PANI/MXene/MnO2 ternary heterostructure with multi-redox active sites and enhanced interfacial charge transfer for efficient hydrogen production via electro/photocatalytic water splitting

Abstract

The present study is focused on exploring strategies for enhancing electrocatalytic and photocatalytic water splitting kinetics by increasing the density of potential redox-active sites, promoting higher charge separation, and inhibiting self-corrosion during prolonged light-exposure in photocatalysis. In this regard, a highly efficient ternary heterostructure PANI/MXene/MnO₂ (PMM) catalyst was prepared via in-situ polymerization of PANI on MXene/MnO₂ composite and then loaded onto flexible carbon fibre (CF) support using a facile dip-coating method. The obtained PMM/CF heterostructure reveals superior activity in electrochemical water splitting, requiring an overpotential of merely 67 mV and 170 mV to drive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, along with a small cell voltage of 1.49 V, contrary to pristine MXene which exhibits high overpotential of 206 mV for HER and remains inactive in OER. Further, in photocatalysis, PMM/CF combined with CdS photo absorber reveals a high photocurrent density of 9.87 mA cm⁻² and photoconversion efficiency of 0.41% due to maximized light absorption and quick charge separation facilitated by a Z-scheme route charge transfer. Thus, this work led to the development of a robust hydrogen-evolving electrode that collectively operates for electrocatalysis and sunlight-driven photocatalysis for sustainable hydrogen production.