Semiartificial Photosynthetic Nanoreactors for H Generation.

A relatively unexplored energy source in synthetic cells is transmembrane electron transport, which like proton and ion transport can be light driven. Here, synthetic cells, called nanoreactors, are engineered for compartmentalized, semiartificial photosynthetic H production by a [FeFe]-hydrogenase (Hase). Transmembrane electron transfer into the nanoreactor was enabled by MtrCAB, a multiheme transmembrane protein from MR-1.

Solar Fuel Synthesis Using a Semiartificial Colloidal Z-Scheme.

The integration of enzymes with semiconductor light absorbers in semiartificial photosynthetic assemblies offers an emerging strategy for solar fuel production. However, such colloidal biohybrid systems rely currently on sacrificial reagents, and semiconductor-enzyme powder systems that couple fuel production to water oxidation are therefore needed to mimic an overall photosynthetic reaction. Here, we present a Z-scheme colloidal enzyme system that produces fuel with electrons sourced from water.

Solar-Driven Methanogenesis through Microbial Ecosystem Engineering on Carbon Nitride.

Semi-biological photosynthesis combines synthetic photosensitizers with microbial catalysts to produce sustainable fuels and chemicals from CO. However, the inefficient transfer of photoexcited electrons to microbes leads to limited CO utilization, restricting the catalytic performance of such biohybrid assemblies. Here, we introduce a biological engineering solution to address the inherently sluggish electron uptake mechanism of a methanogen, Methanosarcina barkeri (M.

Engineering of bespoke photosensitiser-microbe interfaces for enhanced semi-artificial photosynthesis.

Biohybrid systems for solar fuel production integrate artificial light-harvesting materials with biological catalysts such as microbes. In this perspective, we discuss the rational design of the abiotic-biotic interface in biohybrid systems by reviewing microbes and synthetic light-harvesting materials, as well as presenting various approaches to coupling these two components together. To maximise performance and scalability of such semi-artificial systems, we emphasise that the interfacial design requires consideration of two important aspects: attachment and electron transfer.

Organic Semiconductor-BiVO Tandem Devices for Solar-Driven HO and CO Splitting.

Photoelectrochemical (PEC) devices offer a promising platform toward direct solar light harvesting and chemical storage through artificial photosynthesis. However, most prototypes employ wide bandgap semiconductors, moisture-sensitive inorganic light absorbers, or corrosive electrolytes. Here, the design and assembly of PEC devices based on an organic donor-acceptor bulk heterojunction (BHJ) using a carbon-based encapsulant are introduced, which demonstrate long-term H evolution and CO reduction in benign aqueous media.

Multi-Variable Multi-Metric Optimization of Self-Assembled Photocatalytic CO Reduction Performance Using Machine Learning Algorithms.

The sunlight-driven reduction of CO into fuels and platform chemicals is a promising approach to enable a circular economy. However, established optimization approaches are poorly suited to multivariable multimetric photocatalytic systems because they aim to optimize one performance metric while sacrificing the others and thereby limit overall system performance. Herein, we address this multimetric challenge by defining a metric for holistic system performance that takes multiple figures of merit into account, and employ a machine learning algorithm to efficiently guide our experiments through the large parameter matrix to make holistic optimization accessible for human experimentalists.

Electrostatic [FeFe]-hydrogenase-carbon nitride assemblies for efficient solar hydrogen production.

The assembly of semiconductors as light absorbers and enzymes as redox catalysts offers a promising approach for sustainable chemical synthesis driven by light. However, achieving the rational design of such semi-artificial systems requires a comprehensive understanding of the abiotic-biotic interface, which poses significant challenges. In this study, we demonstrate an electrostatic interaction strategy to interface negatively charged cyanamide modified graphitic carbon nitride (CN) with an [FeFe]-hydrogenase possessing a positive surface charge around the distal FeS cluster responsible for electron uptake into the enzyme.

High carrier mobility along the [111] orientation in CuO photoelectrodes.

Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight. Following a decade of advancement, CuO photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance.

Photocatalytic CO Reduction Using Homogeneous Carbon Dots with a Molecular Cobalt Catalyst.

