Photocatalytic hydrogen evolution, as an environmental-friendly, energy-saving and simple process, has been widely reported. However, there are some important factors that prohibit practical application of photocatalytic hydrogen production, including the low efficiency of solar energy utilization, and the lack of response in the dark. Temperature fluctuation is a very common phenomenon in our daily life, which is rarely reported for use for hydrogen production. Here we demonstrate direct hydrogen evolution through the harvesting of cold–hot 298–323 K (25–50 °C) alternation energy by using pyroelectric nanomaterial Ba_0.7Sr_0.3TiO₃ (BST). The yield of hydrogen achieved was 46.89 μmol per gram of catalyst after 36 thermal cycles and the rate of hydrogen generation was up to 1.30 μmol g⁻¹ per thermal cycle. The minimum of the conduction band of BST is more negative than the conduction band level of H⁺/H₂, enabling the reduction of water to form hydrogen. This efficient and eco-friendly pyro-catalytic method provides a promising future for hydrogen evolution utilizing natural cold–hot temperature fluctuation energy.

High piezoelectric and ferroelectric properties have been found in Mn-doped ${\text{Na}}_{0.5}{\text{Bi}}_{0.5}{\text{TiO}}_3–{\text{BaTiO}}_3$ single crystals, which were grown by a top-seeded solution method. The electrical resistivity, dielectric constant, and ferroelectric and piezoelectric properties were all found to be notably enhanced by Mn. The piezoelectric constant $d_{33}$ and electromechanical coupling coefficients $k_t$ and $k_{31}$ were found to be as high as 483 pC/N, 0.56, and 0.40, respectively. These values are much higher than those previously reported for Pb-free piezoelectric crystals, demonstrating the real potential for alternative lead-free systems for sensor and piezoelectric applications.

The [001]-oriented Pb(Mg_1/3Nb_2/3)O₃-0.25PbTiO₃(PMN-0.25PT) single crystal has been poled by alternating current polarization (ACP). The piezoelectric, dielectric, and electromechanical properties of PMN-0.25PT crystals were investigated with the variations of the electric field, polarization frequency, and cycles. For the piezoelectric performance of the PMN-0.25PT crystal, the optimum ACP condition was obtained under the electric field of 12–18 kV/cm in the frequency range of 20–40 Hz and after 20 cycles. It gives the crystals an increase by 40% from 1220 pC/N to 1730 pC/N in the piezoelectric coefficient compared with traditional direct current polarization. The patterns of the periodic stripe nanodomains under different polarization conditions were revealed by piezoresponse force microscopy. The enhancement of the piezoelectric performance is attributed to the high density of these domain walls. This work indicates that ACP is an effective way to modify the piezoelectric performance of PMN-0.25PT crystals and make it a promising candidate for sensors and transducers.