Highly stable PdO nanostructures self-supported on conductive polyaniline nanotubes enable extensive electrochemical hydrogen evolution

Abstract

The quest to meet global energy requirements through the development of stable and cost-effective electrocatalysts that promote the hydrogen evolution reaction (HER), has gained tremendous interest. The modulation of electrocatalyst–electrolyte interaction is a pivotal step towards achieving enhanced HER performances. The present work emphasizes the design of a distinctly stable polymer–metal nanostructure, aiming to accelerate hydrogen production by tuning the active electronic environment of the conducting polymer, which serves as a site-selective platform for the nanoparticles. Spatially uniform and confined palladium oxide nanoparticles (PdO-NPs) were integrated on the surface of symmetrical organic acid doped polyaniline nanotubes (PANI_NTs) to generate a hybrid catalyst. Repeating amine sites provided a uniform platform for the adsorption/formation of PdO-NPs, and subsequent electronic structure modification of active Pd sites resulted in enhanced electrocatalytic activity. After optimization, the hybrid catalyst exhibited a low overpotential of 67 mV at 10 mA cm⁻² current density and remarkable stability for 15 000 accelerated degradation test (ADT) cycles with negligible depletion (1.36%) compared with a commercially available Pd/C catalyst (76.09% depletion after 6000 ADT cycles) in 0.5 M H₂SO₄. Chronoamperometric studies utilising a custom-designed electrochemical flow cell demonstrated the long-term durability (>100 h) of the catalyst with higher current density (350 mA cm⁻²). Through controlled experiments, including electrochemical studies, X-ray photoelectron spectroscopy, and in situ infrared spectroscopy, the driving force behind the remarkable performance was identified by mapping the active sites, charge transfer kinetics and reaction mechanisms; the conclusions were further substantiated by first-principles based DFT calculations.