Decorating Cu2O photocathode with noble-metal-free Al and NiS cocatalysts for efficient photoelectrochemical water splitting by light harvesting management and charge separation design

[Display omitted] •Cu2O photocathode decorated with noble-metal-free Al and NiS cocatalysts for PEC water splitting.•Al nanoparticles on the bottom acted as a plasmonic photosensitizer.•Al can increase light harvesting and generate hot electrons.•NiS nanoparticles on the surface can collect the electrons for facilitating charge separation.•Photocurrent density of Al/Cu2O/NiS is −5.16 mA/cm2, an eight-fold than that of pristine Cu2O. Developing low-cost but effective cocatalyst is of crucial importance for strongly enhancing the photoelectrodes performance in photoelectrochemical (PEC) water splitting. Herein, we firstly report a rational and low-cost design of a ternary photocathode that Cu2O sandwiched by spatial noble-metal-free cocatalysts (NiS nanoparticles on the surface and Al nanoparticles on the bottom) to realize enhanced PEC performance. The integration of Al with surface plasmon resonance (SPR) effect and electron trapper NiS spatially loaded on the Cu2O nanocubes is indeed conducive to excite the hot electron-hole pairs, boost the solar light absorption and elevate ultrafast spatial transfer and separation of photogenerated electrons and holes, resulting in remarkable photocurrent density of −5.16 mA/cm2 at 0 V vs. RHE, an eight-fold enhancement than that of pristine Cu2O. The selection of noble-metal-free Al and NiS cocatalysts is superior substitute to noble metal Au and Pt from the comparison with our previous work. Therefore, this work could inspire ongoing interest in the design of highly efficient and cost-effective hybrid photoelectrodes which is able to replace noble metals in practical applications of PEC water splitting.