energy conversion and storage. [1,2] Developing efficient electrocatalysts that can effectively enhance the sluggish kinetic processes are particularly important to the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at low overpotentials. [3,4] Platinum group metals and noble metal oxides (e.g., IrO 2 , RuO 2 ) are considered as pioneering HER and OER catalysts, respectively. However, the large-scale applications are limited by the scarcity and high cost of these materials. [5,6] Recently, a great deal of effort and progress has been made toward the development of earth-abundant, highly efficient, and durable HER and OER catalysts, such as transition metal chalcogenides, [7][8][9] phosphides, [10][11][12] nitrides, [13][14][15] and carbides [16][17][18] (for HER), and transition metal oxide, [19][20][21] hydroxide/oxyhydroxide, [22][23][24] phosphate, [25][26][27] and carbon materials [28][29][30] (for OER). Due to the thermodynamic convenience and practical application in proton-exchange membrane or alkaline electrolyzers, these HER and OER catalysts generally exhibit high activity in strongly acidic and basic conditions, separately; thus pairing the two type catalysts in an integrated electrolyzer with high efficiency and stability for overall water splitting is difficult due to the mismatch of electrolyte pH. [31,32] There is Developing efficient, durable, and earth-abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing largescale water splitting. The authors report that FeB 2 nanoparticles, prepared by a facile chemical reduction of Fe 2+ using LiBH 4 in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB 2 electrode delivers a current density of 10 mA cm −2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec −1 , respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron-rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen-containing intermediates, thus favoring the HER process. The excellent OER activity of FeB 2 is ascribed to the formation of a FeOOH/ FeB 2 heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB 2 -NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm −2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state-of-the-art Pt/C and RuO 2 /C.

A highly efficient bifunctional electrocatalyst of nickel–iron phosphates for hydrogen and oxygen evolution reactions (HER and OER) was designed and preparedviaa simple electrodeposition method.

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Bulk abundant Ti3+ self-doped TiO2 nanotube arrays are prepared by a microwave-assisted chemical reduction method with NaBH4.

The growth process and crystallizing mechanisms of anodic oxide films on highly pure titanium plates are studied in 0.1 M H 2 SO 4 solution at potentiostatic, potential-sweep and combined anodization modes with the same final voltage of 30 V. The influences of anodization mode on the crystalline behavior, surface morphology, chemical composition and electrochemical properties of titanium anodized films are studied. The results show that the potentiostatically grown film is thicker, rougher and more crystalline than the film formed at potential-sweep and combined modes. The titanium oxide film contains an outer porous layer and an inner barrier layer, and the barrier layer of the slow-grown film is much thicker than that of the fast-grown film. For titanium oxide film formed in the potentiostatic mode, "flower-like" crystalline grains are developed due to very high local current density at the local defect sites of titanium surface. In the case of potential-sweep and combined anodization modes, the crystallization of titanium oxide film is homogeneous, which is mainly caused by the internal compressive stresses.