Multiphase nanosheet-nanowire cerium oxide and nickel-cobalt phosphide for highly-efficient electrocatalytic overall water splitting

Herein, a hybrid nanowire-nanosheet structure made of the cerium oxide and nickel-cobalt phosphide (CeO2-NiCoPx) compound is in situ engineered on the Ni-Co foam (CeO2-NiCoPx/NCF) for the robust water splitting (HER and OER), and the overpotentials of synthesized CeO2-NiCoPx/NCF are about 39 mV for HER and 260 mV for OER at a current density of 10 mA cm−2 (j10). Meanwhile, the nanostructure of CeO2-NiCoPx is well preserved after a long-term electrocatalytic process (100 h) at a large current density of 100 mA cm−2 (j100). When the CeO2-NiCoPx/NCF simultaneously acts as the HER and OER electrodes, the potential of 1.49 V is obtained for transferring j10 with an excellent durability. Theoretical simulations and in operando Raman spectroscopy reveal that the Co and Ni atoms for CeO2-NiCoPx/NCF catalyst are likely to act as the pivotal reaction centers for HER and OER processes, respectively. CeO2-NiCoPx, a hybrid structure made of nanosheets and nanowires, is synthesized in situ on Ni-Co foam (NCF) as an efficient bi-functional electrocatalyst for water splitting. The CeO2-NiCoPx/NCF catalyst exhibits excellent catalytic activity, stability and sustainability, as well as very high H2/O2 yield for both HER and OER at industry-relevant current densities. The high catalytic activity is confirmed by the low overpotentials of 39 and 205 mV for HER, and 260 and 455 mV for OER at j10 and j500 in alkaline medium, respectively, as well as with the small Tafel slope of 67 (HER) and 72 (OER) mV dec−1. Moreover, the stability and sustainability over 100 h at j100 is achieved. [Display omitted] •High-performance, noble-metal-free bi-functional electrocatalyst for water splitting.•In situ synthesis of multiphase Ni-Co-Ce phosphide catalyst on Ni-Co electrolyzer electrode.•Heterointerfaces between CeO2 and NiCo phosphide expose rich catalytically active sites.•Remarkable electrocatalytic performance at industry-relevant current densities.•In operando Raman confirms active intermediate species on catalyst during HER and OER.