A highly-stable and low-energy-barrier photoelectrocatalyst (NiFe-LDH@Ti-MOF) for water splitting at high current densities via breaking the atomic structure symmetry

Abstract

There is a flurry of interest in enhancing the stability and efficiency of photoelectrocatalysts in water splitting at high current densities. In the present study, nickel–iron layered double hydroxide (NiFe-LDH) was decorated with MIP-177-LT (Ti-metal organic framework (MOF)) to fabricate a heteroatom electrocatalyst (NiFe-LDH@Ti-MOF). The overpotentials of the oxygen evolution reaction (OER) turned out to be very low: 199 and 232 mV at current densities of 200 and 600 mA cm−2, in that order. Then, current densities of 1,000 mA cm−2 were applied to the modified electrode over a long period of 800 h, and this generated a higher stability than that of the commercial IrO2. Further, its mass activity proved ∼2 and 7 times as high as those of IrO2 and NiFe-LDH, in that order. Furthermore, for water splitting, the produced photoelectrocatalyst obtained a current density of 1,000 mA cm−2 using only 1.6 V, and this performance remained changeless for 800 h, which can be considered the most superb performance ever reported. The experimental characterization revealed that during the process of doping Ti-MOF on NiFe-LDH, symmetry breaking takes place in the atomic structure of the LDH surface, which increases the active sites in the photoelectrocatalyst. The presence of oxygen in the Ti-MOF active sites improves the efficiency of OER at high current densities and also contributes to the higher stability of multiple heteroatomic interfaces for water splitting. The propounded strategy enables the generation of oxygen and hydrogen from water splitting at high current densities on an industrial scale by changing the symmetry of the atomic structure of heteroatomic photocatalysts.