The surface reconstruction behavior of transition metal phosphides precursors is considered as an important method to prepare efficient oxygen evolution catalysts, but there are still significant challenges in guiding catalyst design at the atomic scale. Here, the CoP nanowire with excellent water splitting performance and stability is used as a catalytic model to study the reconstruction process. Obvious double redox signals and valence evolution behavior of the Co site are observed, corresponding to Co²⁺/Co³⁺ and Co³⁺/Co⁴⁺ caused by auto-oxidation process. Importantly, the in situ Raman spectrum exhibits the vibration signal of Co–OH in the non-Faradaic potential interval for oxygen evolution reaction, which is considered the initial step in reconstruction process. Density functional theory and ab initio molecular dynamics are used to elucidate this process at the atomic scale: First, OH⁻ exhibits a lower adsorption energy barrier and proton desorption energy barrier at the configuration surface, which proposes the formation of a single oxygen (–O) group. Under a higher –O group coverage, the Co–P bond is destroyed along with the PO_x groups. Subsequently, lower P vacancy formation energy confirm that the Ni-CoP configuration can fast transform into a highly active phase. Based on the optimized reconstruction behavior and rate-limiting barrier, the Ni-CoP nanowire exhibit an excellent overpotential of 1.59 V at 10 mA cm⁻² for overall water splitting, which demonstrates low degradation (2.62%) during the 100 mA cm⁻² for 100 h. This work provide systematic insights into the atomic-level reconstruction mechanism of transition metal phosphides, which benefit further design of water splitting catalysts.

The oxygen evolution reaction (OER) electrocatalysts, which can keep active for a long time in acidic media, are of great significance to proton exchange membrane water electrolyzers. Here, Ru-Co₃O₄ electrocatalysts with transition metal oxide Co₃O₄ as matrix and the noble metal Ru as doping element have been prepared through an ion exchange–pyrolysis process mediated by metal-organic framework, in which Ru atoms occupy the octahedral sites of Co₃O₄. Experimental and theoretical studies show that introduced Ru atoms have a passivation effect on lattice oxygen. The strong coupling between Ru and O causes a negative shift in the energy position of the O p-band centers. Therefore, the bonding activity of oxygen in the adsorbed state to the lattice oxygen is greatly passivated during the OER process, thus improving the stability of matrix material. In addition, benefiting from the modulating effect of the introduced Ru atoms on the metal active sites, the thermodynamic and kinetic barriers have been significantly reduced, which greatly enhances both the catalytic stability and reaction efficiency of Co₃O₄.

Under the complex external reaction conditions, uncovering the true structural evolution of the catalyst is of profound significance for the establishment of relevant structure–activity relationships and the rational design of electrocatalysts. Here, the surface reconstruction of the catalyst was characterized by ex-situ methods and in-situ Raman spectroscopy in CO₂ electroreduction. The final results showed that the Bi₂O₃ nanoparticles were transformed into Bi/Bi₂O₃ two-dimensional thin-layer nanosheets (NSs). It is considered to be the active phase in the electrocatalytic process. The Bi/Bi₂O₃ NSs showed good catalytic performance with a Faraday efficiency (FE) of 94.8% for formate and a current density of 26 mA cm⁻² at −1.01 V. While the catalyst maintained a 90% FE in a wide potential range (−0.91 V to −1.21 V) and long-term stability (24 h). Theoretical calculations support the theory that the excellent performance originates from the enhanced bonding state of surface Bi-Bi, which stabilized the adsorption of the key intermediate OCHO* and thus promoted the production of formate.

Despite the tremendous efforts devoted to enhancing the activity of oxygen evolution reaction (OER) catalysts, there is still a huge challenge to deeply understand the electronic structure characteristics of transition metal oxide to guide the design of more active catalysts. Herein, Fe₃O₄ with oxygen vacancies (Fe₃O₄-Vac) was synthesized via Ar ion irradiation method and its OER activity was greatly improved by properly modulating the electron density around Fe atoms. The electron density of Fe₃O₄-Vac around Fe atoms increased compared to that of Fe₃O₄ according to the characterization of synchrotron-based X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS) spectra, and density functional theory (DFT) calculation. Moreover, the DFT results indicate the enhancement of the desorption of HOO* groups which significantly reduced the OER reaction barrier. Fe₃O₄-Vac catalyst shows an overpotential of 353 mV, lower than that of FeOOH (853 mV) and Fe₃O₄ (415 mV) at 10 mA cm⁻², and a low Tafel slope of 50 mV dec⁻¹ in 1 M KOH, which was even better than commercial RuO₂ at high potential. This modulation approach provides us with valuable insights for exploring efficient and robust water-splitting electrocatalysts.