The mechanistic interplay between the oxygen evolution reaction (OER) and material degradation during water electrolysis is not yet well understood even for the most studied OER electrocatalysts such as RuO2 and IrO2. It is still disputed whether the lattice oxygen mechanism (LOM) may be competitive with the conventional adsorbate evolving mechanism (AEM) of the OER in these materials and, if so, under what conditions. Herein, we employ density functional theory calculations to demonstrate that the LOM can give rise to higher OER activity than the AEM at the active sites involving structural defects, both intrinsic and extrinsic. Specifically, we show that, although the AEM is preferred for the perfect (110) and (211) surfaces, the formation of metal vacancies due to catalyst dissolution may lead to much lower OER overpotentials for the LOM. Also, by screening several metal impurities in RuO2, we reveal that dopants such as Ni and Co can promote the LOM over the AEM even for the perfectly structured surfaces. Overall, we demonstrate that defective IrO2 is less LOM active than RuO2 that should contribute to its superior stability under OER conditions.

A strategy to modulate the electrocatalytic activity of copper towards CO 2 reduction involving adsorption of acrylamide, acrylic acid and allylamine polymers is presented. Modification of electrodeposited copper foam with poly(acrylamide) leads to a significant enhancement in faradaic efficiency for ethylene from 13% (unmodified foam) to 26% at-0.96 V vs. RHE, whereas methane yield is unaffected. Effects from crystalline phase distribution and copper oxide phases are ruled out as the source of enhancement through XPS and in-situ XRD analysis. DFT calculations reveal that poly(acrylamide) adsorbs on the copper surface via the oxygen atom on the carbonyl groups, and enhances ethylene formation by i) charge donation to the copper surface that activates 1

The structural and electronic properties of the neutral and positively charged oxygen vacancies (F and F + centres) in the bulk and on the (001) surfaces of SrTiO3 crystal are examined within the hybrid Hartree-Fock and density functional theory (HF-DFT) method based upon the linear combination of atomic orbital (LCAO) approach. A comparison of the formation energy for surface and bulk defects indicates a perceptible propensity for the segregation of neutral and charged vacancies to both SrO and TiO2 surface terminations with a preference in the latter case which is important for interpretation of space charge effects at ceramic interfaces. It is found that the vacancies reveal more shallow energy levels in the band gap on surfaces rather than in the bulk, in particular, on the TiO2 surface. The charged F + centre has significantly deeper energy levels both in bulk and on the surfaces, as compared with the neutral F centre.

RuO 2 is one of the most active electrocatalysts toward oxygen evolution reaction (OER), but it suffers from rapid dissolution in electrochemical environments. It is also established experimentally that corrosion of metal oxides can, in fact, promote catalytic activity for OER owing to the formation of a surface hydrous amorphous layer. However, the mechanistic interplay between corrosion and OER across metal-oxide catalysts and to what degree these two processes are correlated are still debated. Herein, we employ ab initio molecular dynamics-based blue moon ensemble approach in combination with OER thermodynamic analysis to reveal a clear mechanistic coupling between Ru dissolution and OER at the RuO 2 (110)/water interface. Specifically, we demonstrate that (i) dynamic transitions between metastable dissolution intermediates greatly affect catalytic activity toward OER, (ii) dissolution and OER processes share common intermediates with OER promoting Ru detachment from the surface, (iii) the lattice oxygen can be involved in the OER, and (iv) the coupling between different OER intermediates formed at the same Ru site of the metastable dissolution state can lower the theoretical overpotential of OER down to 0.2 eV. Collectively, our findings illustrate the critical role of highly reactive metastable dissolution intermediates in facilitating OER and underscore the need for the incorporation of interfacial reaction dynamics to resolve apparent conflicts between theoretically predicted and experimentally measured OER overpotentials.

The structure of IrO2 during the oxygen evolution reaction (OER) was studied by operando X-ray absorption spectroscopy (XAS) at the Ir L3-edge to gain insight into the processes that occur during the electrocatalytic reaction at the anode during water electrolysis. For this purpose, calcined and uncalcined IrO2 nanoparticles were tested in an operando spectroelectrochemical cell. In situ XAS under different applied potentials uncovered strong structural changes when changing the potential. Modulation excitation spectroscopy combined with XAS enhanced the information on the dynamic changes significantly. Principal component analysis (PCA) of the resulting spectra as well as FEFF9 calculations uncovered that both the Ir L3-edge energy and the white line intensity changed due to the formation of oxygen vacancies and lower oxidation state of iridium at higher potentials, respectively. The deconvoluted spectra and their components lead to two different OER modes. It was observed that at higher OER potentials, the well-known OER mechanisms need to be modified, which is also associated with the stabilization of the catalyst, as confirmed by in situ inductively coupled plasma mass spectrometry (ICP-MS). At these elevated OER potentials above 1.5 V, stronger Ir–Ir interactions were observed. They were more dominant in the calcined IrO2 samples than in the uncalcined ones. The stronger Ir–Ir interaction upon vacancy formation is also supported by theoretical studies. We propose that this may be a crucial factor in the increased dissolution stability of the IrO2 catalyst after calcination. The results presented here provide additional insights into the OER in acid media and demonstrate a powerful technique for quantifying the differences in mechanisms on different OER electrocatalysts. Furthermore, insights into the OER at a fundamental level are provided, which will contribute to further understanding of the reaction mechanisms in water electrolysis.