Electron-donating carbon dots decorating CuBi2O4 for efficient and stable photoelectrochemical seawater splitting

Electrode materials are pivotal to advancing the deployment of photoelectrochemical (PEC) seawater splitting. Carbon materials hold great potential for modifying semiconductors to fabricate high-performance photocathodes, but are limited in seawater by the Ca 2+ and Mg 2+ . Herein, a microwave-synthesized carbon dots ( m -CDs) were demonstrated as electron donors in composite photocathode materials to enhance their performance for seawater splitting. The as-prepared m -CDs/CuBi 2 O 4 photocathode exhibited a photocurrent density of 0.183 mA cm −2 at 0.4 V vs. RHE in simulated seawater, which was outperforming the pristine CuBi 2 O 4 (0.102 mA cm −2 ) and hydrothermal-synthesized carbon dots (h-CDs) modified CuBi 2 O 4 (0.106 mA cm −2 ) samples. The structural characterization results show that the surface of m -CDs is rich in acidic groups. These functional groups will significantly increase the H + concentration on the catalyst surface during the HER process, inhibit the rise of surface pH, thereby preventing Ca 2+ /Mg 2+ from forming hydroxides and reducing the catalytic performance. This study not only presents a metal-free carbon material to enhance the photocathode performance for seawater splitting, but also offers a theoretical foundation for the rational design of carbon materials in this field.