Heterogeneous CoSe₂–CoO nanoparticles immobilized into N-doped carbon fibers for efficient overall water splitting

The rational construction of heterogeneous interface is considered as a promising approach to improve the electrocatalytic performance of non-noble metal materials. Herein, an electrospinning–pyrolysis–partial selenization strategy is proposed to construct the heterostructure nanoparticles of CoSe₂[sbnd]CoO, which are encapsulated into N-doped carbon fibers (CoSe₂[sbnd]CoO/NCF). The assembled CoSe₂[sbnd]CoO/NCF hybrid enables to integrate and optimize the multicomponent features from different components through electronic coupling effects. The heterojunction between CoO and CoSe₂ owns abundant nanointerface, which could induce the electron rearrangement to enhance the charge transfer ability and optimize the adsorption towards reaction intermediates. As a result, CoSe₂[sbnd]CoO/NCF presents superior cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) activities with low overpotentials, small Tafel slopes and robust durability. Impressively, the overpotentials to afford 10 mA cm⁻² current density for acidic HER, alkaline HER and OER upon CoSe₂[sbnd]CoO/NCF are 72, 117 and 279 mV, respectively, much lower than those counterparts. Further, the full water splitting device with CoSe₂[sbnd]CoO/NCF as both cathode and anode requires a low voltage of 1.604 V to attain 10 mA cm⁻². The current work proposes a new insight for interface engineering to improve the electrocatalytic performance of transition metal-based materials.