The Use of Hybrid Photosynthesis-powering Biocatalysts

Inorganic chemistry is the chemistry of inorganic and organometallic compounds with their derivatives. Being that inorganic chemistry is the chemistry of everything else including every element in the periodic table as well as the use of carbon atoms, inorganic chemistry has a variety of applications in different subfields. Organometallic chemistry bridges both areas of organic and inorganic chemistry by the use of compounds containing direct metal-carbon bonds with the catalysis of many organic reactions. Bioinorganic chemistry combines both biochemistry and inorganic chemistry by the use of metalloproteins as well as artificially introduced metals, including those that are non-essential, in medicine and toxicology. Coordination chemistry involves the use of coordination compounds that pose as one or multiple metal centers that are bound by ligands. Solid-state chemistry, or materials chemistry, is the study of the synthesis, structure, and properties of novel solid-phase materials. Given that inorganic chemistry is made up of coordinate bonds due to a variety of properties and characteristics of metal complexes including coordination numbers, geometries, oxidation states, molecular orbital and group theories.

Fossil fuels are finite resources with indiscriminate utilizations that can cause significant harmful effects on the environment. A major negative environmental impact of fossil fuels is the release of large amounts of CO2 in the atmosphere. There have been research efforts aiming at powering CO2 reduction by means of solar energy at an industrial scale. Many of the bioproduction processes employing living organisms as catalysts for the synthesis of fuels rely on natural photosynthesis to acquire energy. Directly, this is done by means of photosynthetic plants, algae, or bacteria by converting inorganic carbon molecules into products. However, the percentages of solar-to-product conversion efficiency is very low and may cause a negative impact on agricultural yields. In comparison with natural photosynthesis, artificial photosynthesis systems where photoelectrochemical cells or solid-state photovoltaic apparatuses capture solar energy to drive fuel production are more efficient due to the high efficiency of light-absorbing materials being used. For example, photovoltaic cells have a solar energy-to-electricity conversion efficiency between 16% - 21% and can even be greater than 40% with the use of Si panels in multijunction cells, as compared to the natural production of ethanol from plants or oil from microalgae with a solar energy-to-electricity conversion efficiency of 0.2% - 1.5%. In recent applications, hybrid photosynthesis synthesis have claimed advantages of both the metabolic versatility of microorganisms and the efficiency of inorganic solar energy solar energy capture devices to drive the reduction of CO2 into biofuels. In the near future, this could lead to industrial-scale applications.

The principle of hybrid photosynthesis states that solar energy is captured by inorganic sunlight absorbers before its usage by biological catalysts for driving CO2 reduction as they can couple different types of inorganic solar energy capture devices such as solid-state photovoltaics, photoelectrodes, and photocatalyst nanoparticles. One strategy is to power a microbial electrosynthesis (MES) reactor with solid-state photovoltaics (PVs). Autotrophic microbes use reducing equivalents generated by an electrochemical reactor to reduce CO2 into biofuels. The most common configuration is an anode and cathode separated by an ion-exchange membrane and connected by an electric circuit with protons and electrons being generated by oxidation reactions. As electrons flow through the electric conduit from the anode to the cathode, while protons migrate through ion-exchange membranes, both are acquired by the autotrophic biocatalyst in the cathodic chamber where it reduces CO2. PV-driven MES reactors are connected to external wires to an autonomous solid-state PV cell as they provide a larger light absorption range from ultraviolet to near-infrared.

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