Metal–Organic Framework Derived Narrow Bandgap Cobalt Carbide Sensitized Titanium Dioxide Nanocage for Superior Photo‐Electrochemical Water Oxidation Performance

Abstract

AbstractDespite recent progress in photo‐electrochemical (PEC) water oxidation systems for TiO2‐based photoanodes, PEC performance improvement is still seriously hampered due to poor carrier transport efficiency and sluggish surface water oxidation kinetics of pristine TiO2. Herein, for the first time a brand new metal–organic framework (MOF)‐derived Co3C nanosheet with narrow bandgap energy is demonstrated, to effectively sensitize TiO2 hollow cages as a heterostructure photoanode for PEC water oxidation. It is found that MOF‐derived Co3C nanosheet with narrow bandgap characteristic can simultaneously accelerate the surface water oxidation kinetics and extend the light harvesting range of pristine TiO2. Meanwhile, a uniquely matched type‐II heterojunction constructed between MOF‐derived Co3C and TiO2 results in an evidently spontaneous e−/h+ separation. MOF‐derived Co3C/TiO2 heterostructure photoanodes bring about drastically improved PEC water oxidation performance. Specifically, MOF‐derived Co3C‐3/TiO2 photoanode with an optimized content of Co3C achieves the highest photocurrent density and charge separation efficiency of 2.6 mA cm−2 and 92.6% at 1.23 V versus reversible hydrogen electrode, corresponding to 201% and 152% improvement compared with pristine TiO2 nanocages. The ingeniously prepared MOF‐derived Co3C carbide with narrow bandgap energy as a cocatalyst paves new way to construct potentially high performance solar‐energy conversion system.