Biomimetic 2D-Ni(Co,Fe)P/1D-WOx nanocoral reef electrocatalysts for efficient water splitting

Abstract

The design of efficient nanostructured electrocatalysts is highly desirable for promoting the hydrogen/oxygen evolution reactions (HER/OER), which are key processes of ecofriendly H₂ production in water splitting systems. In this study, we present novel biomimetic hierarchical nanocoral reef materials as efficient and durable electrocatalysts for alkaline water splitting. Our nanocoral reef catalyst has a unique structure consisting of Ni(Co,Fe)P nanosheet (NS) algae and WO_x nanowire (NW) corals. The WO_x NW corals effectively transport charges (e⁻/h⁺) to the Ni(Co,Fe)P NS algae through a 1D directional structure. The ultrathin 2D Ni(Co,Fe)P NS algae grown on the WO_x NW corals provide an abundance of active sites for splitting water molecules into H₂ and O₂. As a result, our hierarchical 2D-NS/1D-NW-structured NiCoP–WO_x (HER) and NiFeP–WO_x (OER) catalysts demonstrate excellent activities, requiring low overpotentials of 49 and 270 mV, respectively, to generate a current density of 10 mA cm⁻². Additionally, they exhibit high electrochemical stability for over 60 h in 1 M KOH. In addition, the overall water splitting (OWS) system, NiCoP–WO_x(HER)‖NiFeP–WO_x(OER) requires a cell voltage of 1.51 V to generate a current density of 10 mA cm⁻². This value is very low compared to other reported transition metal phosphides. The biomimetic engineering presented in the current study provides not only efficient electrocatalysts but also a promising, useful strategy to develop functional 1D/2D hierarchical materials for advanced energy applications.