Fabrication of carbon nanotubes encapsulated cobalt phosphide on graphene: Cobalt promoted hydrogen evolution reaction performance

In the past a few decades, electro-catalytic hydrogen evolution reaction (HER) has been demonstrated to be an efficient method for production of clean hydrogen sources, and the central task is seeking for a low-cost and high-efficient catalyst. In this work, a carbon nanotubes (CNTs) encapsulated cobalt–cobalt phosphide on reduced graphene oxides material (Co–Co2P@CNT/rGO) was engineered via a simple high–temperature phosphating process. The as-gained catalyst was well-characterized, and we found that the metallic Co is essential to the formation of CNTs. Additionally, the catalyst was further employed in HER process. Compared with the metallic cobalt-free sample (Co2P@C/rGO), the Co–Co2P@CNT/rGO showed a significantly boosted HER activity with a Tafel slope of 55.43 mV dec−1 and an exchange current density of 5.62 × 10−3 mA cm−2. Besides, owing to the confining effect of CNTs, the Co–Co2P@CNT/rGO showed excellent stability during the 20 h stability test.