Recent Advances in Metal-Gas Batteries with Carbon-Based Nonprecious Metal Catalysts

Ru/Ir-Based Electrocatalysts for Oxygen Evolution Reaction in Acidic Conditions: From Mechanisms, Optimizations to Challenges

The generation of green hydrogen by water splitting is identified as a key strategic energy technology, and proton exchange membrane water electrolysis (PEMWE) is one of the desirable technologies for converting renewable energy sources into hydrogen. However, the harsh anode environment of PEMWE and the oxygen evolution reaction (OER) involving four-electron transfer result in a large overpotential, which limits the overall efficiency of hydrogen production, and thus efficient electrocatalysts are needed to overcome the high overpotential and slow kinetic process. In recent years, noble metal-based electrocatalysts (e.g., Ru/Ir-based metal/oxide electrocatalysts) have received much attention due to their unique catalytic properties, and have already become the dominant electrocatalysts for the acidic OER process and are applied in commercial PEMWE devices. However, these noble metal-based electrocatalysts still face the thorny problem of conflicting performance and cost. In this review, first, noble metal Ru/Ir-based OER electrocatalysts are briefly classified according to their forms of existence, and the OER catalytic mechanisms are outlined. Then, the focus is on summarizing the improvement strategies of Ru/Ir-based OER electrocatalysts with respect to their activity and stability over recent years. Finally, the challenges and development prospects of noble metal-based OER electrocatalysts are discussed.

Promoting the four electrocatalytic reactions of OER/ORR/HER/MOR using a multi-component metal sulfide heterostructure for zinc-air batteries and water-splitting

Multi-component metal sulfide heterostructures are promising for multi-functional catalytic activities. In this work, we fabricated a multi-component metal sulfide heterostructure (Co-S-INF, composed of Co3S4 and (Fe, Ni)9S8) with nanoflower morphology clustered with numerous nanosheets by the electrodeposition of cobalt on iron-nickel foam followed by hydrothermal sulfurization treatment. Co-S-INF possesses high multi-functional electrocatalytic properties toward the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and methanol oxidation reaction (MOR). In particular, the ORR potential at 10 mA cm-2 is 0.682 V, and the OER, HER, and MOR potentials at 100 mA cm-2 are 1.478 V, 0.289 V, and 1.417 V, respectively. By using Co-S-INF, the aqueous ZAB with an ultrahigh peak power density of 332.30 mW cm-2 and an overall water splitting (OWS) device with a low splitting voltage of 1.82 V at 100 mA cm-2 can be obtained. In addition, the OWS potential can be further decreased to 1.70 V at a current density of 100 mA cm-2 with the assistance of MOR at the anode accompanying the production of the high value-added formate. Our work opens the way for the application and development of multi-functional electrocatalysts.