Self-Reconstructed Amorphous CoO_x/NiCoB Heterostructure Catalysts for Enhanced HER Performance

Amorphous electrocatalysts exhibit potentials as precursors for triggering the in situ reconstruction to generate the real catalytic active species toward electrochemical processes. In this work, a new kind of amorphous Ni-Co-B alloy pre-catalysts for hydrogen evolution reaction (HER) is reported, which is obtained via a facile electroless plating strategy on the nickel foam (NF). Interestingly, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and morphological characterizations identify the in situ reconstruction process during HER accompanied by the preferential leaching of surface B species and the formation of amorphous CoO_x nanosheet arrays as the real active sites. Benefiting from the synergistic effect between the surface CoO_x layer and the inner unaltered NiCoB phase, the resultant CoO_x/NiCoB heterostructure catalyst achieves a low overpotential of 209 mV at the elevated current density of 500 mA cm^-2 and maintains stability for 300 h without significant attenuation. Theoretical calculation reveals the electron reconfiguration at the interfaces between the newly formed CoO_x and inner NiCoB phases, which is favorable for the stabilization of reconstructed active oxide layers at the reductive potentials for catalyzing HER. Moreover, the CoO_x/NiCoB heterostructure optimizes hydrogen adsorption free energies, thereby enhancing HER catalytic activity.