The Transformation and Storage of Solar Energy: Progress Towards Visible-Light Induced Water Splitting

Abstract

The sun is a plentiful source of clean, renewable power, and the direct conversion of solar to chemical energy is a desirable goal. The collective efforts of the Bernhard group to develop molecular catalytic systems for visible-light water splitting are reviewed. Combinatorial synthesis and high-throughput screening techniques enabled the development of a series of photosensitizers with a wide range of photophysical and electrochemical properties. Parallel evaluation of the iridium(III) photosensitizers in photocatalytic water reduction systems utilizing cobalt-, platinum-, or rhodium-based water reduction catalysts resulted in systems that exhibited more than 5000 turnovers with quantum yields of 34% and turnover frequencies of 500 hr?1. For the complementary water oxidation system, the catalysts based on cyclometallated iridium complexes are robust and tunable, which allows for the rapid study of water oxidation reactions through targeted ligand modification.

Direct α‐Arylation of Ethers through the Combination of Photoredox‐Mediated CH Functionalization and the Minisci Reaction

“…Irradiation of photoredox catalyst Ir[dF(CF 3 )ppy] 2 (dtbbpy)PF 6 ( 1 ) using visible light from a household light bulb at room temperature will produce a long-lived (2.3 μs) photoexcited state, *Ir III [dF(CF 3 )ppy] 2 (dtbbpy)PF 6 ( 2 ). [14] Given that the resulting *Ir III species is a strong reductant (E 1/2 IV/*III = −0.88 V vs. SCE in 2:1 MeCN:H 2 O), [12,15] we expected it to be capable of reducing the persulfate anion ( 3 ) [16] to afford Ir IV [dF(CF 3 )ppy] 2 (dtbbpy)PF 6 ( 4 ), sulfate dianion and the sulfate radical anion ( 5 ). We presumed that the desired α-oxyalkyl radical ( 7 ) could then be generated via a HAT event between the dialkyl ether ( 6 ) and sulfate radical anion.…”

Molecular systems for light driven hydrogen production

“…[124][125][126][127][128] When these complexes were initially analysed for their emission energy, molar absorptivity, and excited state lifetime, P6a-c and P12a-c (Fig. 7) stood out as having long-lived excited states.…”

Recent Advances in Photoredox‐Mediated Radical Conjugate Addition Reactions: An Expanding Toolkit for the Giese Reaction

“…Chemists can tune the photophysical and electrochemical properties of photoredox catalysts. [5] Moreover,p hotoredox-mediated processes are as amenable to picomole-scale reactions for high-throughput screening [21] as they are to [d] See ref. [26].…”