In-situ synthesis of Cr2O3-enhanced bifunctionality in walnut-like Pt/CrN for methanol-assisted high-efficiency hydrogen generation

Abstract

Methanol-assisted water electrolysis offers a promising alternative for low-voltage green hydrogen generation. Herein, we report the design and in-situ synthesis of Cr2O3, achieved by pyrolyzing a coordination polymer, to serve as cocatalysts. The Cr2O3 cocatalyst enhances the bifunctionality of the walnut-like Pt/CrN catalyst, leading to remarkable electrocatalytic activity in the methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) compared to Pt/CrN catalyst. Experimental data confirmed that Cr2O3 as a promoter accelerates the water dissociation, resulting in the formation of OHad. Additionally, it reduces the d-band center of Pt, favoring the optimization of the Gibbs free energy of intermediates. Moreover, the walnut-like Cr2O3–CrN facilitates mass diffusion and electron transfer. The synergistic effect between Cr2O3 and CrN, along with the presence of a hetero-interface, contributes to the enhancement of MOR/HER electrocatalytic activity. Thanks to these advantageous characteristics, the as-prepared Pt/Cr2O3–CrN catalysts exhibit superior MOR/HER performance, achieving a mass activity of 1.425 A mgPt−1 for MOR and an overpotential of 42 mV at a current density of 10 mA cm−2. Furthermore, with the Pt/Cr2O3–CrN as a bifunctional catalyst for both MOR and HER, the methanol-assisted electrolyzer only requires a cell voltage of 0.628 V to deliver a current density of 10 mA cm−2 for 10 h.