Clean Donor Oxidation Enhances the H₂ Evolution Activity of a Carbon Quantum Dot–Molecular Catalyst Photosystem

Abstract

Carbon quantum dots (CQDs) are new-generation light absorbers for photocatalytic H2 evolution in aqueous solution, but the performance of CQD-molecular catalyst systems is currently limited by the decomposition of the molecular component. Clean oxidation of the electron donor by donor recycling prevents the formation of destructive radical species and non-innocent oxidation products. This approach allowed a CQD-molecular nickel bis(diphosphine) photocatalyst system to reach a benchmark lifetime of more than 5 days and a record turnover number of 1094±61 molH2 (molNi )(-1) for a defined synthetic molecular nickel catalyst in purely aqueous solution under AM1.5G solar irradiation.

Understanding metal–organic frameworks for photocatalytic solar fuel production

“…It is vital to understand the role of these sacrificial electron donors 78 such that we can replace them by recyclable electron donors. 79,80 Then, by combining this system with a water oxidation catalyst, sustainable solar fuel generation can be achieved. 27 Low charge mobility is another limitation in most photocatalytic MOFs.…”

CQD-Based Composites as Visible-Light Active Photocatalysts for Purification of Water

“…Carbon quantum dots have also been applied as visible-light photosensitizer for non-noble metal H 2 -evolution catalyst [24,60,68]. Martindale et al used CQDs as a photosensitizer to energize a nickel-based molecular catalyst, Ni-bis-(diphosphine) (NiP) to produce H 2 under visible-light irradiation [24,60].…”

“…Martindale et al used CQDs as a photosensitizer to energize a nickel-based molecular catalyst, Ni-bis-(diphosphine) (NiP) to produce H 2 under visible-light irradiation [24,60]. A proposed scheme of H 2 production in the homogeneous CQD-NiP system is presented in Figure 6(c).…”

“…Irradiation of photoluminescent CQDs with visible-light results in the direct transfer of photoexcited electrons to the catalyst NiP with subsequent reduction of aqueous protons to H 2 . The electron donor EDTA [60] or TCEP/EDTA [24] quenches the photogenerated holes in the CQDs. In a similar work, McCormick and coworkers [68] used a PVP-coated CQD as a photosensitizer for a nickel nanoparticle (NiNP) catalyst ( Figure 6(d)) to produce H 2 at a much higher quantum yield of 6%.…”

“…This relatively new material has attracted huge interest in many fields including, but not limited to, electrocatalysis [6], biosensing [7][8][9][10], bioimaging [11][12][13][14], chemical sensing [15], and nanomedicine [16], due to their unique tunable photoluminescence (PL) properties, chemical inertness, high water solubility, ease and low cost of fabrication and, more importantly, low toxicity. Additionally, CQDs have also attracted considerable interest in various photocatalytic applications-environmental remediation [17][18][19][20][21], water splitting to produce H 2 production [22][23][24][25][26][27], CO 2 conversion [28][29][30], and synthesis of chemicals [28][29][30][31][32][33]-because when coupled with a semiconductor photocatalyst, CQDs can provide with several advantages, including improved light harvesting ability, efficient usage of the full spectrum of sunlight, efficient charge carrier separation, stability, and hinder charge recombination. Figure 1 illustrates the various applications of CQDs in photocatalysis (left) and their competitive optical and structural properties during each photocatalytic procedure (right).…”