Department of Material and Life Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency, Suita, Osaka 565-0871, Japan.
J Am Chem Soc. 2011 Oct 12;133(40):16136-45. doi: 10.1021/ja206079e. Epub 2011 Sep 16.
Photocatalytic hydrogen evolution with a ruthenium metal catalyst under basic conditions (pH 10) has been made possible for the first time by using 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh(+)-NA), dihydronicotinamide adenine dinucleotide (NADH), and Ru nanoparticles (RuNPs) as the photocatalyst, electron donor, and hydrogen-evolution catalyst, respectively. The catalytic reactivity of RuNPs was virtually the same as that of commercially available PtNPs. Nanosecond laser flash photolysis measurements were performed to examine the photodynamics of QuPh(+)-NA in the presence of NADH. Upon photoexcitation of QuPh(+)-NA, the electron-transfer state of QuPh(+)-NA (QuPh(•)-NA(•+)) is produced, followed by formation of the π-dimer radical cation with QuPh(+)-NA, [(QuPh(•)-NA(•+))(QuPh(+)-NA)]. Electron transfer from NADH to the π-dimer radical cation leads to the production of 2 equiv of QuPh(•)-NA via deprotonation of NADH(•+) and subsequent electron transfer from NAD(•) to QuPh(+)-NA. Electron transfer from the photogenerated QuPh(•)-NA to RuNPs results in hydrogen evolution even under basic conditions. The rate of electron transfer from QuPh(•)-NA to RuNPs is much higher than the rate of hydrogen evolution. The effect of the size of the RuNPs on the catalytic reactivity for hydrogen evolution was also examined by using size-controlled RuNPs. RuNPs with a size of 4.1 nm exhibited the highest hydrogen-evolution rate normalized by the weight of RuNPs.
首次在碱性条件（pH 10）下，使用 2-苯基-4-(1-萘基)喹啉翁离子（QuPh(+)-NA）、二氢烟酰胺腺嘌呤二核苷酸（NADH）和 Ru 纳米颗粒（RuNPs）分别作为光催化剂、电子供体和析氢催化剂，实现了 Ru 金属催化剂在碱性条件下的光催化产氢。RuNPs 的催化活性与市售 PtNPs 几乎相同。进行纳秒激光闪光光解测量以检查 QuPh(+)-NA 在 NADH 存在下的光动力学。在 QuPh(+)-NA 的光激发下，产生 QuPh(+)-NA 的电子转移态（QuPh(•)-NA(•+）），随后与 QuPh(+)-NA 形成π-二聚体自由基阳离子，[(QuPh(•)-NA(•+))(QuPh(+)-NA)]。NADH 向π-二聚体自由基阳离子的电子转移导致通过 NADH(•+)的去质子化和随后从 NAD(•)向 QuPh(+)-NA 的电子转移产生 2 当量的 QuPh(•)-NA。光生 QuPh(•)-NA 向 RuNPs 的电子转移甚至在碱性条件下也导致氢的产生。QuPh(•)-NA 向 RuNPs 的电子转移速率远高于氢的产生速率。还通过使用尺寸可控的 RuNPs 检查了 RuNPs 的尺寸对析氢反应催化活性的影响。粒径为 4.1nm 的 RuNPs 的氢析出率归一化到 RuNPs 的重量最高。
