Three-phase-boundary Pt in a self-supported MoPt2-MoNi4/Mo2C heterojunction electrocatalyst for highly efficient pH-universal hydrogen evolution reaction

Design of high-performance Pt-based electrocatalysts is significant for hydrogen production through water splitting at pH-universal conditions but still challenging. Herein, the MoPt2-MoNi4/Mo2C three-phase heterojunction is fabricated via simply pyrolyzing hydrothermally resultant Mo-Ni precursor with subsequent galvanic Pt replacement process. It exhibits remarkable and stable hydrogen evolution reaction (HER) performance with impressive mass activity and low overpotential of 53, 77 and 46 mV at the current density of 100 mA cm−2 in alkaline, neutral and acidic media, respectively. Density functional theory calculations illustrate that there are multiple types of Pt sites in the phase of MoPt2 in such three-phase heterojunction, while only the Pt atoms located in the three-phase boundary not only process optimal electronic structure modulated by MoNi4/Mo2C, but also act as highly-active sites for HER. Moreover, downshifted d-band center of Pt triggered by the construction of three-phase MoPt2-MoNi4/Mo2C heterojunction, which regulating the free energy of reactive intermediates sorption and thereby accelerating the entire HER process. This work provides some constructive suggestions to design highly efficient Pt-based heterostructured electrocatalysts towards HER.