Double functionalization strategy toward Co-Fe-P hollow nanocubes for highly efficient overall water splitting with ultra-low cell voltage

Abstract

Due to their inherent structural and functional defects, most bifunctional catalysts usually delivered excellent electrocatalytic activities for one half-reaction at expense of the performances for another one, thus exhibiting inconspicuous electrocatalytic abilities for overall-water-splitting. In the present work, a novel strategy of controllable assembly and synergistic catalysis based on hydrogen evolution reaction (HER) active and oxygen evolution reaction (OER) active single functional sites, was ingeniously assembled to high-performance catalysts for overall-water-splitting. Monodispersed zeolitic imidazolate framework cubes were adopted as the reaction precursors to construct bi-functional electrocatalysts through conformal Prussian blue analogue layer coating and the subsequent thermal phosphorization process. HER active Co-P and OER active Co-Fe-P hetero-components were simultaneously anchored on the shell layers of the resulted Co-Fe-P hollow nanoboxes. Benefiting from the unique structural design and functional integration, the product catalyst afforded small overpotentials of 174 and 53 mV at 10 mA/cm2 for the OER and HER in alkaline media, respectively and a ultra-low operating cell voltage of 1.46 V for overall-water-splitting, superior to most recently reported striking bi-functional electrocatalysts. Moreover, its ultrastable catalytic activity was also impressive, delivering only negligible performance loss after a 24 h durability testing. More broadly, this combined double functionalization concept and nanoscale hollowing design is unique and advantageous, especially suitable for developing highly active and durable electrocatalysts of energy conversion reactions.