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Developing highly efficient, stable, and inexpensive electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is the premise of achieving large-scale water splitting. Here, NixFe1−xB prepared by a facile borothermal reduction in molten salt is a robust bifunctional electrocatalyst for overall water splitting. The NixFe1−xB electrocatalyst achieves a current density of 10 mA cm−2 at overpotentials of 63.5 mV for the HER and 282 mV for the OER in 1 M KOH electrolyte, respectively. Density functional theory (DFT) calculations suggest that the NixFe1−xB possesses a lower absolute value of H* adsorption free energy (‖ΔGH*‖) than the primitive FeB and NiB, which is beneficial to improve the HER activity. Two identical NixFe1−xB electrodes are combined to form an alkaline electrolyzer, which achieves a current density of 10 mA cm−2 at 1.57 V for overall water splitting. This work provides a strategy to develop highly efficient transition metal boride catalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

Herein, we report the successful formation of graphitic carbon nitride coated titanium oxide nanotube array thin films (g-C3N4/TiO2) via the facile thermal treatment of anodized Ti sheets over melamine. The proportion of C3N4 and TiO2 in the composite can be adjusted by changing the initial addition mass of melamine. The as-prepared samples are characterized by several techniques in order to understand the morphological, structural, compositional and optical properties. UV-vis absorption studies exhibit a remarkable red shift for the g-C3N4/TiO2 thin films as compared to the pristine TiO2 nanotubes. Importantly, the prepared composites exhibit an enhanced photocurrent and photo-potential under both UV-vis and visible light irradiation. Moreover, the observed maximum photo-conversion efficiency of the prepared composites is 1.59 times higher than that of the pristine TiO2 nanotubes. The optical and electrochemical impedance spectra analysis reveals that the better photo-electrochemical performance of the g-C3N4/TiO2 nanotubes is mainly due to the wider light absorption and reduced impedance compared to the bare TiO2 nanotube electrode. The presented work demonstrates a facile and simple method to fabricate g-C3N4/TiO2 nanotubes and clearly revealed that the introduction of g-C3N4 is a new and innovative approach to improve the photocurrent and photo-potential efficiencies of TiO2. [ABSTRACT FROM AUTHOR]