<p>Bias-free photoelectrochemical devices provide a sustainable route for solar hydrogen production from alkaline seawater, however, the requirement for large potential for anodic oxygen evolution and undesired chloride oxidation in seawater limit their efficiency. By leveraging the low oxidation potential of hydrazine, a toxic pollutant, bias-free devices can achieve high-performance hydrogen production and simultaneous degradation of hydrazine, effectively avoiding chloride oxidation. Here, we design a self-powered artificial leaf device, comprising a perovskite photocathode integrated with a noble-metal-free oxide catalyst for direct solar hydrogen production and hydrazine oxidation. The device exhibits a high photocurrent density of 25 mA cm^–2 and stability for 3 days under 1-sun illumination. Upscaling the artificial leaf device enables near-complete hydrazine degradation to below 1 ppb within ≈ 30 h under zero-bias operation. This study provides a scalable and sustainable approach for simultaneous hydrogen generation and pollutant removal, advancing the use of solar energy in environmental applications.</p>