Ferroelectric KNbO3 nanoplatelets for thermally driven pyrocatalytic hydrogen evolution and dye degradation

Day- and night-induced thermal cycling offers a promising route for harvesting ambient thermal energy to drive sustainable hydrogen production and pollutant degradation. Pyroelectric materials enable this process by converting temperature fluctuations into surface charges capable of promoting catalytic water splitting and advanced oxidation reactions. In this work, we demonstrate efficient pyrocatalytic hydrogen evolution and Rhodamine B (RhB) degradation using orthorhombic ferroelectric Potassium niobate (KNbO$_3$) nanoplatelets (KN-np). Under thermal cycling between 20 and 50 $^\circ$C, KN-np achieved a hydrogen yield of 680 $\mu$mol g$^{-1}$ after 30 thermal cycles, corresponding to an average hydrogen production rate of 22.67 $\mu$mol g$^{-1}$ per cycle. In addition, KN-np exhibited excellent pyrocatalytic activity toward RhB degradation, reaching 84% removal after only 16 thermal cycles with an apparent kinetic rate constant of 0.11 cycle$^{-1}$. The remarkable catalytic performance is attributed to the strong spontaneous polarization and excellent pyroelectric properties of the KNbO$_3$ nanoplatelets, which promote efficient charge generation and interfacial redox reactions. These findings highlight the potential of KNbO$_3$ nanostructures as efficient pyrocatalysts for clean hydrogen production and environmental remediation.