MBene Brønsted Acid Catalyst for Hydrogen Evolution Reaction in Alkaline Electrolyte

Abstract

Surface-chemistry tailoring of the catalyst is rather meaningful for activity improvement in the electrocatalytic alkaline hydrogen evolution reaction (HER) for hydrogen production. Herein, we report a mild organic-base-driven intercalation and delamination of bulk MoAlB powder into two-dimensional (2D) nanosheets (MBenes) by taking advantage of the amphoteric nature of interlayer Al atoms. In contrast to the conventional oxygen-containing group (e.g., O and OH) coated 2D MBenes by fully removing the interlayer Al⁰ atoms in strong alkaline solutions, abundant unusual Al³⁺ oxyanions (AlO_x^–) are uniformly decorated on our well-designed organic-alkali-exfoliated 2D MBene surface. Accordingly, the as-obtained Al-rich MBene catalyst exhibits a superior alkaline HER activity with a low overpotential (130 mV) at the typical current density of 10 mA/cm² and a small Tafel slope (58 mV/dec), nearly 4.6- and 2.2-fold enhancements compared to those of the conventional MBene counterpart, respectively. Comprehensive spectroscopy characterizations and DFT calculations demonstrate that the bridging oxygen atoms in local −Al–O–Mo– structures possess strong Brønsted acid nature with reversible behavior in proton storage and donation, which generally benefits the proton-coupled electron HER process in alkaline electrolyte. Our work may pave an interesting route to design 2D Brønsted acid nanosheets for highly efficient water electrolysis and beyond.