Redox shuttle mechanism enhances photocatalytic H2 generation on Ni-decorated CdS nanorods

Abstract

Photocatalytic conversion of solar energy to fuels, such as hydrogen, is attracting enormous interest, driven by the promise of addressing both energy supply and storage. Colloidal semiconductor nanocrystals have been at the forefront of these efforts owing to their favourable and tunable optical and electronic properties as well as advances in their synthesis. The efficiency of the photocatalysts is often limited by the slow transfer and subsequent reactions of the photoexcited holes and the ensuing high charge recombination rates. Here we propose that employing a hydroxyl anion/radical redox couple to efficiently relay the hole from the semiconductor to the scavenger leads to a marked increase in the H2 generation rate without using expensive noble metal co-catalysts. The apparent quantum yield and the formation rate under 447 nm laser illumination exceeded 53% and 63 mmol g(-1) h(-1), respectively. The fast hole transfer confers long-term photostability on the system and opens new pathways to improve the oxidation side of full water splitting.

Enhanced hydrogen evolution rates at high pH with a colloidal cadmium sulphide–platinum hybrid system

“…While the former is slightly lower compared to the H 2 evolution in the presence of SO 3 2− hole scavenger (5 mmol h −1 g −1 ), 15,19 a remarkable six-fold increase in H 2 generation rates for pH 13 and 14 in comparison with pH 11 and 12 follows the recently reported trend for Ni-decorated CdS nanorods. 22 This strong increase in efficiencies also favourably compares to the previously reported CdS/ZnSe/Pt hybrid system by Acharya et al (0.2 mmol h −1 g −1 ) 18 and the CdS/Pt system published by Wang et al (13.8 mmol h −1 g −1 ), 17 and is ascribed to a fast removal process of the photohole. Instead of the slower direct photohole transfer to TEA at low pH, 23 the OH − ions at high pH effectively promote the scavenging of photohole transfer by forming • OH radicals.…”

Sub-10 nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production

“…Moreover, high QY of 1.74% can be obtained on T-1 sample under monochromatic light at l ¼ 420 nm. To our knowledge, these are the highest QYs ever reported for stable oxide semiconductors under comparable conditions 18,53 , although they are still lower than other systems, for example, CdSe nanocrystals capped with dihydrolipoic acid 54 and Ni-decorated CdS nanorods 55 . In addition to its remarkable photocatalytic activity, T-1 exhibits very good stability as a photocatalyst.…”

Recent Progress in Semiconductor‐Based Nanocomposite Photocatalysts for Solar‐to‐Chemical Energy Conversion

“…Reproduced with permission. [44] Copyright 2014, Nature Publishing Group. 48 h, which was much more efficient than the system modified with a mononuclear Ru(II) complex.…”