Solar-to-Chemical Conversion

5 Chapter 11Table 11.1 Applied reduction potentials related to the N 2reduction [4,18]. Sources: Bazhenova et al. [4]; Chen et al.[18].Table 11.2 Performance summary of various heterojunctions for photocatalytic and photoelectrochemical N 2reduction.

6 Chapter 12Table 12.1 Structure parameters of MIL‐125‐NH 2, MIL‐125‐R7, and OPA/MIL‐125‐NH 2. Source: Kawase et al. [31]. © 2019, Royal Society of Chemistry.

7 Chapter 13Table 13.1 Reaction categories involved in photo‐mediated catalysis and related Gibbs free energy.Table 13.2 Hydrogen or methanol yield in methane steam reforming reaction using various photocatalysts.Table 13.3 Methane coupling reaction with photo‐assisted catalysis.

8 Chapter 14Table 14.1 Photocatalytic conversion of processed lignin in literatures. Source: Liu et al. [49]. © 2019, The Royal Society of Chemistry.Table 14.2 Photocatalytic conversion of cellulose in literatures. Source: Liu et al. [49]. © 2019, The Royal Society of Chemistry.

1 Chapter 2 Figure 2.1 Schematic of solar fuel feedstocks (CO 2, H 2O, and solar energy) and production path on‐site and/or transported to the solar refinery [4]. Figure 2.2 Schematic diagrams of (a) natural photosynthesis and (b) artificial photosynthesis based on molecular systems. Source: Liu et al. [9]. Figure 2.3 (a) Traditional catalytic processeson the surface of catalysts. (b) Classic photocatalytic paths over photocatalysts. Figure 2.4 A band‐gap diagram showing the different sizes of band gaps for conductors, semiconductors, and insulators. Figure 2.5 Proposed mechanism of photocatalytic reactions on semiconductor photocatalysts. Source: Ma et al. [16]. Figure 2.6 A schematic illustration of the energy correlation between semiconductor catalysts and redox couples in water. CB and VB denote a conduction band and a valence band, respectively. Source: Tu et al. [20]. Figure 2.7 (a) Yields of the products produced during the photocatalytic reduction of CO 2with H 2O and photoluminescence of various Ti/FSM‐16 photocatalysts. (b) Product distribution of CO 2photoreduction over 1‐TiO 2, 2–10 wt% imp‐TiO 2/Y‐zeolite, 3–1.0 wt% imp‐TiO 2/Y‐zeolite, 4‐ex‐TiO 2/Y‐zeolite, and 5‐Pt‐loaded ex‐TiO 2/Y‐zeolite. (c) Schematic mechanisms of the photocatalytic CO 2reduction with H 2O on TiO 2. Source: (a) Ikeuea et al. [23]; (b) Anpo et al. [22]; (c) From Anpo et al. [21]. © 1995 Elsevier. Figure 2.8 Schematic cycle for the photosensitized reduction of CO 2to CH 4. Source: Maidan and Willner [25]. Figure 2.9 (a) Calculated band structures and total density of states of BMO‐OVs. Absorptive formats of CO 2on BMO‐OVs (b) and BMO (c). CO 2reduction pathways on BMO‐OVs (d) and BMO (e). (f) The diagram of band positions. (g) CH 4production and the TCEN value for CO 2photoreduction over the BMO‐OVs and BMO during four hours visible‐light irradiation. (h) Typical time course of CO/CH 4generated over BMO‐OVs. Source: Yang et al. [30]. Figure 2.10 (a) Schematic illustration of the solar‐assisted production of methanol from CO 2and water through a three‐enzyme cascade. (b) Methanol production as a function of time in multienzymatic systems. (c) Photoelectrochemical production of methanol by TPIEC under various applied potentials under visible‐light illumination. (d) Methanol production of the TPIEC system in various multienzymatic systems with an external voltage of 0.8 V. Source: Kuk et al. [41]. Figure 2.11 (a) Mechanism for the reduction of CO 2by photocatalysis under visible light with a Ru complex and an N‐Ta 2O 5hybrid catalyst. (b) Turnover number for HCOOH formation from CO 2over various molecular systems as a function of irradiation time. (c) Schematic mechanism of visible‐light‐driven photocatalytic CO 2reduction over RuP/NS‐C 3N 4hybrids. (d) Time courses of photocatalytic CO 2reduction using RuP/NS‐C 3N 4‐PU0 and RuP/NS‐C 3N 4‐PU90 under visible light ( λ > 400 nm). Source: (a) Suzuki et al. [55]; (b) Sato et al. [55]; (c) Tsounis et al. [56]; (d) Tsounis et al. [56]. Figure 2.12 (a) Scheme of the photocatalytic CO 2reduction over CdS/(Cu–Na xH 2−xTi 3O 7) irradiated by light. (b) Gas evolution rates of C1–C3 hydrocarbons on CdS/(Cu–Na xH 2−xTi 3O 7) as well as the specific surface area, where the Na/Ti ratios were 0.093 (low), 0.143 (medium), and 0.507 (high). (c–e) Mass spectra of the formed hydrocarbons (methane, ethane, and propane) with the labeling of 13C. (f) Proposed elementary reaction mechanisms of photocatalytic CO 2conversion into hydrocarbons. Source: Park et al. [64]. Figure 2.13 Structures of CN before (a) and after (b) doping with carbon chains. (c) Electrochemical impedance spectroscopy (EIS) Nyquist plots under irradiation condition. Inset: Periodic on/off photocurrent response under visible‐light irradiation. (d) Comparison of the photocatalytic CO 2reduction rate of the samples with different amount of glycine, respectively. Source: Ren et al. [70]. Figure 2.14 (a) Gas production under six hours visible‐light irradiation of pure Cu 2O and Cl‐doped Cu 2O samples. (b) Mass spectrum from the 18O‐labeling H 2O isotope experiments of Cu 2O–Cl‐4. (c) Time‐dependent product evolution over Cu 2O–Cl‐4 under visible‐light irradiation. (d) Stability test of Cu 2O–Cl‐4. (e) Proposed reaction pathways of CO 2RR to CO and CH 4on Cl‐doped Cu 2O. Source: Yu et al. [83].

