There is intense interest in the solar driven conversion of water to hydrogen as a means of achieving the sustainable generation of a practical fuel. It is widely considered that such "Artificial Photosynthesis" processes need to achieve an energy conversion efficiency exceeding 10 % to have practical impact. Although some solar--driven fuel generating systems have reached efficiencies as high as 18 %, they are often based on precious metal catalysts, or offer only limited stability.We describe here a system that utilises concentrated solar power, which is inexpensive to produce, and an electrolyser module based on Earth--abundant materials capable of operating under benign conditions. This system delivers the highest efficiency reported to date, in excess of 22 %. The electrolyser functions in electrolytes with pH values ranging from neutral to alkaline, including river water, allowing implementation in a variety of geographic locations. Testing over multiple diurnal cycles confirmed the long--term stability of performance. We also describe an analysis of the efficiency in terms of the critical cell--matching parameters and thereby understand the key directions for further optmisation. This simple and adaptable system addresses key criteria for the large--scale deployment of an artificial photosynthesis device.

Soft X-ray absorption and resonant inelastic X-ray scattering at the Mn Ledge are established as tools for gaining electronic structural insights into water oxidation catalysis. The MnO x catalyst with the lowest d-d transitions, strongest charge transfer and a higher proportion of Mn 3+ over Mn 2+/4+ produces itinerant electrons that contribute to a higher catalytic activity.

A novel architecture for quasi-interdigitated electrodes (QIDEs) allows for the fabrication of back-contacted perovskite solar cells.

Detection and quantification of redox transformations involved in water oxidation electrocatalysis is often not possible using conventional techniques. Herein, use of large amplitude Fourier transformed ac voltammetry and comprehensive analysis of the higher harmonics has enabled us to access the redox processes responsible for catalysis. An examination of the voltammetric data for water oxidation in borate buffered solutions (pH 9.2) at electrodes functionalized with systematically varied low loadings of cobalt (CoO), manganese (MnO), and nickel oxides (NiO) has been undertaken, and extensive experiment-simulation comparisons have been introduced for the first time. Analysis shows that a single redox process controls the rate of catalysis for Co and Mn oxides, while two electron transfer events contribute in the Ni case. We apply a "molecular catalysis" model that couples a redox transformation of a surface-confined species (effective reversible potential, E) to a catalytic reaction with a substrate in solution (pseudo-first-order rate constant, k), accounts for the important role of a Brønsted base, and mimics the experimental behavior. The analysis revealed that E values for CoO, MnO, and NiO lie within the range 1.9-2.1 V vs reversible hydrogen electrode, and k varies from 2 × 10 to 4 × 10 s. The k values are much higher than reported for any water electrooxidation catalyst before. The E values provide a guide for in situ spectroscopic characterization of the active states involved in catalysis by metal oxides.

Light-driven conversion of CO 2 to chemicals provides a sustainable alternative to fossil fuels, but homogeneous systems are typically limited by cross reactivity between different redox half reactions and inefficient charge separation. Herein, we present the bioinspired development of amphiphilic photosensitizer and catalyst pairs that self-assemble in lipid membranes to overcome some of these limitations and enable photocatalytic CO 2 reduction in liposomes using precious metal-free catalysts. Using sodium ascorbate as a sacrificial electron source, a membrane-anchored alkylated cobalt porphyrin demonstrates higher catalytic CO production (1456 vs 312 turnovers) and selectivity (77 vs 11%) compared to its water-soluble nonalkylated counterpart. Time-resolved and steady-state spectroscopy revealed that self-assembly facilitates this performance enhancement by enabling a charge-separation state lifetime increase of up to two orders of magnitude in the dye while allowing for a ninefold faster electron transfer to the catalyst. Spectroelectrochemistry and density functional theory calculations of the alkylated Co porphyrin catalyst support a four-electron-charging mechanism that activates the catalyst prior to catalysis, together with key catalytic intermediates. Our molecular liposome system therefore benefits from membrane immobilization and provides a versatile and efficient platform for photocatalysis.

Manganese oxide (MnO x )electrocatalysts are examined herein by in situ soft X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) during the oxidation of water buffered by borate (pH 9.2) at potentials from 0.75 to 2.25 Vv s. the reversible hydrogen electrode. Correlation of L-edge XAS data with previous mechanistic studies indicates Mn IV is the highest oxidation state involved in the catalytic mechanism. MnO x is transformed into birnessite at 1.45 Vand does not undergo further structural phase changes. At potentials beyond this transformation, RIXS spectra show progressive enhancement of charge transfer transitions from oxygen to manganese.T heoretical analysis of these data indicates increased hybridization of the Mn À Oo rbitals and withdrawal of electron density from the Oligand shell. In situ XAS experiments at the OK -edge providec omplementary evidence for such at ransition. This step is crucial for the formation of O 2 from water.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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The instability and expense of anodes for water electrolyzers with acidic electrolytes can be overcome through the implementation of a cobalt‐iron‐lead oxide electrocatalyst, [Co–Fe–Pb]Ox, that is self‐healing in the presence of dissolved metal precursors. However, the latter requirement is pernicious for the membrane and especially the cathode half‐reaction since Pb2+ and Fe3+ precursors poison the state‐of‐the‐art platinum H2 evolving catalyst. To address this, we demonstrate the invariably stable operation of [Co–Fe–Pb]Ox in acidic solutions through a cobalt‐selective self‐healing mechanism without the addition of Pb2+ and Fe3+ and investigate the kinetics of the process. Soft X‐ray absorption spectroscopy reveals that low concentrations of Co2+ in the solution stabilize the catalytically active Co(Fe) sites. The highly promising performance of this system is showcased by steady water electrooxidation at 80±1 °C and 10 mA cm−2, using a flat electrode, at an overpotential of 0.56±0.01 V on a one‐week timescale.