Hierarchical CoP-FeP Branched Heterostructures for Highly Efficient Electrocatalytic Water Splitting

The development of efficient non-noble metal electrocatalysts for sustainable water splitting is crucial for clean energy conversion and has drawn extensive attention. Currently, nonprecious metal phosphides have emerged as efficient electrocatalysts to replace noble metals for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, it is still a great challenge for fabrication of universal, efficient and durable bifunctional electrocatalysts for these reactions via structural and component engineering. Herein, we report the design and construction of the hierarchical CoP-FeP branched heterostructures as high-performance and durable bifunctional electrocatalysts for both hydrogen and oxygen evolution electrocatalysis in various electrolytes. In such unique heterojunction, the intimate interfacial contact could induce built-in electric field at the interface, which effectively optimizes the surface electronic states of the FeP by the CoP, thus promoting the charge transfer and enhancing the electrocatalytic activity. As a consequence, the CoP FeP heterostructures exhibit excellent performance for HER electrocatalysis, needing overpotentials as low as 30 and 71 mV to drive the 10 mA cm(-2) current densities in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively, which are very close to that of Pt/C and rank it among the most HER-active electrocatalysts reported so far. Moreover, they can also behave as an efficient OER electrocatalyst with a very low overpotential of 250 mV at 10 mA cm(-2) in 1.0 M KOH, outperforming most of the nonprecious-metal phosphides previously reported.