Borophene Nanosheets Stabilized Ultra‐Low Platinum Nanoclusters: An Efficient Electrocatalyst for Methanol Oxidation Reaction and Hydrogen Evolution Reaction

ABSTRACT In this work, borophene nanosheets stabilized platinum nanoclusters (PtNCs‐BNS) were demonstrated as ultra‐low Pt‐content two‐dimensional (2D) electrocatalyst for the methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER). Here, hydride‐functionalized borophene nanosheets (H‐BNS) are prepared via a sonochemical liquid‐phase exfoliation method using magnesium diboride (MgB 2 ) and water, where the in situ generated protons ( H + ) during the probe sonication process can exchange with magnesium ions, which leads to the formation of a stable functionalized borophene, specifically in H‐BNS. Afterward, it was used as a chemical reducing agent for PtNCs‐BNS synthesis. The PtNCs‐BNS was characterized using X‐rays, spectroscopic, microscopic, and electrochemical analysis, confirming the functionalization, PtNCs (∼2 nm) on the BNS surface, and electrocatalytic activity. Electrochemical studies exhibit excellent electrocatalytic activity in terms of high specific activity (3.7 mA cm −2 ), mass activity (13.7 mA mg −1 ), and CO‐tolerance (I f /I b : 8.2) for MOR. For HER, the benchmark current density of 10 mA cm −2 was achieved at the low overpotential of 0.029 V with a Tafel slope of 30 mV dec −1 vs. the reversible hydrogen electrode (RHE). Besides, the PtNCs‐BNS revealed acceptable stability for both MOR (>200 cycles) and HER (>19 h and >5000 cycles), and also exhibited comparable performances with commercial 20 wt.% Pt.