IrCo single-atom alloy catalysts with optimized d-band center for advanced alkali-Al/acid hybrid fuel cell

Abstract

Electrochemical energy storage/conversion by utilizing hydrogen (H2) an energy carrier is promising for alleviating the energy crisis. As an emerging H2 production technique, alkali/acid hybrid fuel cell has been reported to exhale H2 and generate electric power spontaneously, which requires highly effective and economically feasible electrocatalysts for cathodic hydrogen evolution reaction (HER). Herein, IrCo single atom alloy catalysts (SAACs) encapsulated in nitrogen-doped carbon nanotubes (IrCo@NCNTs) was prepared as cathode catalyst for alkali-Al/acid hybrid fuel cell (3AHFC). IrCo@NCNTs with low Ir loading of 2.17 wt% exhibits very low overpotentials for HER in pH-wide electrolytes (pH = 0 and 14) and achieves improved mass activity, which are 8 times and 13 times greater than that of Pt/C in acidic and alkaline medium, respectively. Density functional theory (DFT) calculations reveal that the high HER activity derives from the lowing of d-band center by introducing Ir, which is favors to tune the electronic structures, leading to the optimized H⁎ adsorption. The assembled IrCo@NCNTs 3AHFC offers a high power density 176.2 mW cm−2, a high hydrogen production rate of 453.0 L m-2 h−1 with high Faradic efficiency of 99.1%, which can compete with those in commercial 20 wt% Pt/C and most reported platinum-free catalysts.