The development of a high-performance electrocatalyst for oxygen evolution reaction (OER) is imperative but challenging. Here, a partial sulfidation route to construct Ni 2 Fe-LDH/FeNi 2 S 4 heterostructure on nickel foam (Ni 2 Fe-LDH/ FeNi 2 S 4 /NF) by adjusting the hydrothermal duration is reported. The heterostructures afford abundant hydroxide/sulfide interfaces that offer plentiful active sites, rapid charge and mass transfer, favorable adsorption energy to oxygenated species (OH − and OOH) evidenced by the density functional theory calculations, which synergistically boost the alkaline water oxidation. In the 1.0 m KOH solution, Ni 2 Fe-LDH/FeNi 2 S 4 /NF exhibits an excellent OER catalytic activity with a much smaller overpotential (240 mV) to reach the current density of 100 mA cm −2 than single-phase Ni 2 Fe-LDH/NF (279 mV) or FeNi 2 S 4 /NF (271 mV). More impressively, 2000 cycles of cyclic voltammetry scan for water oxidation results in the formation of a sulfate layer over the catalyst. The corresponding post-catalyst demonstrates better OER activity and durability than the initial one in the alkaline simulated seawater electrolyte. The post-Ni 2 Fe-LDH/FeNi 2 S 4 /NF delivers smaller overpotential (250 mV) at 100 mA cm −2 and longer stability time than the original form (260 mV). The post-formed sulfate passivating layer is responsible for the outstanding corrosion resistance of the salty-water oxidation anode since it can effectively repel chloride.

Compared to freshwater electrolysis, seawater electrolysis to produce hydrogen is preferable and more promising, but this technology is plagued by the electrode’s corrosion and oxidative reactions of the competitive Cl– ion on the anode. To develop efficient oxygen evolution reaction (OER) catalysts for seawater electrolysis, the ultrathin MnO x film-covered NiFe-layered double-hydroxide nanosheet array is directly assembled on Ni foam (MnO x /NiFe-LDH/NF) by hydrothermal and electrodeposition in turn. This catalyst demonstrates excellent OER-selective activity in alkaline saline electrolytes. In 1 M KOH/0.5 M NaCl and 1 M KOH/seawater electrolytes, MnO x /NiFe-LDH/NF exhibits lower overpotentials at 100 mA cm–2 (η100 values of 265 and 276 mV, respectively) and Tafel slopes (73 and 77 mV decade–1, respectively) than does the NiFe-LDH/NF electrode (η100 values of 298 and 327 mV and Tafel slopes of 91 and 140 mV decade–1, respectively). In alkaline saline solutions, the stability and durability of the former are also better than those of the latter. The good OER selectivity and catalytic performance are attributed to the MnO x overlayer that selectively blocks Cl– anions from approaching catalytic centers, and the good conductivity, fast kinetics, more oxygen vacancies, and abundant active sites of MnO x /NiFe-LDH/NF. The robust stability is due to the enhanced resistance for Cl– corrosion stemming from the MnO x protective film. Hence, MnO x /NiFe-LDH/NF can act as a promising OER electrocatalyst for alkalized natural seawater electrolysis.

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Rheumatoid arthritis (RA) is well-known as a kind of autoimmune disease, which brings unbearable pain to the patients by multiple organ complications besides arthritis. To date, RA can be hardly cured, but early diagnosis and standard treatment can relieve symptoms and pain. Therefore, an effective tool to assist the early diagnosis of RA deserves considerable attention. On account of the overexpressed ONOO– during the early stage of RA, a near-infrared (NIR) receptor, Lyso-Cy, is proposed in this work by linker chemistry to expand the conjugated rhodamine framework by cyanine groups. Contributed by the pH-sensitive spiral ring in rhodamine, receptor Lyso-Cy has been found to be workable in lysosomes specifically, which was confirmed by the pH-dependent spectra with a narrow responding region and a well-calculated pK a value of 5.81. We presented an excellent ratiometric sensing protocol for ONOO– in an acidic environment, which was also available for targeting ONOO– in lysosomes selectively. This innovative dual-targeting responsive design is expected to be promising for assisting RA diagnosis at an early stage with respect to the joint inflammatory model established in this work at the organism level.