A simple and precious-metal free photosystem for the reduction of aqueous CO to syngas (CO and H) is reported consisting of carbon dots (CDs) as the sole light harvester together with a molecular cobalt bis(terpyridine) CO reduction co-catalyst. This homogeneous photocatalytic system operates in the presence of a sacrificial electron donor (triethanolamine) in DMSO/HO solution at ambient temperature. The photocatalytic system exhibits an activity of 7.

Operando film-electrochemical EPR spectroscopy tracks radical intermediates in surface-immobilized catalysts.

The development of surface-immobilized molecular redox catalysts is an emerging research field with promising applications in sustainable chemistry. In electrocatalysis, paramagnetic species are often key intermediates in the mechanistic cycle but are inherently difficult to detect and follow by conventional in situ techniques. We report a new method, operando film-electrochemical electron paramagnetic resonance spectroscopy (FE-EPR), which enables mechanistic studies of surface-immobilized electrocatalysts.

Communities catalyzing change with data to mitigate an invisible menace, traffic-related air pollution.

Objectives: To identify strategies and tactics communities use to translate research into environmental health action.

Methods: We employed a qualitative case study design to explore public health action conducted by residents, organizers, and public health planners in two Massachusetts communities as part of a community based participatory (CBPR) research study. Data sources included key informant interviews (n = 24), reports and direct observation of research and community meetings (n = 10) and project meeting minutes from 2016-2021.

Solar reforming as an emerging technology for circular chemical industries.

The adverse environmental impacts of greenhouse gas emissions and persistent waste accumulation are driving the demand for sustainable approaches to clean-energy production and waste recycling. By coupling the thermodynamically favourable oxidation of waste-derived organic carbon streams with fuel-forming reduction reactions suitable for producing clean hydrogen or converting CO to fuels, solar reforming simultaneously valorizes waste and generates useful chemical products. With appropriate light harvesting, catalyst design, device configurations and waste pre-treatment strategies, a range of sustainable fuels and value-added chemicals can already be selectively produced from diverse waste feedstocks, including biomass and plastics, demonstrating the potential of solar-powered upcycling plants.

Valorisation of lignocellulose and low concentration CO using a fractionation-photocatalysis-electrolysis process.

The simultaneous upcycling of all components in lignocellulosic biomass and the greenhouse gas CO presents an attractive opportunity to synthesise sustainable and valuable chemicals. However, this approach is challenging to realise due to the difficulty of implementing a solution process to convert a robust and complex solid (lignocellulose) together with a barely soluble and stable gas (CO). Herein, we present the complete oxidative valorisation of lignocellulose coupled to the reduction of low concentration CO through a three-stage fractionation-photocatalysis-electrolysis process.

Connecting Biological and Synthetic Approaches for Electrocatalytic CO Reduction.

Electrocatalytic CO reduction has developed into a broad field, spanning fundamental studies of enzymatic 'model' catalysts to synthetic molecular catalysts and heterogeneous gas diffusion electrodes producing commercially relevant quantities of product. This diversification has resulted in apparent differences and a disconnect between seemingly related approaches when using different types of catalysts. Enzymes possess discrete and well understood active sites that can perform reactions with high selectivity and activities at their thermodynamic limit.

Size-dependent activity of carbon dots for photocatalytic H generation in combination with a molecular Ni cocatalyst.

Carbon dots (CDs) are low-cost light-absorbers in photocatalytic multicomponent systems, but their wide size distribution has hampered rational design and the identification of the factors that lead to their best performance. To address this challenge, we report herein the use of gel filtration size exclusion chromatography to separate amorphous, graphitic, and graphitic N-doped CDs depending on their lateral size to study the effect of their size on photocatalytic H evolution with a DuBois-type Ni cocatalyst. Transmission electron microscopy and dynamic light scattering confirm the size-dependent separation of the CDs, whereas UV-vis and fluorescence spectroscopy of the more monodisperse fractions show a distinct response which computational modelling attributes to a complex interplay between CD size and optical properties.

Chemoenzymatic Photoreforming: A Sustainable Approach for Solar Fuel Generation from Plastic Feedstocks.

