Synergy coupling of ternary CoNiFe-layered double hydroxides nanocages on CN-CNTs photoanodes for enhanced photoelectrochemical water oxidation

The pursuit of enhanced photoelectrochemical (PEC) water-splitting performance in carbon nitride (CN) photoanodes has led to numerous strategies due to its visible light responsiveness, affordability, and stability. Nonetheless, the rapid electron-hole recombination, poor conductivity, and sluggish surface reaction kinetics remain significant challenges for its applications. In this study, we successfully introduced ternary CoNiFe layered double hydroxide (LDH) nanocages onto carbon nanotubes (CNTs)-doped CN photoanodes. Improved crystallinity and accelerated charge transfer were achieved after CNTs doping for enhanced charge separation during the PEC reactions. Besides, the electronic band structure of CN/FTO photoanode was modulated for increased carrier concentration. The decoration of CoNiFe LDH nanocages not only provides more efficient reaction active sites but also accelerates the catalytic reaction kinetics for lower onset potential and improved PEC performance. The photocurrent density for CoNiFe-LDH/CN-CNTs/FTO photoanode increased around 4 times higher than that for the in-situ fabricated CN/FTO without any sacrificial agent in alkaline. The synergy corporation of LDH and CNTs brings more available holes with a longer lifetime and more active sites for water oxidation. This innovative approach establishes a new avenue for designing highly efficient water oxidation cocatalysts on semiconductor photoanodes, promising rational advancements in PEC applications.