Insight into the catalytic performance of HER catalysis of noble metal/3D-G nanocomposites

Abstract Development of multifunctional materials has shown a great interest in recent years. Herein, we report the simple, cost-effective, one step, and surfactant-free synthesis of three-dimensional graphenes (3D-G) nanocomposites with Pt, Pd, Au and Ag and explore their catalytic activity and investigated the dynamics for the hydrogen evolution reaction (HER). Field emission scanning electron microscopy (FEG-SEM) and high resolution transmission electron microscopy (HRTEM) study reveals the uniform incorporation of noble metal on the 3D-G. The 3D-G with Pt composite (Pt/3D-G) has shown significantly enhanced catalytic performance over the commercially available Pt/C for HER, suggesting significant improvements in catalytic performance on the incorporation of 3D-G. The Temperature dependent HER investigation has been performed and the apparent activation energy (Eaapp) for Pt/3D-G. Pd/3D-G, Au/3D-G, and Ag/3D-G catalysts are obtained as 25.37, 32.36, 16.14, and 24.82 kJ/mol, respectively. Eaapp of Pt/3D-G and Pd/3D-G are found to decrease with increase in the overpotential, and the Eaapp of Au/3D-G and Ag/3D-G is found to increase with overpotential. This variation of Eaapp with the applied potential is correlated with the metal-hydrogen bond energy with respect to the potential of zero charges (PZC). The kinetics of HER on catalysts is explained in terms of temperature variation of the Tafel slope. The Tafel slopes of Pt/3D-G and Pd/3D-G are increased with increase in temperature, and for Au/3D-G and Ag/3D-G, the Tafel slopes are decreased with increase in temperature, which suggests the enthalpy driven process for Pt/3D-G and Pd/3D-G and entropy driven process for Au/3D-G and Ag/3D-G.