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Carbon dioxide capture and utilization is a strategic technology for moving away from fossil‐C. The conversion of CO2 into fuels demands energy and hydrogen that cannot be sourced from fossil‐C. Co‐processing of CO2 and water under solar irradiation will have a key role in the long‐term for carbon‐recycling and energy products production. This article discusses the synthesis, characterization and application of the two‐phase composite photocatalyst, In2O3@g‐C3N4, formed by thermal condensation of melamine in the presence of indium(III)nitrate. The composite exhibits a n,n‐heterojunction between two n‐type semiconductors, g‐C3N4 and In2O3, leading to a more efficient charge separation. The composite has a flat band potential enabling it to effectively catalyze the reduction of CO2 in the gas phase to produce CO, CH4 and CH3OH. While the composite's overall photocatalytic efficiency is comparable to that of neat g‐C3N4, its ability to promote multielectron‐transfer and Proton Coupled to Electron Transfer (PCET) suggests that there is a potential for further optimization of its properties. The use of labelled 13CO2 has allowed us to clearly exclude that the reduced species are derived from the photocatalyst decomposition or the degradation of contaminants. [ABSTRACT FROM AUTHOR]

The photochemical and photoelectrochemical reduction of CO2 is a promising approach for converting carbon dioxide into valuable chemicals (materials) and fuels. A key issue is ensuring the accuracy of experimental results in CO2 reduction reactions (CO2RRs) because of potential sources of false positives. This paper reports the results of investigations on various factors that may contribute to erroneous attribution of reduced-carbon species, including degradation of carbon species contained in photocatalysts, residual contaminants from synthetic procedures, laboratory glassware, environmental exposure, and the operator. The importance of rigorous experimental protocols, including the use of labeled 13CO2 and blank tests, to identify true CO2 reduction products (CO2RPs) accurately is highlighted. Our experimental data (eventually complemented with or compared to literature data) underline the possible sources of errors and, whenever possible, quantify the false positives with respect to the effective conversion of CO2 in clean conditions. This paper clarifies that the incidence of false positives is higher in the preliminary phase of photo-material development when CO2RPs are in the range of a few 10s of μg gcat−1 h−1, reducing its importance when significant conversions of CO2 are performed reaching 10s of mol gcat−1 h−1. This paper suggests procedures for improving the reliability and reproducibility of CO2RR experiments, thus validating such technologies. [ABSTRACT FROM AUTHOR]

The enzymatic effectiveness in the reaction cascade that reduces CO2 to methanol in water at room‐temperature faces various constraints. One of the major challenges is the short life of costly enzymes: immobilization is used to make them more stable and recyclable. The comparative analysis of the several immobilization techniques reported in the literature is challenging due to the diverse reaction conditions (single enzyme test or pool of enzymes test) and experimental setups, as well as the high variability in the amount of enzymes and cofactor. In the present study, a comparison is presented among three different methods (co‐encapsulation into Ca–alginate beads, co‐absorption onto zirconium(IV) phosphate (ZrP) and covalent binding to dialdehydecellulose [DAC]) of co‐immobilization of the three dehydrogenases Fatedehydrogenase (DH), FaldDH, and alcohol dehydrogenase, used in equal amount and under the same experimental conditions, so to check at what extension the support and the immobilization method can influence the activity of the enzymatic pool. DAC is used for the first time to support the three DHs and results to be the best method of immobilization with respect to those used here, that also allows longer life on enzymes and repeated recycling of the supported enzymes, increasing the overall methanol production with respect to the free enzymes. [ABSTRACT FROM AUTHOR]