2 Chapter 3 Figure 3.1 The light‐dependent reactions of photosynthesis produce protons and electrons used in the conversion of CO 2to carbohydrates (CH 2O) and other organic compounds, while oxidation of these organic compounds (biomass, food, fuels) by respiration or combustion releases the stored solar energy to power the metabolism of non‐photosynthetic organisms and drive human technologies. Figure 3.2 Schematic membrane arrangement of enzymes involved in the light‐dependent reactions of oxygenic photosynthesis. Red arrows indicate the flow of electrons from the primary electron donor H 2O to the final electron acceptor NADP +aided by photoexcitation in photosystems II and I. Electron flow is tied to proton translocation across the membrane. The proton gradient created by accumulation of protons in the interior of the membrane powers the synthesis of ATP. Figure 3.3 Selected types of chlorophyll molecules encountered in natural photosynthesis. Figure 3.4 (a) Side and top view of the light‐harvesting complex LH2 from the purple bacterium R. acidophila 10050 (PDB: 1KZU [24]), showing bacteriochlorophyll a pigments in green and carotenoids (rhodopin glucoside) in orange. (b) Rod structure of c ‐phycocyanin from the phycobilisome light‐harvesting antenna of cyanobacterium T. vulcanus (PDB: 3O18 [25]). (c) Light‐harvesting complex II (LHCII) from pea (PDB: 2BHW [26]), showing Chl a pigments in dark green and Chl b in light green. Figure 3.5 Examples of synthetic approaches to multi‐chromophore arrays: (a) a nine‐porphyrin array unit comprising a central free‐base porphyrin core that acts as final acceptor and is surrounded by eight energy‐donating zinc porphyrins [43]. Source: Choi et al. [41] Figure 3.6 Simplified Z‐scheme of natural oxygenic photosynthesis, showing how two photons are used per electron flowing from the terminal donor (H 2O) to the terminal acceptor (NADP +) of the light‐dependent reactions. Figure 3.7 Photosystem II from T. vulcanus (PDB ID: 3WU2, a) and major redox‐active components within a PS‐II monomer involved in the main‐pathway electron transfer indicated with red arrows (b). Figure 3.8 The cycle of intermediate oxidation states of the oxygen‐evolving complex. Water is assumed to bind at the S 3state of the cluster and upon reconstitution of the S 0state. The S 4state is a postulated but unobserved transient intermediate that decays spontaneously to S 0with release of dioxygen. Figure 3.9 The Mn 4CaO 5cluster and its protein pocket in the dark‐stable S 1state as revealed by protein crystallography (PDB ID: 3WU2, a), and a scheme showing the commonly used labeling of the ions comprising the inorganic core. Figure 3.10 Proposed models for the inorganic core in the S 2state of the OEC, with the first coordination sphere mostly omitted for clarity. The different magnetic topologies of the two valence isomers, as expressed through the pairwise exchange coupling constants J ij(values shown in cm −1; J < 0 is antiferromagnetic coupling), lead to different total spin states and g values for the corresponding EPR signals. Figure 3.11 The S 2→ S 3transition according to Retegan et al. [191] and possible isovalent Mn(IV) 4components of the S 3state; the superscript “W” indicates binding of an additional water ligand. Figure 3.12 Two selected scenarios for the nature of the S 4state and OO bond formation from the computational literature: (a) formation of a Mn1(IV)‐oxyl group in the S 4state is followed by odd‐electron radical oxyl–oxo coupling [285], and (b) formation of a five‐coordinate high‐spin Mn4(V)‐oxo is followed by intramolecular nucleophilic coupling with concerted water binding [289]. Thick lines indicate direction of Jahn–Teller axes of Mn(III) ions. Figure 3.13 Reaction mechanism of RuBisCO proposed by Taylor and Andersson. Source: Taylor and Andersson [351].