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Journal articleMoss B, Liang C, Carpenter A, et al., 2026, , Nature Reviews Methods Primers, Vol: 6
Correction to: Nature Reviews Methods Primershttps://doi.org/10.1038/s43586-025-00445-4, published online 20 November 2025. In the version of the article initially published, Reshma R. Rao and Ifan E. L. Stephens were incorrectly listed with affiliation 1 when it should have been affiliation 2 (Department of Materials, 911½ñÈÕºÚÁÏ, London, UK). In the “Collimation, colour balancing and light guides” section, the equation N=fD should have read N≈Df. In Fig. 1a, the label “σα(λ)” should have read “∆α(λ)”. In Fig. 5c, the colours in the key were switched and should have been a green dot for “PD — IRM” and the blue line should have been “J<inf>cat</inf>”. In Fig. 6a, the bottom label “Redox transition 3” should have been “Redox transition 1”. These corrections have been corrected in the HTML and PDF versions of the article.
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Journal articleYu Y, Wang Y, Ye H, et al., 2026, , J Am Chem Soc
Glycerol oxidation reaction (GOR) is a promising valorization route to upgrade the biodiesel by-product while coproducing green hydrogen at the cathode in electrolyzers. However, the working mechanism of transition-metal-based catalysts such as Ni(OH)2 remains poorly understood. Here, we employed a multioperando spectroelectrochemical approach combining UV-vis optical spectroscopy, X-ray absorption spectroscopy, and time-resolved stepped-potential spectroscopy to investigate the active oxidizing species and charge-transfer dynamics under OER and GOR conditions. We identified NiOOH (Ni3+) as the active species for GOR, whereas the formation of higher-valent NiOO (Ni4+) species is completely suppressed in the presence of glycerol. The accumulation of surface-adsorbed glycerol molecules is the rate-determining step (τ ∼ 27.9 s at 1.47 VRHE), occurring slower than the intrinsic catalytic step of glycerol reaction (τ ∼ 3.2 s at 1.47 VRHE), which involves oxidation and bond cleavage. In contrast, the kinetics of the OER are significantly slower (τ ∼ 167 s at 1.47 VRHE), resulting in the dominance of GOR and suppression of oxygen evolution in the presence of glycerol. The potential-independent production of formic acid during GOR follows an apparent first-order dependence on NiOOH concentration, suggesting continuous C-C bond cleavage activated by reactive *O species. These findings link oxidizing species with charge-transfer dynamics, providing insight for the rational design of Ni-based catalysts for glycerol and other biomass-derived molecule oxidations.
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Journal articleWang Y, Twight LP, Sagui NA, et al., 2026, , ACS Catal, Vol: 16, Pages: 6749-6757, ISSN: 2155-5435
Ni x Fe1-x O y H z is the state-of-the-art catalyst for the oxygen evolution reaction (OER) in alkaline water electrolyzers; however, understanding the impact of Fe on the active sites, reaction mechanism, and consequently intrinsic activity has been under intense debate. In this work, operando UV-vis spectroscopy was used to investigate Fe-free NiO x H y and NiO x H y with Fe selectively incorporated onto the surface. At oxygen-evolution potentials, similar oxidized nickel states were present before and after the Fe incorporation, with negligible changes in their redox potentials. However, the discharge kinetics of the Ni states show a substantial acceleration after the introduction of Fe, consistent with an increase in OER kinetics upon Fe incorporation and formation of active Ni-Fe species. Using optical spectroscopy, we determined the intrinsic reaction time constant per surface Fe site is <0.1 s, which is 2 orders of magnitude faster than Ni sites not in proximity to surface Fe sites (∼10 s), and also an order of magnitude faster than Ni sites in pure NiO x H y (∼1 s). Consequently, we propose that the OER occurs via charge accumulation primarily on Ni centers in these catalysts, followed by hole transport to the surface Fe species where oxygen evolution occurs.
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Journal articleTao Y, Utsunomiya T, Yu H, et al., 2026, , ACS Appl Mater Interfaces, Vol: 18, Pages: 15699-15710
Understanding the electrode/electrolyte interface is essential for tuning electrocatalyst activity. Here, we combine operando optical spectroscopy, laser-induced current transient (LICT) measurements, and surface-enhanced infrared absorption spectroscopy (SEIRAS) to investigate the origin of cation-dependent oxygen evolution reaction (OER) activity on electrodeposited iridium oxide in 0.1 M MOH (M = TMA+, K+, Na+, and Li+). We find that OER activity increases with increasing cation size (TMAOH > KOH > NaOH > LiOH). Operando optical spectroscopy reveals that the energetics of the redox transitions and the population of the redox-active species are independent of the electrolyte. Instead, the intrinsic turnover frequency varies strongly with the nature of the cation. LICT, SEIRAS, and quantum mechanics/molecular mechanics (QM/MM) simulations suggest that the interfacial solvent structure is the origin of this difference. With increasing cation size, the fraction of isolated water molecules and cation-coordinated water molecules increases, producing a more disordered interfacial environment. LICT measurements confirm that the potential of maximum entropy shifts closer to the water oxidation potential in the presence of larger cations in the electrolyte. We propose that a more disordered interface results in more isolated and reactive OH- ions and faster reorganization of the interfacial solvent structure during the rate-determining O-O bond formation step, thereby accelerating the OER kinetics. Through our work, using multimodal operando spectroscopy and molecular simulations, we highlight how interfacial solvent structure, controlled by electrolyte cations, governs reactivity at complex electrochemical interfaces.
