS2Pd is attributed to the combined synergetic effect of 1T MoS2, sulfur vacancy, and conducting RGO sheet, which efficiently accelerate the overall electrochemical water splitting.