ZnGa2-xAlxO4 (x = 0 ≤ 2) spinel for persistent light emission and HER/OER bi-functional catalysis

Bright and persistent green emitting MgGa2O4:Mn2+ for phosphor converted white light emitting diodes

Narrow band green emitting phosphors have gained widespread attention due to their application in white light emitting diode (wLED) backlight displays. Commercial backlight displays have a broad band green phosphor which limits their performance. In this work, bright, narrow and thermally stable green emitting MgGa2O4:Mn2+ (MGO-Mn) has been synthesized. Time-resolved emission spectroscopy suggested that Mn2+ ions are distributed at both Mg2+ and Ga3+ sites of the MGO spinel, which resulted in a high internal quantum efficiency of 63%. The colour purity of MGO-Mn (76.4%) superseded that of the commercial green phosphor β-SiAlON:Eu2+ (59.12%). Doping-induced creation of oxygen vacancies endows MGO-Mn with excellent persistent luminescence with a time duration of more than 900 s upon 4 min charging with 270 nm UV light and persistent radioluminescence of more than 6000 s when charged with X-rays for 1 min. Finally, tunable white LEDs (cool and neutral white LEDs) are fabricated by combining the RGB mixture of the green phosphor with commercial red and blue phosphors along with a 280 nm UV LED chip. This work also showcases the importance of different annealing atmospheres in the photoluminescence and persistent luminescence of the MGO-Mn phosphor.

Recent Advancements on Spin Engineering Strategies for Highly Efficient Electrocatalytic Oxygen Evolution Reactions

Oxygen evolution reaction (OER) is a widely employed half-electrode reaction in oxygen electrochemistry, in applications such as hydrogen evolution, carbon dioxide reduction, ammonia synthesis, and electrocatalytic hydrogenation. Unfortunately, its slow kinetics limits the commercialization of such applications. It is therefore highly imperative to develop highly robust electrocatalysts with high activity, long-term durability, and low noble-metal contents. Previously intensive efforts have been made to introduce the advancements on developing non-precious transition metal electrocatalysts and their OER mechanisms. Electronic structure tuning is one of the most effective and interesting ways to boost OER activity and spin angular momentum is an intrinsic property of the electron. Therefore, modulation on the spin states and the magnetic properties of the electrocatalyst enables the changes on energy associated with interacting electron clouds with radical absorbance, affecting the OER activity and stability. Given that few review efforts have been made on this topic, in this review, the-state-of-the-art research progress on spin-dependent effects in OER will be briefed. Spin engineering strategies, such as strain, crystal surface engineering, crystal doping, etc., will be introduced. The related mechanism for spin manipulation to boost OER activity will also be discussed. Finally, the challenges and prospects for the development of spin catalysis are presented. This review aims to highlight the significance of spin engineering in breaking the bottleneck of electrocatalysis and promoting the practical application of high-efficiency electrocatalysts.

Ruthenium-doped Ni(OH)2 to enhance the activity of methanol oxidation reaction and promote the efficiency of hydrogen production

The coupling of the hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR) to produce clean hydrogen energy with value-added chemicals has attracted substantial attention. However, achieving high selectivity for formate production in the MOR and high faradaic efficiency for H2 evolution remain significant challenges. In light of this, this study constructs an Ru/Ni(OH)2/NF catalyst on nickel foam (NF) and evaluates its electrochemical performance in the MOR and HER under alkaline conditions. The results indicate that the synergistic effect of Ni(OH)2 and Ru can promote the catalytic activity. At an overpotential of only 42 mV, the current density for the HER reaches 10 mA cm-2. Moreover, in a KOH solution containing 1 M methanol, a potential of only 1.36 V vs. RHE is required to achieve an MOR current density of 10 mA cm-2. Using Ru/Ni(OH)2/NF as a bifunctional catalyst, employed as both the anode and cathode, an MOR-coupled HER electrolysis cell can achieve a current density of 10 mA cm-2 with a voltage of only 1.45 V. Importantly, the faradaic efficiency (FE) for the hydrogen production at the cathode and formate (HCOO-) production at the anode approaches 100%. Therefore, this study holds significant practical implications for the development of methanol electro-oxidation for formate-coupled water electrolysis hydrogen production technology.