Unravelling the Origin of Enhanced Electrochemical Performance in CoSe2-MoSe2 Interfaces

Defect and interface engineering have been shown as effective strategies towards sustainable hydrogen production, but detailed descriptions of the origin of performance enhancements is not established. Here, we synthesize a model heterostructure interface, CoSe2-MoSe2/PEDOT, to unravel its bifunctional capability. Low eta(10) of -0.20 V for HER and 1.53 V for OER verified the electrocatalytic performance of this catalyst. We systematically reveal intrinsic point defects and lattice dislocations in these heterostructures. Atomic scale electron microscopy studies disclose presence of V-Se and Mo-Mo bond defects. Spectroscopic techniques are employed to show the altered electronic properties that promote surface oxidation due to the presence of defects. In contrast to MoSe2 or MoSe2/PEDOT, defect rich CoSe2-MoSe2/PEDOT showed accelerated reaction kinetics with much lower Tafel slopes. Essentially, generation of anion vacancies and metallic Mo-Mo bonds provide additional sites with improved adsorption properties of the reaction intermediates. This catalyst exhibits excellent electrocatalytic stability upon cycling for both half-cell reactions.