Ti2+ and Ti4+ species enriched MXene electrocatalyst for highly efficient hydrogen evolution and oxygen evolution reaction kinetics

Abstract

Searching for cost-effective and highly efficient bifunctional electrocatalyst is imperative for developing an integrated energy harvesting system. 2D MXene, Ti3C2Tx has been reported as a promising candidate for catalysing hydrogen evolution reaction (HER) owing to its fascinating physiochemical properties. However, the search for its potential in field of oxygen evolution reaction (OER) is still lacking due to its sluggish kinetics and high overpotentials. In this work, we present a facile approach to synchronously enhance the bifunctionality of MXene by tuning surface exposed Ti species (Ti4+ and Ti2+) to serve as catalytic centres through in-situ growth of silver nanoparticles (AgNPs). The anchoring of AgNPs modulates the electronic environment of electroactive sites towards optimal adsorption and desorption energies of chemisorbed reaction intermediates through interfacial charge transfer. Moreover, this work enlightens the insightful mechanism behind the deteriorated electrochemical performance upon the agglomeration of AgNPs, confirmed by TEM and XPS results. The optimal electrode delivered a current density of 10 mA cm−2 at overpotential of 0.117 V and 0.25 V for HER and OER, respectively in 0.5 M H2SO4. Therefore, this works provides an exciting new strategy to explore surface Ti species of MXene as effective electroactive sites for achieving significantly enhanced HER and OER reaction kinetics.