Synthetic approaches to artificial photosynthesis: general discussion

Metals in Catalysis, Biomimetics & Inorganic Material

Strategies to improve light utilization in solar fuel synthesis

The synthesis of fuels using sunlight offers a promising sustainable solution for chemical energy storage, but inefficient utilization of the solar spectrum limits its commercial viability. Apart from fundamental improvements to (photo)catalyst materials, solar fuel production systems can also be designed to improve solar energy utilization by integrating complementary technologies that more efficiently utilize the solar spectrum. Here we review recent progress on emerging complementary approaches to better modify, enhance or distribute solar energy for sunlight-to-fuel conversion, including advanced light management, integrated thermal approaches and solar concentrators. These strategies can improve the efficiency and production rates of existing photo(electro)chemical systems and, therefore, the overall economics of solar fuel production. More broadly, the approaches highlight the necessary collaboration between materials science and engineering to help drive the adoption of a sustainable energy economy using existing technologies

Bacteria–photocatalyst sheet for sustainable carbon dioxide utilization

The clean conversion of carbon dioxide and water to a single multicarbon product and O2 using sunlight via photocatalysis without the assistance of organic additives or electricity remains an unresolved challenge. Here we report a bio-abiotic hybrid system with the nonphotosynthetic, CO2-fixing acetogenic bacterium, Sporomusa ovata (S. ovata) grown on a scalable and cost-effective photocatalyst sheet consisting of a pair of particulate semiconductors (La and Rh co-doped SrTiO3 (SrTiO3:La,Rh) and Mo-doped BiVO4 (BiVO4:Mo)). The biohybrid effectively produces acetate (CH3COO–) and oxygen (O2) using only sunlight, CO2 and H2O, achieving a solar-to-acetate conversion efficiency of 0.7%. The photocatalyst sheet oxidises water to O2 and provides electrons and hydrogen (H2) to S. ovata for the selective synthesis of CH3COO– from CO2. To demonstrate the utility in a closed carbon cycle, the solar-generated acetate was used directly as feedstock in a bioelectrochemical system for electricity generation. These semi-biological systems thus offer a promising strategy for sustainably and cleanly fixing CO2 and closing the carbon cycle

Reforming of Soluble Biomass and Plastic Derived Waste Using a Bias-Free Cu<inf>30</inf>Pd<inf>70</inf>

Abstract: The production of clean fuels and chemicals from waste feedstocks is an appealing approach towards creating a circular economy. However, waste photoreforming commonly employs particulate photocatalysts, which display low product yields, selectivity, and reusability. Here, a perovskite‐based photoelectrochemical (PEC) device is reported, which produces H2 fuel and simultaneously reforms waste substrates. A novel Cu30Pd70 oxidation catalyst is integrated in the PEC device to generate value‐added products using simulated solar light, achieving 60–90% product selectivity and ≈70–130 µmol cm−2 h−1 product formation rates, which corresponds to 102–104 times higher activity than conventional photoreforming systems. The single‐light absorber device offers versatility in terms of substrate scope, sustaining unassisted photocurrents of 4–9 mA cm−2 for plastic, biomass, and glycerol conversion, in either a two‐compartment or integrated “artificial leaf” configuration. These configurations enable an effective reforming of non‐transparent waste streams and facile device retrieval from the reaction mixture. Accordingly, the presented PEC platform provides a proof‐of‐concept alternative towards photoreforming, approaching more closely the performance and versatility required for commercially viable waste utilization

Bifunctional Perovskite‐BiVO 4 Tandem Devices for Uninterrupted Solar and Electrocatalytic Water Splitting Cycles

Photoelectrochemical (PEC) fuel synthesis depends on the intermittent solar intensity of the diurnal cycle and ceases at night. Here, an integrated device that does not only possess PEC water splitting functionality, but also operates as an electrolyzer in the nocturnal period to improve the overall capacity factor is described. The bifunctional system is based on an “artificial leaf” tandem PEC architecture that contains an inverse‐structure lead halide perovskite protected by a graphite epoxy/parylene‐C coating (conferring 96 h stability of operation in water), and a porous BiVO4 semiconductor. The light‐absorbers are interfaced with a H2 evolution catalyst (Pt) and a Co‐based water oxidation catalyst, respectively, which can also be directly driven by electricity. Thus, the device can operate in PEC mode during irradiation and switch to an electricity‐powered mode in the dark through bypassing of the semiconductor configuration. The bifunctional perovskite‐BiVO4 tandem provides a solar‐to‐hydrogen efficiency of 1.3% under simulated solar irradiation and an onset for water electrolysis at 1.8 V. The compact design and low cost of the proposed device may provide an advantage over other technologies for round‐the‐clock fuel production