Surface-Modified Hollow Ternary NiCo₂P_x Catalysts for Efficient Electrochemical Water Splitting and Energy Storage

Generally, a cost-effective electrocatalytic process that offers an efficient electrochemical energy conversion and storage necessitates a rational design and selection of structure as well as composition of active catalytic centers. Herein, we achieved an unprecedented surface morphology and shape tuning to obtain hollow NiCo₂P_x with a continuum of active sharp edges (spiked) on a hollow spherical surface by means of facile hydrothermal treatments. The highly exposed, branched spike-covered hollow structure of NiCo₂P_x shows remarkable performance enhancement for hydrogen evolution reaction and oxygen evolution reaction in a wide range of Ph solutions. This catalytic performance was utilized to assemble a water electrolyzer working in an alkaline environment. In particular, this electrolyzer only requires an output voltage of 1.62 V to deliver a current density of 10 mA cm^-2 and shows almost no decrease in this value even after a continuous run for 50 h. The new surface-engineered NiCo₂P_x establishes to be highly active, cost-effective, and robust toward electrochemical energy conversion. Additionally, the charge storage capabilities of spike-covered hollow NiCo₂P_x structures is also investigated, and it shows a specific capacitance of 682 and 608 F g^-1 at a current density of 1 A g^-1 with excellent rate capacitance retention. Thus, the importance of surface engineering of nanocrystalline morphologies in design toward the development of a multifunctional electrocatalyst for efficient water splitting and charge storage applications is demonstrated.