Defect-tailored ZnO nanoflowers enable efficient, metal-free ammonia synthesis through coupled piezoelectric and photocatalytic activation

ZnO–O V nanoflowers combine photo + piezocatalysis for bias-free N 2 reduction. Light + ultrasound drive charges to O V sites, boosting NH 3 with no hydrazine; 15 N verifies. DFT show stronger N 2 adsorption, lower *N 2 → *NNH barrier.