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Understanding what controls the reaction rate on iridium-based catalysts is central to designing more active and stable electrocatalysts for the water oxidation reaction in proton exchange membrane (PEM) electrolysers. Here, we quantify the densities of redox active centres and probe their binding strengths on amorphous IrOx and rutile IrO2 using a combination of operando time-resolved optical spectroscopy, X-ray absorption spectroscopy (XAS) and time of flight secondary ion mass spectrometry (TOF-SIMs). Firstly, our results show that although IrOx exhibits an order of magnitude higher geometry current density compared to IrO2, the intrinsic rates of reaction per active state, on IrOx and IrO2 are comparable at a given potential. Secondly, we establish a quantitative experimental correlation between the intrinsic rate of water oxidation and the energetics of the active states. We use density functional theory (DFT) based models to provide a molecular scale interpretation of our data. We find that the *O species formed at water oxidation potentials have repulsive adsorbate-adsorbate interactions, and thus increasing their coverage weakens their binding and promotes the rate-determining O-O bond formation. Finally, we provide insights into how the intrinsic water oxidation kinetics can be increased by optimising both the binding energy and the interaction strength of the catalytically active states.

The use of ionic liquid layers has been reported to improve both the activity and durability of several oxygen reduction catalysts. However, the development of this technology has been hindered by the lack of understanding of the mechanism behind this performance enhancement. In this work, we use a library of ionic liquids to modify a model FeN4 catalyst (iron phthalocyanine), to decouple the effects of ionic liquid layers on oxygen reduction kinetics and oxygen transport. Our results show that oxygen reduction activity at low overpotentials it determined by the ionic liquids’ influence on the *OH binding energy on the active sites, while oxygen solubility controls transport at high overpotentials. Finally, using porosimetry, we have demonstrated that the distribution of the ionic liquids on the catalyst is inhomogeneous, and depends on the nature of the ionic liquid used.

The electrochemical CO2 reduction reaction (CO2RR) to value-added chemicals with renewable electricity is a promising method to decarbonise parts of the chemical industry. Recently, single metal atoms in nitrogen-doped carbon (MNC) have emerged as potential electrocatalysts for CO2RR to CO with high activity and faradaic efficiency, although the reaction limitation for CO2RR to CO is unclear. To understand the comparison of intrinsic activity of different MNCs, we synthesized two catalysts through a decoupled two-step synthesis approach of high temperature pyrolysis and low temperature metalation (Fe or Ni). The highly meso-porous structure resulted in the highest reported electrochemical active site utilisation based on in situ nitrite stripping; up to 59±6% for NiNC. Ex-situ X-ray absorption spectroscopy confirmed the penta-coordinated nature of the active sites. The catalysts are amongst the most active in the literature for CO2 reduction to CO. Our density functional theory calculations (DFT) show that their binding to the reaction intermediates approximates to that of Au surfaces. However, we find that the TOFs of the most active catalysts for CO evolution converge, suggesting a fundamental ceiling to the catalytic rates.

The electrochemical conversion of biomass to high-value platform chemicals as a potential means to reduce our reliance on crude oil, offers environmental advantages in comparison to thermal catalysis as it...

The lithium-mediated system catalyses nitrogen to ammonia under ambient conditions. Herein we discover that trace amount of water - in contrast to prior reports from the literature – can effect a dramatic improvement in the Faradaic selectivity of N2 reduction to NH3. We report an optimal water concentration of 35.5 mM and LiClO4 salt concentration of 0.8 M allows a Faradaic efficiency up to 27.7% at ambient pressure. We attribute the increase in Faradaic efficiency to the incorporation of Li2O in the solid electrolyte interphase, as suggested by our X-ray photoelectron spectroscopy measurements. Our results highlight the extreme sensitivity of lithium mediated N2 reduction to small changes in the experimental conditions.

