Highly purified dicobalt phosphide nanodendrites on exfoliated graphene: In situ synthesis and as robust bifunctional electrocatalysts for overall water splitting

Designing highly active, earth-abundant and robust electrocatalysts with large surface areas, abundant active sites, good electric conductivity, and minimization of gas bubble adhesion operated in the same electrolyte toward overall water splitting remains a grand challenge. Herein, we report an in situ synthesis of dendritic dicobalt phosphide (Co2P) nanostructures with high purity on exfoliated graphene (EG), denoted as Co2P/EG, which show superior performances toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The abundant active sites featured by dendritic nanostructures, and fast electron transfer kinetics of EG as well as synergistic effects between active species and substrate contribute to the improved catalytic performances for HER and OER. In specific, for the HER, the CO2P/EG shows excellent activity with a low overpotentials of 163 mV and 157 mV at 10 mA cm(-2) in 0.5 M H2SO4 and 1.0 M KOH, respectively. While for the OER, it also exhibits high efficiency with an overpotential of 260 mV at 10 mA cm(-2) in 1.0 M KOH. More impressively, a Co2P/EG parallel to Co2P/EG two-electrode alkaline electrolyzer affords a current density of 10 mA cm(-2) at a low cell voltage of 1.67 V, along with satisfied stability. An AA dry battery with a nominal voltage of 1.5 V can drive overall water splitting with obvious gas bubble release. Moreover, our synthetic approach might be applied for in situ synthesizing various metal phosphides/EG for electrolysis-based energy conversion. (C) 2019 Elsevier Ltd. All rights reserved.