Flexible, self-supported hexagonal β-Co(OH)2 nanosheet arrays as integrated electrode catalyzing oxygen evolution reaction

Designing highly efficient, earth abundant and robust electrocatalysts for oxygen evolution reaction (OER) plays a vital role during the development of various renewable energy storage and conversion devices, but still remains challenging. Using liquid metal as a mediator, herein we report a novel painting-alloying-dealloying strategy to synthesize flexible, self-supported hexagonal β-Co(OH)2 nanosheet arrays anchored on Co plates. Free of any binder/conducting agent, the integrated Co(OH)2/Co electrode exhibits superior electrocatalytic activity (merely 332 mV @ 10 mA cm−2) and stability (25 h with negligible degradation) towards OER in an alkaline solution, as benchmarked with the state-of-art Co-based catalysts. The enhanced performance of this electrode originates from the unique ultrathin (∼15 nm) nanosheet morphology (providing abundant active sites), the in-situ growth characteristic (improving the electronic conductivity) and the open array structure (accelerating the transfer of electrolyte and the release of gases). Thanks to the merit of liquid metal, both the pattern and shape of the integrated electrode can be facilely designed and regulated, without influencing the OER activity. Furthermore, using a separator between the anode and cathode, the integrated architecture of electrodes allows for the compact-type electrolyzer for overall water splitting.