Here, we report a facile synthetic methodology to prepare uniform single crystalline CeO₂ nanotubes through a hydrothermal transformation of CeO₂ nanorods in aqueous Ce(NO₃)₃ solution. A chemically driven etching-dissolution-deposition mechanism is proposed, involving the surface Ce³⁺ hydrolysis and dissolution at tips of nanorods and subsequent redeposition and crystallization on the outer sides of nanorods. Compared to CeO₂ nanorods, CeO₂ nanotubes exhibited the richer structural defects, higher reducibility and larger surface area, leading to a higher haloperoxidase-like activity.

The strategy of element substitution is an effective way to tune the electronic structures of the active sites in catalysts, thereby leading to improvements in both the catalytic activity and stability. Herein, we design and synthesize pyrite-type nickel/phosphorus co-doped CoS₂ nanowires on carbon cloth (NiCoPS/CC) as efficient and durable electrodes for water electrolysis. Introduction of nickel and phosphorus produced stepwise and superb enhancement of the performance of the electrodes in the hydrogen evolution reaction due to regulation of the electronic structures of the active sites of the catalyst and accelerated charge transfer over a wide pH range (0-14). The NiCoPS/CC electrodes also delivered a nearly undecayed catalytic current density of 10 mA·cm^-2 at a low overpotential of 230 mV for oxygen evolution due to in situ formation of surficial Ni-Co oxo/hydroxide in 1.0 M KOH. Thus, the NiCoPS/CC electrodes gave rise to a catalytic current density of 10 mA·cm^-2 for overall water splitting at potentials as low as 1.54 V during operation over 100 h in 1.0 M KOH with a Faradic efficiency of ~100%.