Optimizing the electronic structure of NiSe2/CoSe2 nanosheet arrays by phosphorus doping for high-efficiency oxygen evolution electrocatalysts

Transition metal selenides with pyrite cubic phase structure have attracted much attention in the field of electrochemistry, for their low resistivity properties (<10−3 Ω cm) of Pauli paramagnetic metals. In view of the multi-step catalytic reaction in electrocatalytic oxygen evolution, NiSe2 and CoSe2 with the same crystallographic space group are selected to construct NiSe2/CoSe2 nanosheet arrays on carbon cloth by a facile layered double hydroxides (LDHs) selenization derived method. Moreover, the effect of phosphorus doping on electronic structure and electrocatalytic activity of NiSe2/CoSe2 is also investigated. When the mole ratio of phosphorus to selenium is 10%, the prepared phosphorus-doped NiSe2/CoSe2 nanosheet arrays (10%P-NiSe2/CoSe2) show superior oxygen evolution reaction (OER) performance in alkaline media. It exhibits a small overpotential of 287 mV to realize a current density of 50 mA cm−2 and a low Tafel slope of 68 mv dec−1 in 1 M KOH solution. Furthermore, the cyclic stability test displays that the current density of 10%P-NiSe2/CoSe2 only decreases from 30.0 to 26.5 mA cm−2, after 12 h of continuous water oxidation reaction at 270 mV overpotential. The excellent OER activity of 10%P-NiSe2/CoSe2 can be attributed to the changes in charge density on the crystal surface and the lattice distortion in crystal caused by phosphorus doping. Our work provides an efficient approach for designing OER electrocatalysts through a LDHs derivation assembling with an anion doping method.