Design and Synthesis of Cycloplatinated Polymer Dots as Photocatalysts for Visible-Light-Driven Hydrogen Evolution

Abstract

By mimicking natural photosynthesis, generating hydrogen through visible-light-driven splitting of water would be an almost ideal process for converting abundant solar energy into a usable fuel in an environmentally friendly and high-energy-density manner. In a search for efficient photocatalysts that mimic such a function, here we describe a series of cycloplatinated polymer dots (Pdots), in which the platinum complex unit is presynthesized as a comonomer and then covalently linked to a conjugated polymer backbone through Suzuki–Miyaura cross-coupling polymerization. On the basis of our design strategy, the hydrogen evolution rate (HER) of the cycloplatinated Pdots can be enhanced by 12 times in comparison to that of pristine Pdots under otherwise identical conditions. In comparison to the Pt-complex-blended counterpart Pdots, the HER of cycloplatinated Pdots is over 2 times higher than that of physically blended Pdots. Furthermore, enhancement of the photocatalytic reaction time with high eventual hydrogen production and low efficiency rolloff are observed by utilizing the cycloplatinated Pdots as photocatalysts. On the basis of their performance, our cyclometallic Pdot systems appear to be alternative types of promising photocatalysts for visible-light-driven hydrogen evolution.

Side-chain tuning in conjugated polymer photocatalysts for improved hydrogen production from water

“…Organic photocatalysts can be prepared from earth-abundant starting materials and offer advantages such as synthetic modularity and tunability of band gaps. [5][6][7] In particular, the recent development of linear conjugated polymer photocatalysts [8][9][10][11] has allowed for a more systematic fine-tuning of optical properties, band positions and other properties compared to carbon nitrides (C 3 N 4 ), 12,13 covalent organic frameworks (COFs), [14][15][16] covalent triazine-based frameworks (CTFs) [17][18][19] and conjugated microporous polymers (CMPs). [20][21][22] In most cases, these organic photocatalysts have not been shown to oxidize water.…”

Emulsion polymerization derived organic photocatalysts for improved light-driven hydrogen evolution

“…In addition, P10-e showed a very high visible light activity of 14.5 mmol h À1 g À1 along with greatly improved stability compared to the rst publications of photocatalytic active P-dots for hydrogen production, 34,36 as well as more recent cycloplatinated examples. 35 Some degree of aggregation of the emulsion particles appears to be benecial for optimal photocatalytic activity and the best-performing catalysts were mixtures of free nanoparticles and larger aggregates. This may, in part, be related to light absorption mechanisms and scattering effects.…”

“…P10-e was also tested at equivalent concentration to polymer dot photocatalysts reported in the literature [34][35][36] (13 mg mL À1 ) Table 1).…”

“…31,32 One approach to tailoring the morphology of organic photocatalysts is to prepare alkylated, solution-processable, conjugated polymers, which can be processed aer synthesis into thin lms 33 or nanoparticles. 34,35 In particular, conjugated polymer nanoparticles based on dialkyl-uorene-co-benzothiadiazole polymers were reported to give very high initial hydrogen evolutions rates (HERs) of up to 50 mmol g À1 h À1 . 34,36 The high initial HERs for the nanoparticles are, presumably, a result of the surface-tovolume ratio of the nanoparticles, which were prepared by antisolvent precipitation to give particle diameters in the range 20-100 nm.…”

Hydrophilic Conjugated Materials for Photocatalytic Hydrogen Evolution

“…Introduction of metal complex into the backbone of conjugated polymer is also an effective method to design novel polymer photocatalyst with improved photocatalytic performance. Tseng et al [38] synthesized cycloplatinated polymer (PFTFQÀ PtPy15, Scheme 3). After covering with PSÀ PEGÀ COOH, PFTFQÀ PtPy15 dots can be dispersed into water and form a homogenous solution.…”