Achieving Active and Stable Amorphous IrVOxOHy for Water Splitting

High-Performance Low-Iridium Catalyst for Water Oxidation: Breaking Long-Ranged Order of IrO2 by Neodymium Doping

Exploring efficacious low-Ir electrocatalysts for oxygen evolution reaction (OER) is crucial for large-scale application of proton exchange membrane water electrolysis (PEMWE). Herein, an efficient non-precious lanthanide-metal-doped IrO2 electrocatalyst is presented for OER catalysis by doping large-ionic-radius Nd into IrO2 crystal. The doped Nd breaks the long-ranged order structure by triggering the strain effect and thus inducing an atomic rearrangement of Nd─IrO2 involving the forming of Nd─O─Ir bonds along with an increased amount of oxygen vacancies (Ov), giving rise of a long-ranged disorder but a short-ranged order structure. The formed Nd─O─Ir bonds tailor the electronic structure of Ir, leading to a lowered d-band center that weakens intermediates absorption on Ir sites. Moreover, doping Nd triggers Nd─IrO2 to catalyze OER mainly through lattice oxygen mechanism (LOM) by activating lattice oxygen owing to abundant Ov. The optimal catalyst only requires a relatively low overpotential of 263 mV@10 mA cm-2 with a high mass activity of 216.98 A gIr -1 (at 1.53 V) (eightfold of commercial IrO2), and also shows a superior durability at 50 mA cm-2 (20 h) than commercial IrO2 (3 h) due to the oxidation-suppressing effect induced by Nd doping. This work offers insights into designing high-performance low-Ir electrocatalysts for PEMWE application.

Recent Advances in Iridium-based Electrocatalysts for Acidic Electrolyte Oxidation

Ongoing research to develop advanced electrocatalysts for the oxygen evolution reaction (OER) is needed to address demand for efficient energy conversion and carbon-free energy sources. In the OER process, acidic electrolytes have higher proton concentration and faster response than alkaline ones, but their harsh strongly acidic environment requires catalysts with greater corrosion and oxidation resistance. At present, iridium oxide (IrO2) with its strong stability and excellent catalytic performance is the catalyst of choice for the anode side of commercial PEM electrolysis cells. However, the scarcity and high cost of iridium (Ir) and the unsatisfactory activity of IrO2 hinder industrial scale application and the sustainable development of acidic OER catalytic technology. This highlights the importance of further research on acidic Ir-based OER catalysts. In this review, recent advances in Ir-based acidic OER electrocatalysts are summarized, including fundamental understanding of the acidic OER mechanism, recent insights into the stability of acidic OER catalysts, highly efficient Ir-based electrocatalysts, and common strategies for optimizing Ir-based catalysts. The future challenges and prospects of developing highly effective Ir-based catalysts are also discussed.

Robust PbO2 modified by co-deposition of ZrO2 nanoparticles for efficient degradation of ceftriaxone sodium

In recent years, PbO2 electrodes have received widespread attention due to their high oxygen evolution reaction (OER) activity. However, due to the brittle nature of the plating layer, it is easy to cause the active layer to fall off. Pb2+ will leach out with the electrochemical process causing secondary pollution. The starting point of this study is established to improve the stability and adhesion of the electrode coating. Electrochemical oxidation technology has the characteristics of high treatment efficiency, wide range of applications, and non-polluting environment. In this study, conventional PbO2 electrodes were modified by using co-deposition of ZrO2 nanoparticles. In addition, α-PbO2 was added to increase the stability of the electrodes. At a high current density of 1 A/cm2, the accelerated life of the pure PbO2 electrode is 648 h, the accelerated life of the PbO2-ZrO2 electrode is 1.37 times that of the pure PbO2, and the electrode with an added α-PbO2 layer is 1.69 times that of the pure PbO2 electrode. The amount of dissolved Pb2+ was only 29% of that of pure PbO2. The electrochemical performance of the electrode is evaluated by studying the degradation effect of ceftriaxone sodium (CXM). The addition of ZrO2 nanoparticles alters the particle size and deposition content of PbO2, leading to a unique crystal structure distinct from pure PbO2. Compared to conventional PbO2 electrodes, the PbO2-ZrO2 can remove chemical oxygen demand (COD) and pollutants more efficiently, removing for 59% increased by 38.47%. Therefore, PbO2-ZrO2 is of great value in the field of electrochemical degradation of industrial pollutants.

Rhenium Suppresses Iridium (IV) Oxide Crystallization and Enables Efficient, Stable Electrochemical Water Oxidation

IrO₂ as benchmark electrocatalyst for acidic oxygen evolution reaction (OER) suffers from its low activity and poor stability. Modulating the coordination environment of IrO₂ by chemical doping is a methodology to suppress Ir dissolution and tailor adsorption behavior of active oxygen intermediates on interfacial Ir sites. Herein, the Re-doped IrO₂ with low crystallinity is rationally designed as highly active and robust electrocatalysts for acidic OER. Theoretical calculations suggest that the similar ionic sizes of Ir and Re impart large spontaneous substitution energy and successfully incorporate Re into the IrO₂ lattice. Re-doped IrO₂ exhibits a much larger migration energy from IrO₂ surface (0.96 eV) than other dopants (Ni, Cu, and Zn), indicating strong confinement of Re within the IrO₂ lattice for suppressing Ir dissolution. The optimal catalysts (Re: 10 at%) exhibit a low overpotential of 255 mV at 10 mA cm^-2 and a high stability of 170 h for acidic OER. The comprehensive mechanism investigations demonstrate that the unique structural arrangement of the Ir active sites with Re-dopant imparts high performance of catalysts by minimizing Ir dissolution, facilitating *OH adsorption and *OOH deprotonation, and lowering kinetic barrier during OER. This study provides a methodology for designing highly-performed catalysts for energy conversion.