When eutectic composites meet photoelectrochemistry – Highly stable and efficient UV–visible hybrid photoanodes

• The use of eutectic composite as PEC-cell photoanodes is demonstrated.
• TiO2 and WO3 are combined into one composite broadened absorption from UV to visible.
• Maximum photocurrent of 4.4 mA/cm2 for TiO2–WO3 eutectic photoanode was obtained.
• 3 μA/cm2 per minute photocurrent-density-degradation rate was achieved under 6 suns.

Hydrogen – a potentially promising alternative to fossil fuels – can be produced by using solar energy to drive water splitting in photoelectrochemical (PEC) cells. However, the commercialization of PEC cells is currently hampered by the low light-absorption efficiency and poor stability of conventional photoanode materials. Here, we describe the use of a eutectic composite to create a highly stable and efficient PEC cell photoanode that can split water. The eutectic photoanode was prepared using eutectic solidification to couple two photoactive phases with different band gaps – titanium dioxide (TiO2) and tungsten trioxide (WO3) – and thereby achieve efficient absorption across a relatively broad range of UV and visible light wavelengths. Our PEC cell yields a maximum photocurrent density of 4.4 mA/cm2 at 1.7 V with respect to the normal hydrogen electrode and demonstrates high stability over 3000 s under 6 suns of illumination. We present detailed measurements of the electrical properties of the electrodes. The use of hybrid eutectic composites with engineered absorption band gaps in PEC cells could open up a new route to highly efficient and stable photoanodes.

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