Composition-Tuned Piezoelectricity Governs Hydrogen Evolution in Ba_1-xSr_xTiO₃ (0 ≤ x ≤ 0.3)

Piezocatalysis is an innovative, clean catalytic technology. The efficiency requires enhancement due to the low level of piezoelectricity, low carrier concentration, and rapid recombination rates of the materials. Composition modulation is a critical strategy for enhancing the piezoelectric activity of ferroelectric materials. In this work, the influence of composition changes on the piezocatalytic performance of barium strontium titanate (Ba_1-xSr_xTiO₃ (0 ≤ x ≤ 0.3)) with varying Ba/Sr molar ratios is investigated. As the Sr content (x) increases from x = 0 to x = 0.3, the effective piezoelectric coefficient exhibits a significant enhancement from d_eff = 46.8 pm·V⁻¹ to d_eff = 205.6 pm·V⁻¹, leading to an increase in the carrier concentration increase (ΔN_d), due to the application of vibrations from ΔN_d = 0.11 × 10²⁰ cm⁻³ (for x = 0) to ΔN_d = 1.69 × 10²⁰ cm⁻³ (for x = 0.3). The optimal hydrogen production for each composition occurs near, but not exceeding, its Curie point (T_C）. The optimized piezocatalytic hydrogen production (per unit power) of Ba_0.7Sr_0.3TiO₃ at room temperature is 53.4 µmol·g⁻¹·h⁻¹·W⁻¹, which is one of the highest reported values to date. This work investigates the fundamental reasons behind composition modulation of piezocatalysis, providing constructive guidance for designing optimized piezocatalysts.