Nano-TiO2 anchored onto 2D Cu–Ni bimetallic MOF as a heterojunction for highly-efficient OER overpotential reduction.

The metal–organic framework (MOF) materials with large active sites and excellent catalytic properties have attracted widespread attention and are expected to be promising for oxygen evolution reaction (OER) for water splitting. Herein, we report a new and efficient heterogeneous nanostructure OER system constructed by a bimetallic 2D-layered porous metal–organic framework (Cu/Ni-MOF) and semiconductor nano-TiO2 particles. The bimetallic MOF can control its porous layered morphology by adjusting the ratio of surfactants. The OER performance of the hybrid system can be enhanced by introducing nano-TiO2 particles, and the performance of reducing the overpotential value is about 2.4 times higher than the pure Cu/Ni-MOF. Under illumination, the overpotential (η=10) is only 79 mV, which is much lower than the pure Cu/Ni-MOF (189 mV). At the same time, it can still maintain a low overpotential value of 168 mV after a 24 h stability test. This study also briefly tested the catalytic performance of the material in hydrogen evolution reaction (HER), and under the illumination conditions, the overpotential (η = 10) is 209 mV. Furthermore, it revealed the key role of bimetallic synergy and P–N heterojunction (via electrical and simulated photo-excited electrons) in boosting the OER performance of the system. The finding and proposed concept provide a new approach for synthesizing multi-metal MOFs and combining them with semiconductors to enhance the photoelectrochemical water splitting and open a new avenue to design high-performance MOF heterojunctions for photo-electrocatalysis. [ABSTRACT FROM AUTHOR]