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

Abstract

The preparation of efficient and stable bifunctional electrocatalysts for electrochemical overall water splitting (OWS) to scale up commercial hydrogen production remains a great challenge. Here, we synthesized heterojunction structures consisting of Co9S8/Ni3S2 nanowire arrays and amorphous goethite (FeOOH, α-phase) particles as efficient OWS catalysts using an interface engineering strategy. The interfacial charge inhomogeneity caused by the heterojunction contact leads to the generation of a built-in electric field, which makes the electron-deficient FeOOH and 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 impressive catalytic activity for the oxygen evolution reaction, achieving an ultralarge current density of 1000 mA cm–2 needed as low as 265 mV overpotential, and its stability was tested up to 1440 h. Furthermore, an excellent OWS output (1.55 V to generate 10 mA cm–2) is achieved by the bifunctional FeOOH/Co9S8/Ni3S2 catalysts.

Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies

“…The current energy demand around the globe has intensified the research for clean and renewable energy technologies that can directly abate the continuous deterioration of the environment by achieving zero CO 2 emissions. − In this context, the utilization of solar energy for photocatalysis and photoelectrochemical (PEC) water splitting has attracted an extensive amount of research interest. − In recent times, scientists have focused on photoactive metal oxides as emerging materials owing to their low cost, facile synthesis, and long-term stability. − In the past few years, there has been an enormous amount of interest in the development of heterojunction-based composite materials, with enhanced photoactivity and redox ability. , It has been reported that the selection of materials for heterojunction formation based on their respective band edge positions is crucial to achieve favorable charge carrier dynamics. , In a typical PEC system, the hydrogen evolution reaction (HER) occurs at the photocathode [H + /H 2 at 0 V vs the reversible hydrogen electrode (RHE)], while the photoanode is responsible for the oxygen evolution reaction (OER, O 2 /H 2 O at 1.23 V vs the RHE) . Both photocatalysis and PEC water splitting involve the generation of electrons and holes under light, followed by their transport to the surface.…”

“… 10 − 12 In the past few years, there has been an enormous amount of interest in the development of heterojunction-based composite materials, with enhanced photoactivity and redox ability. 13 , 14 It has been reported that the selection of materials for heterojunction formation based on their respective band edge positions is crucial to achieve favorable charge carrier dynamics. 15 , 16 In a typical PEC system, the hydrogen evolution reaction (HER) occurs at the photocathode [H + /H 2 at 0 V vs the reversible hydrogen electrode (RHE)], while the photoanode is responsible for the oxygen evolution reaction (OER, O 2 /H 2 O at 1.23 V vs the RHE).…”