Unique sandwich-cookie-like nanosheet array heterojunction bifunctional electrocatalyst towards efficient overall water/seawater splitting

Construction of multi-component heterostructures is an effective strategy for electrocatalysts to improve both the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) activity at the anode. Herein, an efficient bifunctional electrocatalyst towards overall water/seawater splitting (OW/SS) is reported with strategy of heterostructure construction (ruthenium/nickel phosphorus) on nickel hydroxide (Ni(OH)2). With the unique hydrolysis layer (Ni(OH)2), the processes of H2O hydrolysis and the adsorption/desorption of H*/O-containing intermediates (OH, O, OOH) were greatly boosted by Ru and P sites, which acted as the catalytic active centers of OER and HER, respectively. In addition, the electronic structure reconfiguration was realized through the strong interaction between multi-interfaces. For alkaline HER at the current density of 10 mA cm−2, the overpotential of Ru-P-Ni(OH)2/NF (denoted as RNPOH/NF) was 98 mV, whereas just 230 mV of overpotential was essential to stimulate alkaline OER at the current density of 20 mA cm−2. Specifically, as a bifunctional electrocatalyst towards overall water splitting, RNPOH/NF deserves cell voltages of 1.7/1.92 V and 1.75/1.94 V, respectively, to activate current densities of 50/100 mA cm−2 in alkaline water/seawater systems, together with a good durability of 12 h. This work contributes insights to the development of bifunctional electrocatalysts for overall water/seawater splitting.