Hierarchical cobalt phosphide hollow nanoboxes as high performance bifunctional electrocatalysts for overall water splitting

Developing earth-abundant and low-cost transition metal electrocatalysts for overall water splitting is crucial for renewable and sustainable energy technologies. Metal-organic frameworks (MOFs) are one of the most promising precursors for developing efficient and inexpensive catalysts with the large surface area and the abundant porosity. Herein, a new type of hierarchical CoP hollow nanoboxes (Cop NB) is fabricated for overall water splitting. Benefiting from the unique structural features including large specific surface area which can provides numerous active sites, abundant mass diffusion pathways, and the hierarchical and hollow structures, the as-synthesized CoP NB exhibit high activity and superior stability in alkaline media toward hydrogen and oxygen evolution reactions with low overpotentials of 101 mV and 240 mV, respectively, when the current density reaches 10 mA cm(-2). Remarkably, when a two-electrode water electrolyzer used CoP NB as both the anode and cathode, a low cell voltage of 1.58 V is sufficiently to afford 10 mA cm(-2). Moreover, this electrolyzer can be powered by a single AA battery, making the CoP NB an efficient bifunctional electrocatalyst for overall water splitting. Such good performance is attributed to the high intrinsic activity and superior structural stability. This work offers new prospects for the rational design and synthesis of efficient bifunctional electrocatalysts for application in electrochemical energy devices. (C) 2019 Elsevier Ltd. All rights reserved.