The development of low-cost, high-activity, durable non-precious metal bifunctional electrocatalysts is of great importance in the production of hydrogen by water electrolysis. In this work, we have prepared new Al-doped Ni₃S₂ nanosheet arrays grown on Ni foam (Al-Ni₃S₂/NF) as an excellent bifunctional electrocatalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The Al-Ni₃S₂/NF electrode obtained only requires extremely low overpotentials of 86 and 223 mV for the HER and OER to achieve a current density of 10 mA cm⁻² in 1 M KOH, respectively. Moreover, the electrolytic cell assembled using this electrode as both cathode and anode provides a current density of 10 mA cm⁻² at an extremely low battery voltage of 1.58 V relative to that with Ni₃S₂/NF (1.71 V). Additionally, both experimental results and theoretical calculations reveal that the increased electrochemical active surface area and optimized intermediate adsorption free energies are responsible for the enhanced electrocatalytic performance. This work provides a promising bifunctional electrocatalyst for water electrolysis in alkaline media with broad application prospects.

Based on analysis of the current–time curve and observation of surface morphology including top, cross-section, bottom and substrate views by scanning electron microscopy (SEM), a new growth, dissolution–breakdown model, of self-organized titania nanotube arrays is presented. By this model, many phenomena raised during anodization are explained, such as the sharp decrease of current in initial period, current transient, occurring of ridges on tube walls, and formation of not pores but tubes etc. Furthermore, the reason for the occurrence of a porous structure, the balance between internal energy and surface energy, was proposed too. This study may also shed light on the formation of porous oxide films on other valve metals.

Mn-doped TiO₂ micro/nanostructure porous film was prepared by anodizing a Ti-Mn alloy. The film annealed at 300 °C yields the highest areal capacitance of 1451.3 mF/cm² at a current density of 3 mA/cm² when used as a high-performance supercapacitor electrode. Areal capacitance retention is 63.7% when the current density increases from 3 to 20 mA/cm² and the capacitance retention is 88.1% after 5,000 cycles. The superior areal capacitance of the porous film is derived from the brush-like metal substrate, which could greatly increase the contact area, improve the charge transport ability at the oxide layer/metal substrate interface and thereby significantly enhance the electrochemical activities toward high performance energy storage. Additionally, the effects of manganese content and specific surface area of the porous film on the supercapacitive performance were also investigated in this work.