The effective harnessing of hydrogen energy relies on the development of bifunctional electrocatalysts that facilitate hydrogen evolution/oxidation reactions (HER/HOR) with high catalytic activity. The design of such electrocatalysts requires the consideration of not only the volcano relationship with hydrogen binding energy (HBE) or hydrogen adsorption Gibbs free energy (ΔGH) but also the regulation of catalytic kinetics such as interfacial proton/electron transfer. In this work, unique one-dimensional iridium nanowires with compressive stress are successfully prepared and combined with carbon dots (Ir NWs/CDs). Acting as an electrocatalyst for HER in 0.5 M H2SO4, the optimal Ir NWs/CDs only requires an 18 mV overpotential to achieve a current density of -10 mA cm-2. Furthermore, the optimal Ir NWs/CDs shows high HOR performance with a mass activity (@ 50 mV versus RHE) 1.5 times that of 20% Pt/C and excellent anti-CO toxicity ability which is twice the level of the PtRu/C catalyst. Ir NWs/CDs exhibit enhanced HER/HOR activity due to (1) the appropriate modulation of the binding energy to hydrogen intermediate facilitated by the compressive stress applied to the Ir structure and (2) the improved proton/electron transfer kinetics by optimizing the electronic properties and surface structures through tailored CDs. This study delivers a new strategy for designing and synthesizing efficient acidic HER/HOR bifunctional catalysts.
Keywords: Bifunctional catalyst; Carbon dots; Hydrogen evolution reaction; Hydrogen oxidation reaction; Lattice strain.
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