Atomic engineering of trace endogenous Fe within natural clays into a self-supported Fe₁–P single-atom cocatalyst for photocatalytic hydrogen evolution

Mass and cost-effective synthesis of active and stable single-atom cocatalysts is vital for the development of efficient photocatalysts for sustainable H₂ evolution from water splitting but remains challenging. In this work, we report on the atomic engineering of trace endogenous Fe within the lattice of natural halloysite nanotubes (HNTs) to fabricate a self-supported Fe₁-P single-atom cocatalyst (Fe₁-P/HNTs) <i>via</i> a facile low-temperature phosphidation method without using external high-purity metal precursors and supports. As a result of the formation of abundant Fe₁-P active sites and the strong self-confinement effect of HNTs, the as-synthesized Fe₁-P/HNTs cocatalyst exhibits high H₂ evolution activity and stability in dye-sensitized systems under visible light. More significantly, the Fe₁-P/HNTs cocatalyst can also efficiently catalyze H₂ evolution when coupled with semiconductor photocatalysts (TiO₂, g-C₃N₄, and CdS), showing its excellent versatility under different application scenarios. This work provides a new strategy for the development of cost-effective single-atom cocatalysts by upgrading endogenous metal species within abundant natural resources for sustainable solar H₂ evolution.