Nicop Anchored Porous Ti3C2tx Support with 3D Interconnected Structure for Advanced Hydrogen Evolution Reaction Electrocatalysts

Abstract

MXene have gained much attention as promising electrocatalysts for noble metal-free hydrogen evolutrion reaction (HER) electrocatalysts owing to their high electrical conductivity, hydrophilic surfaces, abundant functional groups, and rational design for hybridization with other materials. In this study, a novel porous monolayered-Ti3C2TX@NiCoP (P-Ti3C2Tx@NiCoP) nanostructure was developed with 3D interconnected structure to significantly improve charge transfer capability and electrocatalytic activity. A strategic approach of modifying pristine Ti3C2Tx monolayers and combining them with other active cocatalysts. Specifically, the H2O2-utilized oxidation and HF etching process formed a highly microporous structure with a maximized surface area of monolayered MXenes as the support. A subsequent solvothermal process followed by phosphidation enabled successful anchoring of highly HER-active NiCoP nanoclusters onto abundantly exposed terminal edges of the P-Ti3C2Tx support. The structural porosity of the P-Ti3C2Tx nanoflakes played an important role in creating additional room for embedding catalytically active species while stably imparting high electrical conductivity to accelerate charge transfer to NiCoP nanoclusters. Moreover, inspired by the pH dependent change of structural arrangement of the Ti3C2Tx, we successfully induced 3D-interconnetecd structure by modulating surface electrostatic forces among Ti3C2Tx monolayers. Of note, the 3D-interconnected structure would shift charge transfer behavior from intermolecular to intramolecular aspects and this would contribute to enhanced charge transfer kinetics. With structural modification of support material and effective hybridization of active species, P-Ti3C2Tx@NiCoP showed highly enhanced HER activity with significantly lower overpoential of 115 and 101 mV at a current density of -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, along with showing long-term stability over 60 h. As such, our approach of designing structurally modified-Ti3C2Tx and hybridization with other electrocatalytically active species would function as a solid platform for implementing Ti3C2Tx-based hetero-nanostructures to achieve state-of-the-art performance in next-generation energy conversion applications.