Interfacial engineering of hierarchical MoNi4/NiO heterostructure nanosheet arrays as bifunctional electrocatalysts for urea-assisted energy-saving hydrogen production

Employing urea oxidation reaction (UOR) to substitute slow oxygen evolution reaction (OER) is an effective technique to accomplish high-efficiency hydrogen production. The exploitation of inexpensive and highly active bifunctional catalyst still remains a considerable challenge. We report the hybrid nanosheet arrays constructed of MoNi4/NiO heterojunction with hierarchically crosslinked network architecture by hydrothermal reaction and subsequent annealing process under H2/Ar atmosphere. The special heterostructure with neoteric morphology can promote electron shift and interface interaction through the powerful coupling interface between MoNi4 and NiO, increasing charge transfer speed, intrinsic activity and electrolyte transport. Only 31 mV overpotential and 1.37 V potential are needed to arrive 10 mA cm-2 for hydrogen evolution reaction (HER) and UOR, respectively. For the two-electrode urea-assisted electrolyzer, the lower potential of 1.41 V is required to reach 10 mA cm-2. Moreover, it displays superior stability with unceasing working for 54 h at the cell voltage of 1.41 V without obvious activity degeneration. This research provides an insight on the construct of high-efficiently bifunctional catalyst by synergistic coupling of NiMo-based alloys with metal oxides.