Synergetic coupling of Pd nanoparticles and amorphous MoSx toward highly efficient electrocatalytic hydrogen evolution reactions

Noble metal palladium (Pd) has been widely used in hydrogen-related catalytic reactions. However, its performances toward hydrogen evolution reactions (HER) are intrinsically restricted due to a strong bonding of Pd-H thus make the hydrogen desorption difficult. In this work, being as an electron-cocatalyst, Pd nanoparticles are anchored on our well-established amorphous MoSx/TiO2 nanotube arrays (TNAs) electrocatalyst system through an electrochemical deposition technique. The unique electronic structure in the S-vacancies and/or unsaturated S atoms of MoSx significantly weaken the Pd-H bonding in the electrocatalytic process, facilitating the hydrogen desorption process. In the meantime, conductivity of MoSx/TNAs is largely improved due to incorporation of Pd nanoparticles into the system, which enables the charge transfer from electrode to active site of MoSx more efficient. The synergetic coupling of Pd and MoSx/TNAs result in a superior electrocatalytic activity, achieving an onset overpotential of −29 mV, overpotentials of −64 and −88 mV at −10 and −20 mA cm−2, which are equivalent to that from Pt catalysts.