A standalone bismuth vanadate-silicon artificial leaf achieving 8.4% efficiency for hydrogen production

The development of scalable photoelectrochemical water splitting with high solar-to-hydrogen efficiency and long-term stability is essential while challenging for practical application. Here, we design a BiVO₄ photoanode with gradient distributed oxygen vacancies, which induces strong dipole fields to promote charge separation. Growing sea-urchin-like FeOOH cocatalyst on the photoanode leads to a photocurrent density of 7.0 mA cm^-2 at 1.23 V versus the reversible hydrogen electrode and is stable for over 520 h under AM 1.5 G illumination. By integrating with a silicon photovoltaic cell, the standalone artificial leaf achieves a solar-to-hydrogen efficiency of 8.4%. The scale-up of these artificial leaves up to 441 cm² in size can deliver a solar-to-hydrogen efficiency of 2.7% under natural sunlight. Life cycle assessment analysis shows that solar water splitting has little environmental footprint for hydrogen production. Our study demonstrates the possibility of designing metal oxide-based artificial leaves for scalable solar hydrogen production.