Nickel–vanadium layered double hydroxide has recently been considered as a highly active, low-cost electrocatalyst and as a benchmark non-noble metal-based electrocatalyst for water oxidation. The material showed a current density of 27 mA/cm2 at an overpotential of 350 mV, which is comparable to the best-performing nickel–iron-layered double hydroxides for water oxidation in alkaline media. The enhanced conductivity and facile electron transfer were suggested among important factors for the high activity of nickel–vanadium layered double hydroxide. In the present study, the stability of an Ni–V catalyst was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and electrochemical characterization methods. These methods show that the initial Ni–V catalyst during water oxidation in alkaline conditions is converted from an initial α-Ni­(OH)2 phase to a partially oxidized α-Ni­(OH)2/NiOOH phase and VO4 3– ions. We carefully evaluate the stability of the catalysts and analyze the compositional changes during prolonged water-oxidation conditions using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The experiments using both Fe-free electrolyte and Fe-free nickel–vanadium layered double hydroxide reveal that vanadium do not affect the water-oxidizing activity of α-Ni­(OH)2.

Water splitting for hydrogen production has been recognized as a promising approach to store sustainable energy. The performance of this method is limited by the oxygen‐evolution reaction. Herein, an approach for synthesizing a highly active oxygen‐evolving catalyst by a one‐step, low‐cost, environmentally friendly, and easy‐to‐perform method is presented, which works by using iridium metal as the anode at a relatively high potential. The obtained IrOx/Ir interface showed an overpotential of 250 mV at 10 mA cm−2 in 0.1 m HClO4 and remained stable under electrochemical conditions. The IrOx that was mechanically separated from the surface of IrOx/Ir metal after operation showed a threefold increase in activity compared to the current benchmark IrO2 catalyst. Various characterization analyses were used to identify the structure and morphology of the catalyst, which suggested nanosized, porous, and amorphous IrOx on the surface of metallic Ir. This synthetic approach can inspire a variety of opportunities to design and synthesize efficient metal oxide‐based electrocatalysts for sustainable energy conversion and utilization.

No abstract

No abstract

Water-splitting for hydrogen production has been recognized as a promising approach for storage sustainable energy. To make this technology economically competitive, it is critical to find an efficient and scalable synthesis method to develop a robust water-oxidizing catalyst (WOC), since the performance of electrolyzers is limited by water-oxidation reaction (WOR). Herein, an approach to synthesis highly active WOC with a one-step, low-cost, environmentally friendly, and accessible method by operating metallic iridium as the anode electrode in a two-electrode system and at a relatively high potential is presented. The obtained IrOx shows an overpotential of only 250 mV at 10 mA.cm-2 in 0.1 M HClO4 and remains stable under electrochemical conditions. Various characterization analyses are used to identify the structure and morphology of synthesized iridium oxide/iridium, indicates that the final product is a porous amorphous IrOx/Ir interface. The synthesis method can inspire a variety of opportunities to design and synthesize efficient metal oxide-based electrocatalysts for sustainable energy conversion and utilization. Figure 1