Plastic upcycling through catalytic transformations is an attractive concept to valorize waste, but the clean and energy-efficient production of high-value products from plastics remains challenging. Here, we introduce chemoenzymatic photoreforming as a process coupling enzymatic pretreatment and solar-driven reforming of polyester plastics under mild temperatures and pH to produce clean H and value-added chemicals. Chemoenzymatic photoreforming demonstrates versatility in upcycling polyester films and nanoplastics to produce H at high yields reaching ∼10-10 μmol g and activities at >500 μmol g h.

Low-Volume Reaction Monitoring of Carbon Dot Light Absorbers in Optofluidic Microreactors.

Optical monitoring and screening of photocatalytic batch reactions using cuvettes is time-consuming, requires substantial amounts of samples, and does not allow the analysis of species with low extinction coefficients. Hollow-core photonic crystal fibers (HC-PCFs) provide an innovative approach for reaction detection using ultraviolet-visible absorption spectroscopy, with the potential for high-throughput automation using extremely low sample volumes with high sensitivity for monitoring of the analyte. HC-PCFs use interference effects to guide light at the center of a microfluidic channel and use this to enhance detection sensitivity.

Thermoelectric-Photoelectrochemical Water Splitting under Concentrated Solar Irradiation.

Photoelectrochemical devices could play a crucial role toward fuel production in a circular economy. Yet, light absorption suffers losses from thermalization and the inability to use low-energy photons. Here, we demonstrate that photoelectrochemical reactors can utilize this waste heat by integrating thermoelectric modules, which provide additional voltage under concentrated light irradiation.

Floating Carbon Nitride Composites for Practical Solar Reforming of Pre-Treated Wastes to Hydrogen Gas.

Solar reforming (SR) is a promising green-energy technology that can use sunlight to mitigate biomass and plastic waste while producing hydrogen gas at ambient pressure and temperature. However, practical challenges, including photocatalyst lifetime, recyclability, and low production rates in turbid waste suspensions, limit SR's industrial potential. By immobilizing SR catalyst materials (carbon nitride/platinum; CN |Pt and carbon nitride/nickel phosphide; CN |Ni P) on hollow glass microspheres (HGM), which act as floating supports enabling practical composite recycling, such limitations can be overcome.

Carboxysome-Inspired Electrocatalysis using Enzymes for the Reduction of CO at Low Concentrations.

The electrolysis of dilute CO streams suffers from low concentrations of dissolved substrate and its rapid depletion at the electrolyte-electrocatalyst interface. These limitations require first energy-intensive CO capture and concentration, before electrolyzers can achieve acceptable performances. For direct electrocatalytic CO reduction from low-concentration sources, we introduce a strategy that mimics the carboxysome in cyanobacteria by utilizing microcompartments with nanoconfined enzymes in a porous electrode.

Photosynthesis re-wired on the pico-second timescale.

Photosystems II and I (PSII, PSI) are the reaction centre-containing complexes driving the light reactions of photosynthesis; PSII performs light-driven water oxidation and PSI further photo-energizes harvested electrons. The impressive efficiencies of the photosystems have motivated extensive biological, artificial and biohybrid approaches to 're-wire' photosynthesis for higher biomass-conversion efficiencies and new reaction pathways, such as H evolution or CO fixation. Previous approaches focused on charge extraction at terminal electron acceptors of the photosystems.

Comproportionation of CO and Cellulose to Formate Using a Floating Semiconductor-Enzyme Photoreforming Catalyst.

Formate production via both CO reduction and cellulose oxidation in a solar-driven process is achieved by a semi-artificial biohybrid photocatalyst consisting of immobilized formate dehydrogenase on titanium dioxide (TiO |FDH) producing up to 1.16±0.04 mmol  g in 24 hours at 30 °C and 101 kPa under anaerobic conditions.

Hybrid photocathode based on a Ni molecular catalyst and SbSe for solar H production.

We report a H evolving hybrid photocathode based on SbSe and a precious metal free molecular catalyst. Through the use of a high surface area TiO scaffold, we successfully increased the Ni molecular catalyst loading from 7.08 ± 0.