Bifunctional MXene-Pd multilayer electrodes enabling coupled electrochemical reforming and hydrogen evolution

Abstract

Conventional water splitting requires high overpotentials, whereas electrochemical reforming offers a sustainable route to produce hydrogen while oxidizing alcohols. In this work, we report the rational design of structurally ordered multilayer thin-film electrodes via electrostatic layer-by-layer (LbL) assembly, employing palladium nanoparticles (Pd NPs) as active electrocatalytic sites for both methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER), and MXene as a multifunctional conductive support. The sequential assembly of negatively charged MXene nanosheets and positively charged Pd NPs produced well-defined (MXene/Pd) multilayers, which delivered a high MOR current density of 9.38 mA cm− 2. This performance significantly surpasses that of other Pd-based multilayer electrodes, primarily due to the role of MXene in preventing NPs agglomeration, providing superior electrical conductivity, and, in the case of HER, contributing its own intrinsic hydrogen adsorption-desorption activity, which synergistically enhances the overall catalytic performance together with Pd. Furthermore, in two-electrode full-cell configurations, peak voltages of 0.9 V with a Pt cathode and 0.65 V with a (MXene/Pd) cathode were achieved, both below the theoretical water-splitting voltage of 1.23 V. The cooperative integration of Pd and MXene thus maximizes both methanol oxidation and hydrogen evolution, presenting a viable alternative to Pt-based catalysts. This study highlights the potential of LbL-engineered hybrid electrodes as a scalable and high-performance platform for electrochemical reforming and clean energy applications.