Natural light driven photovoltaic-electrolysis water splitting with 12.7% solar-to-hydrogen conversion efficiency using a two-electrode system grown with metal foam

Currently, photovoltaic-electrocatalytic (PV-EC) water splitting possesses the paramount solar-to-hydrogen energy conversion efficiency (STH) among various solar energy conversion and storage systems. However, three principal factors including noble metal-based electrodes, expensive photovoltaic cell, and concentrated solar light systems largely limited the large-scale practicable implementation of this strategy. In this work, CoNi layered-double-hydroxide (LDH) nanosheets arrays, CoFe2O4 nanoparticles and CoNi LDH/CoFe2O4 composite electrodes are controllably synthesized on Ni foam, Fe foam and NiFe alloy foam, respectively, via a facile hydrothermal process. Experiments and density-functional theory calculation results demonstrate that CoFe2O4 and CoFe2O4/CoNi LDH electrodes are suitable to be used as highly efficient, stable, and freestanding water-splitting electro anode and cathode, respectively. Significantly, combining with a commercial silicon-based solar cell, the assembled PV-EC water splitting device receives 12.7% STH under natural sunlight irradiation. This work provides a typical demonstration and valuable guidelines for practical large-scale solar-to-hydrogen generation using an inexpensive PV-EC technology. [Display omitted] •CoFe2O4 and CoNi LDH/CoFe2O4 composite electrodes are controllably prepared.•An efficient and stable two-electrode system for water-splitting is developed.•Natural light driven photovoltaic-electrolysis reaches 12.7% efficiency.•The active sites and electrolysis water splitting mechanism are determined.