Interfacial engineering of the NiSe2/FeSe2 p-p heterojunction for promoting oxygen evolution reaction and electrocatalytic urea oxidation

The NiSe2/FeSe2 p-p heterojunction with built-in electric-field effects is constructed by a facile selenization strategy and shows superior electrocatalytic activity towards oxygen evolution reaction (OER) and urea oxidation reaction (UOR). [Display omitted] •The NiSe2/FeSe2 p-p heterojunction is constructed by a simple selenization strategy.•The obtained p-p heterojunction has strong electronic interactions and spontaneously constructs a built-in electric field at the heterointerface.•The designed NiSe2/FeSe2 p-p heterojunction exhibits superior OER and UOR performance. Heterogeneous electrocatalysis usually involves the charge transfer between the surface of electrocatalysts and corresponding reactants. Thus, modulating the surface electron density of electrocatalysts is an effective strategy to boost the electrocatalytic activity of targeted reactions. Herein, the NiSe2/FeSe2 p-p heterojunction is constructed via a simple selenization method for both oxygen evolution reaction (OER) and urea oxidation reaction (UOR). The designed NiSe2/FeSe2 electrocatalyst exhibits a superior activity towards OER, which only requires a low overpotential of 256 mV to reach a current density of 10 mA cm−2, and surpasses other selenides and even the state-of-the-art RuO2. Impressively, when employed as the UOR electrode, the NiSe2/FeSe2 heterojunction needs only 127 mV overpotential at 50 mA cm-2, remarkably superior to other selenides and confirming the less energy consumption for UOR. The comprehensive analysis demonstrates that the well-designed built-in electric field at the heterointerface of NiSe2/FeSe2 p-p heterojunction due to the difference of energy levels can expedite the charge transfer and thus strengthen the conductivity of heterojunction electrocatalyst. Moreover, the self-driven electron transfer across the NiSe2/FeSe2 heterointerface can induce local charge redistribution at the interface region, which is beneficial for the adsorption of OH− and urea owing to the electrostatic interaction. Therefore, the designed NiSe2/FeSe2 p-p heterojunction with regulated electronic structure displays extraordinary electrocatalytic activity for both the OER and UOR. This study demonstrates a novel strategy to manipulate the surface/interface charge states of electrocatalysts for improving the catalytic activity of OER and UOR, and provides new guidelines for exploring other superior electrocatalysts.