Enhancing the electrochemical hydrogen evolution of CoP3/CoMoP nanosheets through the support of black TiO2−x nanotube arrays

The hydrogen evolution reaction (HER) is a crucial part of renewable energy application. It is still a huge challenge to enhance the intrinsically catalytic performance of non-noble metal-based electrocatalysts. Transition metal phosphides (TMPs) have been recognized as the effective HER catalysts. However, TMPs nanosheets suffer from low activity for water dissociation, which prohibits the HER properties of electrocatalyst in alkaline solution. Herein, a structure that decorates CoP3/CoMoP nanosheets on the black TiO2−x nanotube arrays substrate has been designed. The oxygen vacancy in the black TiO2−x substrate is expected to play an important role in the water dissociation and therefore enhance the initial Volmer step during HER. What’s more, the nanotube structure of black TiO2−x substrate provides a larger surface area for CoP3/CoMoP nano sheets decoration, the number of active sites enhanced during the reaction, resulting in higher HER performance. Experimental results demonstrate that CoP3/CoMoP/TiO2−x@Ti possesses much improved HER properties with a low overpotential of 143 mV at 10 mA−2 and a Tafel slope of 61 mV dec−1, it also provides long-term durability without significant degradation for 48 h. This work develops a low-cost and valuable approach to enhance the HER activity of transition metal phosphides in alkaline electrolytes.