Bifunctional and durable MoSe2-RuSe2 heterojunction catalyst for alkaline seawater splitting

Abstract

Direct seawater electrolysis holds enormous potential for large-scale green hydrogen generation. However, chloride ions (Cl-) in seawater can cause catalyst corrosion and poisoning, reducing its efficiency and stability and posing considerable challenges to seawater electrolysis. Herein, we designed a highly efficient and corrosion-resistant MoSe2-RuSe2/NF heterojunction catalyst, which is in-situ grown as a reticular array on nickel foam (NF). Surface-aggregated molybdate and selenate ions could Cl- and blocks impurities in seawater, resulting in the excellent performance and corrosion resistance of MoSe2-RuSe2/NF heterojunction catalyst. In alkaline seawater, it shows low overpotentials of 50 mV and 242 mV at a current density of 10 mA cm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. And the overpotentials are only 339 mV for HER and 398 mV for OER even the current density rises to 500 mA cm-2. Moreover, a durability test at 500 mA cm-2 demonstrates that its stability exceeds 110 h. In a two-electrode seawater electrolysis system, it also delivers outstanding performance, achieving 100 mA cm-2 at a low voltage of merely 1.76 V, which is lower than that of the Pt/C||RuO2 benchmark catalyst (1.88 V). Theoretical calculations reveal that the heterojunction of MoSe2 and RuSe2 eliminates the band gap (0 eV) and boosts electronic occupancy. Benefiting from the unique heterogeneous interface, electron transfer in the catalyst is accelerated to enhance electrical conductivity, optimizes the d-band center in the electronic structure, and lowers the energy barriers, thereby promoting the adsorption/desorption kinetics of intermediates (H*, *OH, *O and *OOH). This work provides a novel heterojunction modulation strategy to design catalyst for efficiently producing hydrogen by splitting seawater.