Enhancement in the charge transport and photocorrosion stability of CuO photocathode: The synergistic effect of spatially separated dual-cocatalysts and p-n heterojunction

The low carrier mobility and poor photocorrosion stability severely restrict the application of cupric oxide (CuO) as a photocathode in photoelectrochemical (PEC) water splitting. To resolve the above issues, we have designed and synthesized a novel as well as highly efficient NiO/CuO/MoS2 composite photoelectrode for the first time. In the ternary NiO/CuO/MoS2 photoelectrode, the MoS2 cocatalyst (top layer) can not only act as an electron transport layer to drive photogenerated electrons to the electrode /electrolyte interface, but also can construct a p-n heterojunction with CuO to accelerate the transfer of photogenerated carriers and inhibit the recombination of electron-hole pairs. Meanwhile, the NiO cocatalyst (bottom layer) can serve as a hole-transfer layer to promote the transport of photoinduced holes to the substrate. This rational design of selectively integrating the electron and hole transport layers into the CuO photocathode effectively promotes spatial separation of photogenerated electrons and holes, and helps to improve the carrier mobility and the photocorrosion stability of CuO photocathode. On account of the synergistic effect of spatially separated dual-cocatalysts and p-n heterojunction, the fabricated NiO/CuO/MoS2 photoelectrode achieves a high photocurrent density of −2.14 mA/cm2 at −0.55 V vs. Ag/AgCl and photocorrosion stability of 94% after 2 h. This rational combination of dual-cocatalysts with photocathodes could provide stimulating perspectives to improve the PEC performance and photocorrosion stability of narrow-gap semiconductors.