We report for the first time that CoSe with tetragonal metallic phase exhibits high electrocatalytic activity for hydrogen evolution reaction (HER) in acid solution. The prepared tetragonal CoSe exhibits an overpotential of 175 mV versus reversible hydrogen electrode at j = −10 mA cm⁻² and a notably low Tafel slope of 36.3 mV dec⁻¹, which are considerably superior to that of CoSe with a hexagonal metallic phase (352 mV and 104.6 mV dec⁻¹). Furthermore, by comparing the catalytic activity of both tetragonal and hexagonal phases of CoSe, our study reveals that the electrical conductivity still dominates on the basis that both phases are metallic. The catalytic activity of hexagonal CoSe can be improved by compounding single walled carbon nanotubes and achieve comparable performance with tetragonal CoSe. Combined with previous works that compare a semiconducting phase and a metallic phase, this work in addition deepens our understanding of the role of conductivity and phase structure in enhancing catalytic activity for HER electrocatalysts.

我们首次报道，具有四方金属相的CoSe对酸溶液中的析氢反应（HER）具有较高的电催化活性。相对于可逆的氢电极，制备的四方CoSe在j = -10 mA cm ^-2时具有175 mV的过电势，并且Tafel斜率非常低，为36.3 mV dec ^-1，这大大优于具有六方金属相的CoSe（ 352 mV和104.6 mV dec ^-1）。此外，通过比较CoSe的四方相和六方相的催化活性，我们的研究表明，在两相均为金属的基础上，电导率仍然占主导地位。六方CoSe的催化活性可以通过混合单壁碳纳米管来提高，并获得与四方CoSe相当的性能。与以前比较半导体相和金属相的工作相结合，这项工作还加深了我们对电导率和相结构在增强HER电催化剂催化活性中的作用的理解。