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Efficient and durable oxygen evolution reaction (OER) catalysts are highly required for the cost-effective generation of clean energy from water splitting. For the first time, an integrated OER electrode based on one-step direct growth of metallic iron-nickel sulfide nanosheets on FeNi alloy foils (denoted as FeNi S /FeNi) is reported, and the origin of the enhanced OER activity is uncovered in combination with theoretical and experimental studies. The obtained FeNi S /FeNi electrode exhibits highly catalytic activity and long-term stability toward OER in strong alkaline solution, with a low overpotential of 282 mV at 10 mA cm and a small Tafel slope of 54 mV dec . The excellent activity and satisfactory stability suggest that the as-made electrode provides an attractive alternative to noble metal-based catalysts. Combined with density functional theory calculations, exceptional OER performance of FeNi S /FeNi results from a combination of efficient electron transfer properties, more active sites, the suitable O evolution kinetics and energetics benefited from Fe doping. This work not only simply constructs an excellent electrode for water oxidation, but also provides a deep understanding of the underlying nature of the enhanced OER performance, which may serve as a guide to develop highly effective and integrated OER electrodes for water splitting.

Temperature-induced copolymers of poly(N,N-dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals (PDMAEMA-grafted CNC) were synthesized by surface-initiated atom transfer radical polymerization (ATRP). The graft copolymers were characterized by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). The size of the original CNC was 10-40 nm in width and 100-400 nm in length, as characterized by atomic force microscopy (AFM). The liquid-crystalline properties of the graft copolymers were investigated by using polarizing optical microscopy (POM). The graft copolymers exhibited fingerprint texture in lyotropic state. The temperature-induced fingerprint texture changes of PDMAEMA-grafted CNC aqueous suspensions were investigated at various temperatures. With increasing temperature, the spacing of the fingerprint lines decreases. Temperature-induced changes of PDMAEMA polymer chains result in changes of fingerprint texture.