Modelling materials for solar fuel synthesis by artificial photosynthesis; predicting the optical, electronic and redox properties of photocatalysts

Abstract

In this mini-review, we discuss what insight computational modelling can provide into the working of photocatalysts for solar fuel synthesis and how calculations can be used to screen for new promising materials for photocatalytic water splitting and carbon dioxide reduction. We will extensively discuss the different relevant (material) properties and the computational approaches (DFT, TD-DFT, GW/BSE) available to model them. We illustrate this with examples from the literature, focussing on polymeric and nanoparticle photocatalysts. We finish with a perspective on the outstanding conceptual and computational challenges.

Tailor‐Made Photoconductive Pyrene‐Based Covalent Organic Frameworks for Visible‐Light Driven Hydrogen Generation

“…Within different electrolytes this observation follows a Nernstian dependence indicating the validity of this technique (see Figures S25 and S26, Supporting Information): [30] With a change of the electrolyte phosphate buffer (pH = 7) to H 2 SO 4 (pH = 0) all energy levels drop significantly, following the chemical potential of the electrolyte (pH). We therefore conclude that the absolute levels of the CB ex are the main criteria to distinguish between the hydrogen evolution activity of those three COFs, which is in agreement with the electrochemical measurements: Excited electrons in the CB of A-TEBPY-COF have an increased thermodynamic driving force [31] for hydrogen evolution compared to A-TENPY-COF and A-TEPPY-COF (0.8 eV against 0.5 and 0.4 eV, respectively, see Figure 5a). VB levels are extrapolated by subtraction of the optical bandgap of the corresponding system.…”

“…VB and CB ex energies derived by quantum-chemical calculations on PBE0-D3/def2-TZVP (see the Supporting Information for details) level of theory show a reasonable match with the photo electrochemically derived energy levels (see Figure 5a orange lines). To investigate possible intermediate species during photo catalysis, we have devised a general photoexcitation scheme for the three COFs (see Figures S46 and S47, Supporting Information): [11,31] After excitation the exciton can either be quenched oxidatively or reductively, i.e., it can follow a radical cation or a radical anion pathway. 1.94, 1.92, and 1.91 eV for B, N, and P, respectively).…”

A High-Throughput Screening Approach for the Optoelectronic Properties of Conjugated Polymers

“…These calcu-lations use the COSMO 52,53 solvation model to approximate the dielectric environment of a polymer chain (e.g., at a polymer−water interface, ε r 80.1, or within the polymer bulk, ε r 2.0). As in our previous work, 39,54,55 the (TD)DFT calculations use the B3LYP 56−59 density functional and the DZP 60 basis-set. The absorption spectra of the polymer models are approximated by vertical singlet excitations, calculated using (TD)B3LYP/DZP.…”

Considerations of Trends in Heterogeneous Photocatalysis. Correlations between Conduction and Valence Band Energies with Bandgap Energies of Various Photocatalysts

“…Using well‐known data published for the complex (ternary) oxides, the search for new trends in the behavior of the E CB = f (E bg ) and the E VB = f (E bg ) dependences opens up the potential for the development of new VLA photocatalysts. It is clear that the feasibility of new desired trends can be estimated a priori using a modern theoretical analysis of the electronic structure of the targeted semiconductors . In this regard, it should be noted that the new trends in E CB and E VB behavior versus bandgap energy E BG have been established for CaBi 6 O 10 , Sr 2 Bi 2 O 5 , Sr 3 Bi 2 O 6 , and Sr 6 Bi 2 O 11 , i. e. for bismuth (Bi) and alkali earth metals (Ca, Sr) containing ternary oxides.…”