Stable Isolated Metal Atoms as Active Sites for Photocatalytic Hydrogen Evolution

Abstract

The process of using solar energy to split water to produce hydrogen assisted by an inorganic semiconductor is crucial for solving our energy crisis and environmental problems in the future. However, most semiconductor photocatalysts would not exhibit excellent photocatalytic activity without loading suitable co-catalysts. Generally, the noble metals have been widely applied as co-catalysts, but always agglomerate during the loading process or photocatalytic reaction. Therefore, the utilization efficiency of the noble co-catalysts is still very low on a per metal atom basis if no obvious size effect exists, because heterogeneous catalytic reactions occur on the surface active atoms. Here, for the first time, we have synthesized isolated metal atoms (Pt, Pd, Rh, or Ru) stably by anchoring on TiO2 , a model photocatalystic system, by a facile one-step method. The isolated metal atom based photocatalysts show excellent stability for H2 evolution and can lead to a 6-13-fold increase in photocatalytic activity over the metal clusters loaded on TiO2 by the traditional method. Furthermore, the configurations of isolated atoms as well as the originality of their unusual stability were analyzed by a collaborative work from both experiments and theoretical calculations.

The Power of Single‐Atom Catalysis

“…Hollow sites, each missing three carbon atoms, on graphene were thought to be ideal anchoring sites for single Ni atoms after calculation 11b. Recently, theoretical screening with the aim of finding robust anchoring sites for SACs have been reported intensively, for example, for graphene,22e TiN,22c BN,32 θ ‐Al 2 O 3 ,22b TiO 2 ,9b and various metal nanoparticles 10. In fact, robust anchoring of the single atom to the support is not enough to achieve the potential of SACs.…”

“…The research and applications of SACs are rapidly being extended. In 2014, Yang and co‐workers for the first time reported the use of SACs of M 1 /TiO 2 in photocatalytic hydrogen evolution,9b where M is an isolated atom of Pt, Pd, Rh, or Ru strongly anchored to the support. As novel photocatalysts, M 1 /TiO 2 illustrated not only excellent stability for H 2 evolution, but also a 6–13 fold increase in photocatalytic activity compared with the metal clusters loaded onto TiO 2 .…”

High‐Performance Ru1/CeO2 Single‐Atom Catalyst for CO Oxidation: A Computational Exploration

“…[2][3][4] Experimentally,s ignificant progress has been made on the synthesis and characterization of single-metala toms on variouss ubstrates, such as metal, [5] graphene, [6,7] zeolites and open metal-oxides upports. [8][9][10][11][12][13][14][15][16][17][18] Theoretically,t he catalytic activities toward CO oxidation of single-metal atom embedded on the graphene [19][20][21][22][23] or graphene oxide [24] or BN nanosheet [25][26][27] or metal oxides [12,16,[28][29][30] have been studied. Wang et al performed ab initio simulations to understand the reaction mechanism of CO oxidation over ceria-supported Au particles, andt hey found that in the presence of CO, an isolated AuÀCO speciese merges to catalyze CO oxidationw ith the adjacent interface oxygen and subsequently the isolatedAureintegrates back into the nanoparticle after the reactioni sc ompleted.…”

Cluster Size Effects of Platinum Oxide as Active Sites in Hydrogen Evolution Reactions

“…Further research on noble-metal-based cocatalysts is therefore essential in the development of an efficient photocatalytic system that can specifically suppress the undesirable H 2 oxidation reaction (HOR), while preserving efficient H 2 evolution rate under light irradiation.Recently, oxidized platinum (Pt d + ) cocatalysts, which have the capacity for suppressing HOR, have been found to be efficient for HER from solar water splitting. [13][14][15] However, their potential as active materials for photoreactions has only received sporadic attention. Recent advances in ligand-assisted loading methods have fostered a renewed interest in stabilizing the valence state of Pt species (that is, PtO); [13] the regulation of cluster sizes enables the control over their electronic and physical properties.…”