A highly active and stable 3D dandelion spore-structured self-supporting Ir-based electrocatalyst for proton exchange membrane water electrolysis fabricated using structural reconstruction.

Summary To realize nonprecious‐metal catalysts with practical applicability for the hydrogen evolution reaction (HER), improved corrosion resistance and catalytic activity are required. In this study, composition‐controlled Co‐Cu alloys were fabricated by electrodeposition for use as HER catalysts in proton exchange membrane water electrolyzers (PEMWEs). As the Cu content in the alloy increased, the morphology changed from needle‐shaped particles to small round particles. Furthermore, a phase transition from a hexagonal close‐packed structure to a face‐centered cubic structure occurs because the latter structure is stabilized by adding Cu to Co. The optimum catalyst composition for the HER was found to be Co59Cu41, which had an overpotential of 342 mV at −10 mA cm−2. This catalyst exhibited excellent durability, showing a potential reduction of approximately 100 mV over 12 hours under a constant current density. This superior performance was attributed to the increase in the electrochemical surface area resulting from the addition of Cu, as confirmed by electrochemical double layer capacitance measurements, in addition to a counterbalance between the hydrogen adsorption energies of Co and Cu. Finally, the application of the Co‐Cu alloy catalyst as a cathode catalyst in a PEMWE resulted in excellent performance of 1.2 A cm−2 at 2.0 Vcell.

Summary The design of robust and high‐performance hydrogen evolution reaction (HER) catalysts is crucial for the scalable production of hydrogen by electrochemical water splitting. In this work, we fabricated hierarchically porous Co‐Ru catalysts with excellent catalytic activity and durability in acidic media. The morphology of the Co‐Ru catalysts was successfully controlled through an optimized electrochemical process. Among all Co‐Ru samples prepared in this study, the Co72Ru28 catalyst exhibited the largest catalytic surface area, as well as excellent HER activity (overpotential of 26.4 mV at −10 mA cm−2) and durability. X‐ray photoelectron spectroscopy measurements revealed the electron transfer between Co and Ru, indicating that the formation of the Co‐Ru alloy improved the activity and durability of the catalyst. Furthermore, a proton exchange membrane water electrolyzer (PEMWE) prepared with the Co72Ru28 sample showed excellent performances (3.4 A cm−2 at 2.0 Vcell), illustrating the promising potential of the present Co‐Ru catalysts as cathode materials for PEMWE systems.

Developing a non-precious or low Pt-group metal-containing (low-PGM) hydrogen oxidation reaction (HOR) catalyst is crucial to fabricate economic anion exchange membrane fuel cells (AEMFCs), an alternative to proton exchange membrane fuel cells (PEMFC). In this study, low-PGM Ni 100-x Rh x electrocatalysts, seldomly studied as alkaline HOR catalysts, with various compositions are fabricated via electrodeposition. Substantial changes are observed in both the morphology and crystalline structure of the catalysts when Ni is alloyed with Rh, such as enlarged surface area and development of different textures. The HOR activities of Ni 100-x Rh x catalysts evaluated in 0.1 M KOH solution are dramatically enhanced because of the enlarged surface area, bifunctional roles of H-providing sites (Ni/Rh) and OH-providing sites (Ni [OH] 2 /Rh 2 O 3), and their balanced composition on the surface. The durability of Ni 89 Rh 11 , the most appropriate catalyst, is investigated with the 3000 potential cycling, giving the average decay rate of approximately 0.30 μA cm −2 /cycle. The origin of enhanced activity and degradation during durability test was explained in terms of the electronic structures and surface composition of the catalysts. The initial high HOR activity of about 1.5 mA/cm 2 for Ni 89 Rh 11 at 0.05 V RHE , though it requires a further improvement in the durability, suggests the practical feasibility of it as a low PGM alkaline HOR catalyst.

No abstract