NSRRC Activity Report 2022

062 NSRRC ACTIVITY REPORT 2022 on the performance of bimetallic electrocatalysts. As shown in Fig. 1 , the oxidation state of Co decreased during HER, but it remained greater than that of metallic Co(0), while the oxidation states and local structure of Ru remained largely unchanged, owing to the presence of underlying metallic Ru. To identify the potential-driven dynamic structures of Co sites, in situ extended X-ray absorption fine structure (EXAFS) spectra were recorded, as illustrated in Fig. 2 . The results showed that the P around Co sites was partially replaced by the Co–O moiety in alkaline electrolytes. Under the application of a cathodic potential, the Co( µ -O) 2 Ru moiety was also observed and identified as the active intermediate of electrocatalysts. Further analysis of the EXAFS results revealed that the reactive moiety was likely due to the varied interatomic distances of Co–Ru and Co–O paths and corresponding geometrical configuration around the Co and Ru sites. The atomic configuration of the Co( µ -O) 2 Ru moiety appeared to play a critical role in governing the resulting HER activity and the corresponding mechanism, with an anisotropic contraction of the Co( µ -O) 2 Ru moiety upon hydrogen evolution potentially leading to increased disorder of the surface moiety. Chen and his coworkers conducted another study and made a groundbreaking discovery. They successfully identified that a strong metal–support interaction could lead to the development of actual Fig. 2 : In situ Co K-edge EXAFS and corresponding wavelet spectra of (a) Ru–Ru 2 P@Co 0.6 and (b) Ru–Ru 2 P@Co 1.8 . [Reproduced from Ref. 1] Fig. 1 : In situ Co K-edge XANES spectra of the (a) Ru–Ru 2 P@Co 0.6 and (b) Ru–Ru 2 P@Co 1.8  samples during HER. [Reproduced from Ref. 1] electrocatalysts for the water-splitting reaction. They employed a series of operando XAS measurements to examine the nickel-vanadium layered double hydroxide (LDH) at SP 12B1 , 2 which was found to provide a strong metal-support interaction that was necessary to stabilize the single-atomic Ru reactive sites during both cathodic and anodic reactions. As shown in Figs. 3 and 4 , during the oxygen evolution reaction (OER), the oxidation state of Ni sites increased, while the oxidation state of Ru remained unchanged, indicating that, instead of the Ru sites, the Ni sites may act as the reactive site for electrocatalytic OER. However, during HER, the oxidation state of Ru slightly decreased, confirming that, rather than the Ni site, the Ru site was the reactive center in Ru/Ni 3 V-LDH. It was also found that the electrocatalyst was able to maintain its