Switchable polarization in ferroelectric catalysts shows promise to overcome the Sabatier limit imposed on traditional catalysts. However, a comprehensive understanding of the polarization effect on electrocatalytic performance remains elusive. In this study, using ferroelectric BaTiO₃ (BTO) as a model system, we report tunable hydrogen evolution reaction (HER) performance governed by polarization states. Based on first-principles calculations, we find that BTO with in-plane polarization shows improved HER activity, in contrast to that with out-of-plane polarization, which is linked to in-plane dipole–dipole interaction at the surface. Interestingly, surface rumpling induced by surface relaxation and polarization states plays an important role in determining surface polarization, which significantly affects the chemical reactivity of surface oxygen. We unravel that the favorable p-band center of surface oxygen is responsible for the enhanced HER activity of in-plane polarized BTO. We further propose the HER catalytic cycle at the BTO surface to break the Sabatier limit via applying controllable polarization states. This work provides an inspiring insight into tunable ferroelectric catalysis by modulating polarization states toward robust HER and beyond.

Multilevel resistive switching in memristive devices is vital for applications in non-volatile memory and neuromorphic computing. In this study, we report on the multilevel resistive switching characteristics in SnSe/SrTiO₃(STO) heterojunction-based memory devices with silver (Ag) and copper (Cu) top electrodes. The SnSe/STO-based memory devices present bipolar resistive switching (RS) with two orders of magnitude on/off ratio, which is reliable and stable. Moreover, multilevel state switching is achieved in the devices by sweeping voltage with current compliance to SET the device from high resistance state (HRS) to low resistance state (LRS) and RESET from LRS to HRS by voltage pulses without compliance current. With Ag and Cu top electrodes, respectively, eight and six levels of resistance switching were demonstrated in the SnSe/SrTiO₃ heterostructures with a Pt bottom electrode. These results suggest that a SnSe/STO heterojunction-based memristor is promising for applications in neuromorphic computing as a synaptic device.