Electrochemical production of hydrogen peroxide, H2O2, holds promise for small-scale, on spot, and safe production of green oxidizer. Electrochemical process requires small electrochemical device that can replace large and centralized current infrastructure using anthraquinone method. Optimizing cathode catalyst that can reduce oxygen to hydrogen peroxide with high activity and high selectivity will make such a system reality. We focus on the catalysis of electrochemical oxygen reduction to hydrogen peroxide. Electronic effect and geometric effect are the two important factors determining activity and selectivity of catalysts. Beyond these well-known effects, pH and mass transport of product can profoundly change the activity and the selectivity of catalyst. Activity and selectivity of Pt-Hg, Ag-Hg, Ag, and glassy carbon electrode abruptly changed by pH of reaction environment. We also highlight the importance of mass transport on benchmarking the selectivity by comparing three different systems with different mass transport phenomena, rotating ring disk electrode, stagnant electrode, and membrane electrode assembly. We propose single-atom catalyst as a promising type of catalyst for H2O2 production. Single-atom catalysts exhibit intriguing catalytic properties due to its geometric arrangement where active atoms are well separated with each other, and each individual atom directly interact with support atoms. Single-atom catalyst can satisfy both electronic and geometric effect for the optimized performance. Near hundred percent noble metal utilization led to high mass activity for electrochemical H2O2 production.

Short chain alkanes and alkenes (C1-4) typically have little economic value and are difficult to transport since they are gases. Because of this, these hydrocarbons are of so low value that they are often flared during extraction of oil.1 This talk investigates electrochemically partially oxidizing these materials to high-value liquid products, thus increasing both the value and ease in transportation. If the oxidation is cathodic enough (< ~ +0.9 V vs. RHE) this can be combined with a standard oxygen reduction reaction cathode in a PEM fuel cell type approach to produce a device that does not consume electrical power, but actually has the potential to produce a small amount of power.2 Specifically this talk focuses on partial electrochemical oxidation of propylene to a variety of high value products such as acrolein, propylene oxide, propylene glycol, and acrylic acid and low value products such as CO2, and acetic acid. Using a Pd catalyst, we analyse the effects of pre-treatment, potential, pH and other factors in optimizing high value products while minimizing low value products. As shown below, one of the most promising findings is a high degree of acrolein selectivity at 0.9 V vs RHE in acidic solutions. The figure below shows that we can achieve stable electrochemical oxidation of propylene for 1 hour and produce acrolein with a selectivity of near 80%. Elvidge, C. D.; Ziskin, D.; Baugh, K. E.; Tuttle, B. T.; Ghosh, T.; Pack, D. W.; Erwin, E. H.; Zhizhin, M., A Fifteen Year Record of Global Natural Gas Flaring Derived from Satellite Data. Energies 2009, 2 (3), 595-622. Yamanaka, I., Active control of catalysis and product selectivity by a fuel cell system. Research on Chemical Intermediates 2006, 32 (3-4), 373-38 Figure 1

Understanding the factors controlling trends in activity for electrocatalytic oxygen reduction is of fundamental interest; as this reaction is paramount for future energy conversion schemes.1 Recently, numerous reports have suggested significant divergences between catalytic performances of noble metal surfaces for this reaction in acidic and basic electrolyte.2 Prior work3 by us have elucidated the Sabatier volcano for the oxygen reduction reaction in 0.1 M HClO4 using the Cu/Pt(111) near-surface alloy system. In the present work the surface binding of *OH reaction intermediates were weakened by ligand effects introduced by varying subsurface Cu coverage in Pt(111). Thus, we related the observed oxygen electroreduction activities to the shifts in OH adsorption potentials, derived from the base cyclic voltammograms, in both acidic3 and alkaline media. Remarkably, similar trend persists between *OH binding shifts and Cu/Pt(111) oxygen reduction activities relative to pure Pt(111); this being independent of the electrolyte going from acid to alkaline. Notably, Cu/Pt(111) near-surface alloy surfaces in 0.1 M NaOH or KOH, while exhibiting similar trend in relative activity independent of electrolyte, exhibits a substantial ~2- and 4, respectively. This suggests a fundamental effect of changing the cation present in the electrolyte. Moreover, by optimizing the Cu subsurface content a substantial activity enhancement is observed, which in 0.1 M KOH results in exceptionally high specific activities on the order of 101±8 mA/cm2 at 0.9 V vs. the reversible hydrogen electrode. Hence, our results confirm that *OH binding energies governs the activity in both acid and alkaline media i.e. a Sabatier volcano relationship persist in alkaline media. Furthermore, our results open up discussions of relevant aspects describing the cation interplay with the catalyst surface. A. Kongkanand and M. F. Mathias, J. Phys. Chem. Lett., 7, 1127–1137 (2016). J. Staszak-Jirkovský et al., ACS Catal., 5, 6600–6607 (2015). I. E. L. Stephens et al., J. Am. Chem. Soc., 133, 5485–5491 (2011).