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Journal articleGaje A, Rao R, Mesa CA, et al., 2026, , Nature Catalysis, Vol: 9, Pages: 248-256
Current research into (photo)electrocatalysis is focused on increasing the reactivity of systems based on Earth-abundant elements, which requires kinetic models of their catalytic mechanisms. In transition metal oxides, adsorption and electron transfer steps typically involve changes in the oxidation state of the metal and the colour of the electrode, which can be measured spectroscopically. In situ spectroelectrochemical studies have exposed the unexpected role played by the density of active species and their co-operativity in dictating (photo)electrochemical performance. Here we review how reaction pathways can be controlled by the presence, or not, of molecular-scale interactions between redox active sites at the interface and discuss strategies to monitor them. We consider how the ability to probe and quantify such interactions opens strategies to enhance catalytic performance and creates opportunities for scientific discovery. (Figure presented.)
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Journal articleLiang C, Garcia Verga L, Moss B, et al., 2026, , Nat Mater
Oxidation states underpin the understanding of active states, reaction mechanisms and catalytic performance of electrocatalysts. However, determining them at complex solid-liquid interfaces is challenging. Here we use multimodal spectroscopy to investigate polarized iridium oxide (IrOx) electrodes, a model water oxidation catalyst, to identify potential-dependent iridium and oxygen oxidation states. By integrating multiple operando spectroscopies (optical (ultraviolet-visible), Ir L-edge and O K-edge X-ray absorption spectroscopy) with electrochemistry mass spectrometry and density functional theory calculations, we identify the sequential depletion of electron densities from the Ir5d band (corresponding to Ir3+→Ir4+→Ir5+), followed by electron removal from the O2p band, forming electrophilic oxygen species (O-1) due to enhanced Ir-O covalency and electronic state overlap. Time-resolved measurements reveal distinct lifetimes for Ir5+ and O-1 states under water oxidation conditions, Ir5+ remains unreactive whereas O-1 is consumed at a time constant commensurate with the reaction rate, indicating that O-1 drives the oxygen evolution reaction. These findings demonstrate the necessity of using multiple operando techniques to gain a unified understanding of the evolution of oxidation states and active sites with potential for water oxidation on oxide catalysts.
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Journal articleDuarte RPM, Rao R, Ryan MP, et al., 2026, , EES Catalysis, Vol: 4, Pages: 55-76, ISSN: 2753-801X
Zinc–air redox flow batteries have high potential to penetrate the stationary energy storage market, due to the abundancy, and low cost of active species – oxygen and zinc. However, their technological fruition is limited by the development of reversible O2 electrodes operating at potentials between 0.6 VRHE to 1.7 VRHE, under which no catalyst material has been shown to be stable over long durations. Despite heavy research on the topic of reversible O2 catalysis, little is known about the parameters controlling the stability of the bifunctional catalyst. Several research accounts assess the activity of reversible O2 catalysts, but only a small portion cover degradation mechanism over such a large potential window. In this perspective, we summarize our current understanding of material challenges for Zn–air batteries, reversible O2 catalyst integration strategies, and electrochemical behaviour, with a particular focus on catalyst stability. Nickel cobalt oxide (NiCo2O4), a promising yet understudied system, is used as an example material for investigations at potentials of both the O2 reduction (ORR) and evolution (OER) reactions. We also report original data employing ex situ X-ray diffraction, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy, as well as electrochemical measurements to study the activity of NiCo2O4. Furthermore, electrochemical accelerated stress tests are coupled with post-mortem transmission electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy to study the dissolution, compositional changes and amorphization of the top surface 5 nm of the catalyst surface. In situ X-ray absorption spectroscopy revealed irreversible oxidation of Co centres in NiCo2O4 during OER, which explains the reduction in activity of the ORR after the catalyst was exposed to anodic OER potentials. This methodology provides a broader method to screen reversible O2 catalyst stability and enables us to sum
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Journal articleMoss B, Liang C, Carpenter A, et al., 2025, , NATURE REVIEWS METHODS PRIMERS, Vol: 5
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Journal articleSibug-Torres SM, Niihori M, Wyatt E, et al., 2025, , NATURE CHEMISTRY, ISSN: 1755-4330
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Journal articleQuintin-Baxendale R, Sokolikova M, Tao Y, et al., 2025, , ACS Materials Au, ISSN: 2694-2461
IrO2 is one of the most widely investigated electrocatalysts for oxygen evolution reaction in an acidic environment. Increasing the mass activity is an effective way of decreasing the loading of Ir, to ultimately reduce costs. Here, we demonstrate the crystal-phase engineering of two different potassium iridate polymorphs obtained by designing a selective solid-state synthesis of either one-dimensional K0.25IrO2 nanowires with a hollandite crystal structure or two-dimensional KIrO2 hexagonal platelets. Both structures present increased specific and mass electrocatalytic activities for the water oxidation reaction in acidic media compared to commercial rutile IrO2 of up to 40%, with the 1D nanowires outperforming the 2D platelets. XANES, extended X-ray absorption fine structure, and X-ray diffraction investigations prove the structural stability of these two different allotropes of KxIrO2 compounds upon electrocatalytic testing. These low-dimensional nanostructured 1D and 2D KxIrO2 compounds with superior mass activity to commercial IrO2 can pave the way toward the design of new electrocatalyst architectures with reduced Ir loading content for proton exchange membrane water electrolyzer (PEMWE) anodes.
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