Interfacial optimization of PtNi octahedrons@Ti3C2MXene with enhanced alkaline hydrogen evolution activity and stability

Abstract It remains a great challenge to balance the activity and stability of platinum and Pt-based hydrogen evolution reaction (HER) catalysts in alkaline electrolyte. Herein, two-dimension monolayer Ti3C2 MXene sheets were introduced to support PtNi octahedrons (PtNi@Ti3C2 MXene), which optimizes the activity and stability of PtNi nanoparticles (NPs) through interface interactions between PtNi and Ti3C2 MXene. It shows a small overpotential of 36 mV with a Tafel slope of 59 mV dec−1 at 10 mA cm-2 in 1 M KOH. It also exhibits excellent mass activity of 6.31 mA μgPt-1 at an overpotential of 70 mV, which is ∼7.1 times that of commercial Pt/C and better than many recent reported Pt-based alkaline HER catalysts. Meanwhile, the PtNi@Ti3C2 MXene gives an increased overpotential of ∼4 mV while the PtNi gives ∼25 mV during a long-time continuous CV cycles. A series of characterizations disclose these interfaces could promote the stability by alleviating the Ni atoms dissolution from surficial PtNi through uniformly lattice strain dispersion of PtNi. Simultaneously, they could keep the activity by interfacial electron transfer from PtNi to Ti3C2 MXene demonstrated both by experimental tests (UPS, electrostatic potential and charge density distribution) and DFT calculation. It could decrease the energy barrier of H2O adsorbing and dissociating into hydrogen intermediates, further accelerating the recombination of hydrogen intermediates to H2. Under acidic and neutral medium, the electrocatalyst also exhibits improved HER performance compared to its counterparts. This work provides an interface optimization route for developing high-efficiency pH-universal especially alkaline HER electrocatalysts.