On the Design of Donor–Acceptor Conjugated Polymers for Photocatalytic Hydrogen Evolution Reaction: First-Principles Theory-Based Assessment

A set of fluorene-based polymers with a donor–acceptor architecture has been investigated as a potential candidate for photocatalytic hydrogen evolution reaction. A design protocol has been employed based on first-principles theory and focusing on the following properties: (i) broad absorption spectrum to promote a higher number of photogenerated electron–hole pairs, (ii) suitable redox potentials, and (iii) appropriate reaction thermodynamics using the hydrogen-binding energy as a descriptor. We have found that the polymers containing a fused-ring acceptor formed by benzo­(triazole-thiadiazole) or benzo­(triazole-selenodiazole) units display a suitable combination of such properties and stand out as potential candidates. In particular, PFO-DSeBTrT (poly (9,9′-dioctylfluorene)- 2,7-diyl-alt-(4,7-bis­(thien-2-yl)-2-dodecyl-benzo-(1,2c:4,5c′)- 1,2,3-triazole-2,1,3-selenodiazole)) has an absorption maximum at around 950 nm for the highest occupied molecular orbital–lowest unoccupied molecular orbital transition, covering a wider range of solar emission spectrum, and a reduction catalytic power of 0.78 eV. It also displays a calculated hydrogen-binding free energy of ΔGH = 0.02 eV, which is lower in absolute value than that of Pt (ΔGH ≈ −0.10 eV). Furthermore, the results and trends analysis provide guidance for the rational design of novel photo-electrocatalysts