Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiency and green hydrogen production through electrochemical water splitting. Currently, iron-doped nickel-LDHs (NF-LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemical synergetic effects between Ni and Fe. Here, the third element addition into NF-LDHs is designed to further enhance the electrocatalytic performance through the modulation of electronic property. Cu-doped NF-LDHs (NFC-LDHs) are developed with the selfsupported structure on porous supports. NFC-LDHs can be grown on carbon cloth (CC) in an intriguing 2D nanosheet structure, wherein the surface electronic configuration is suitably modulated by interactions among Ni-Fe-Cu. Importantly, activation energy for OER can be lowered by adding Cu into NF-LDHs. Thereby, the NFC-LDHs exhibited enhanced OER activity and improved stability than those of nickel-LDHs (Ni-LDHs) and NF-LDHs. For NFC-LDHs, small overpotentials of only 230 and 250 mV yield current densities of 50 and 100 mA cm À2 , respectively. In addition, excellent electrochemical stability is demonstrated during long-term OER tests without any degradation demonstrating no dissolution of active metals water electrolysis due to synergetic effects among Ni-Fe-Cu.

Transition metal chalcogenides have been widely studied as a promising electrocatalyst for the hydrogen evolution reaction (HER) in acidic conditions. Among various transition metal chalcogenides, tungsten disulfide (WS2) is a distinguishable candidate due to abundant active sites and good electrical properties. Herein, we report a facile and selective synthetic method to synthesize WS2 with an intriguing two-dimensional nanostructure by using cysteine (C3H7NO2S) as a chemical agent. In addition, nitrogen can be incorporated during chemical synthesis from cysteine, which may be helpful for enhancing the HER. The electrocatalytic activity of N-doped WS2 exhibits a promising HER in acidic conditions, which are not only higher than W18O49 nanowires and hex-WO3 nanowires, but also comparable to the benchmark Pt/C. Moreover, excellent electrocatalytic stability is also demonstrated for acidic HER during long-term tests, thus highlighting its potential use of practical applications as an electrolyzer.

Electronic band structure of bismuth ferrite (BFO) is studied by computational and experimental methods.Bandgap of BFO is precisely determined using optical absorption spectra as well as density functional calculation (DFT). Both methods give a comparable result that BFO can have both of direct or indirect (very close to direct) bandgap of about 2.0~2.2 eV. Furthermore, electronic transition in BFO occurs via the unoccupied O 2p to the occupied Fe 3d states or the d-d transition in Fe 3d states. Intriguing electronic structure of BFO, a narrow bandgap and a multiple electronic transition route, render it as a promising candidate for a visible light photocatalyst.