Rational Design of Goethite-Sulfide Nanowire Heterojunctions for High Current Density Water Splitting

Thepreparation of efficient and stable bifunctionalelectrocatalystsfor electrochemical overall water splitting (OWS) to scale up commercialhydrogen production remains a great challenge. Here, we synthesizedheterojunction structures consisting of Co9S8/Ni3S2 nanowire arrays and amorphous goethite(FeOOH, & alpha;-phase) particles as efficient OWS catalysts usingan interface engineering strategy. The interfacial charge inhomogeneitycaused by the heterojunction contact leads to the generation of abuilt-in electric field, which makes the electron-deficient FeOOHand electron-rich Co9S8/Ni3S2 favorable for hydrogen/oxygen evolution reaction, respectively,thus ensuring the excellent activity of FeOOH/Co9S8/Ni3S2 as a bifunctional catalyst. FeOOH/Co9S8/Ni3S2 exhibits impressivecatalytic activity for the oxygen evolution reaction, achieving anultralarge current density of 1000 mA cm(-2) neededas low as 265 mV overpotential, and its stability was tested up to1440 h. Furthermore, an excellent OWS output (1.55 V to generate 10mA cm(-2)) is achieved by the bifunctional FeOOH/Co9S8/Ni3S2 catalysts.

Automated summary

We synthesized heterojunction structures of Co9S8/Ni3S2 nanowire arrays and amorphous goethite particles as efficient and stable bifunctional electrocatalysts for electrochemical overall water splitting. The interfacial charge inhomogeneity caused by the heterojunction contact generates a built-in electric field, favoring the hydrogen/oxygen evolution reactions. FeOOH/Co9S8/Ni3S2 exhibits impressive catalytic activity for the oxygen evolution reaction, achieving a large current density at low overpotential, and shows excellent stability for 1440 hours. Furthermore, the bifunctional FeOOH/Co9S8/Ni3S2 catalysts achieve an excellent OWS output.