Harvesting the vibration energy of Ba0.95Ca0.05Ti0.9Sn0.1O3/g-C3N4 Z-scheme heterojunctions for nitrogen fixation

Abstract

Piezocatalytic nitrogen fixation is one of the promising technologies for harvesting vibration energy to achieve direct nitrate synthesis from nitrogen. Herein, a novel plate-like composite catalyst of Ba_0.95Ca_0.05Ti_0.9Sn_0.1O₃/x wt% g-C₃N₄ is designed and prepared through a synergistic strategy combining optimization of the morphotropic phase boundary (MPB) and the construction of Z-type heterojunctions for producing nitrate. Under sacrificial-agent-free conditions, Ba_0.95Ca_0.05Ti_0.9Sn_0.1O₃/10 wt% g-C₃N₄ achieves the highest NO₃⁻ production activity of 1.40 mg g⁻¹ h⁻¹, which is 3.9 and 5.3-fold higher than that of pristine Ba_0.95Ca_0.05Ti_0.9Sn_0.1O₃ and g-C₃N₄, respectively. The remarkable catalytic improvement originates from the synergistic effects of enhanced electron–hole pair separation efficiency and improved nitrogen adsorption/activation capabilities achieved through the rational construction of Z-scheme heterojunctions. Multiple techniques including XRD, FTIR, SEM, XPS, UV-vis DRS, PFM, EIS, EPR and in situ XPS were used to reveal the origin of high performance. This work highlights the potential of lead-free Ba_0.95Ca_0.05Ti_0.9Sn_0.1O₃/g-C₃N₄ Z-scheme heterojunctions as promising candidates to harvest the environmental mechanical vibration energy for piezocatalytic nitrogen fixation application in future.