Cobalt oxide doped with titanium dioxide and embedded with carbon nanotubes and graphene-like nanosheets for efficient trifunctional electrocatalyst of hydrogen evolution, oxygen reduction, and oxygen evolution reaction

We synthesize a series of cobalt species combined with carbon nanotubes loaded onto graphene-like titanium carbide (CoOx-N-C/TiO2C), which are derived from bimetallic CoZn-based zeolitic imidazolite framework and Ti3C2Tx MXene composite (CoZn-ZIF/Ti3C2Tx). The as-result CoOx-N-C/TiO2C composites are further explored as the trifunctional electrocatalysts for hydrogen evolution reaction, oxygen reduction reaction, and oxygen evolution reaction. Among composites containing different Ti3C2Tx dosages, the CoOx-N-C/TiO2C(22.7%) exhibits the most excellent electrochemical conductivity. When CoOx-N-C/TiO2C(22.7%) is used as the electrocatalyst for water splitting, a current density of 10 mA cm(-2) (E-j = 10) is achieved at a low cell voltage of 1.45 V. Meanwhile, the overall oxygen activity of the CoOx-N-C/TiO2C(22.7%) shows a small potential difference (0.72V) between the E-j = 10 for oxygen evolution reaction and the half-wave potential for oxygen reduction reaction. The outstanding catalytic performances are mainly attributed to the synergistic effect among the different components of the CoOx-N-C/TiO2C composite, such as carbon nanotube content that is in favour of electronic mobility, hierarchical porosity that facilitates mass transport, and uniformly dispersed cobalt, cobalt oxide, and titanium dioxide active sites in the carbon framework. Consequently, the present work will shed light on the application of other metal-organic framework- and carbon-based electrocatalysts for energy conversion.