Function-oriented design of robust metal cocatalyst for photocatalytic hydrogen evolution on metal/titania composites

Dong Wang,Xue-Qing Gong

doi:10.1038/s41467-020-20464-x

Abstract

While the precise design of catalysts is one of ultimate goals in catalysis, practical strategies often fall short, especially for complicated photocatalytic processes. Here, taking the hydrogen evolution reaction (HER) as an example, we introduce a theoretical approach for designing robust metal cocatalysts supported on TiO2 using density functional theory calculations adopting on-site Coulomb correction and/or hybrid functionals. The approach starts with clarifying the individual function of each metal layer of metal/TiO2 composites in photocatalytic HER, covering both the electron transfer and surface catalysis aspects, followed by conducting a function-oriented optimization via exploring competent candidates. With this approach, we successfully determine and verify bimetallic Pt/Rh/TiO2 and Pt/Cu/TiO2 catalysts to be robust substitutes for conventional Pt/TiO2. The right metal type as well as the proper stacking sequence are demonstrated to be key to boosting performance. Moreover, we tentatively identify the tunneling barrier height as an effective descriptor for the important electron transfer process in photocatalysis on metal/oxide catalysts. We believe that this study pushes forward the frontier of photocatalyst design towards higher water splitting efficiency.

Highlights

While the precise design of catalysts is one of ultimate goals in catalysis, practical strategies often fall short, especially for complicated photocatalytic processes
These findings imply that each metal layer at the interface is unique and may exhibit distinct catalytic behaviors compared with other layers or bulk metals
We adopted our previous approach of calculating the intrinsic electron transfer (IET) energy[28], defined by the energy change of moving an excess electron from TiO2 bulk to supported metal particles in the absence of surface adsorbates, to compare the electron transferring ability among candidate metals

Summary

Introduction

While the precise design of catalysts is one of ultimate goals in catalysis, practical strategies often fall short, especially for complicated photocatalytic processes. Since the interface bridges the oxide and metals, its structure as well as the metal-support interaction (MSI)[14], on one hand controls the adhesive contact strength and the electron transfer process, and on the other hand affects the surface reaction activity owing to the induced charge redistributions[15,16,17,18] Many modification techniques, such as morphology engineering[19,20], particle size control[21,22], alloying[23,24] etc., are all able to alter the interface properties and the photocatalytic performance (albeit uncertainty in promotion or not). Moffat and colleagues[23] reported the precise control of the structure and quantity of deposited metals even in the range of monolayer level, whereas Chen and Bent[33] realized the area-selective

Methods

Results

Conclusion