Unlocking the Catalytic Potential of TiO₂-Supported Pt Single Atoms for the Reverse Water–Gas Shift Reaction by Altering Their Chemical Environment

Abstract

Single-atom catalysts (SACs) often exhibit dynamic responses to the reaction and pretreatment environment that affect their activity. The lack of understanding of these behaviors hinders the development of effective, stable SACs, and makes their investigations rather difficult. Here we report a reduction–oxidation cycle that induces nearly 5-fold activity enhancement on Pt/TiO 2 SACs for the reverse water–gas shift (rWGS) reaction. We combine microscopy (STEM) and spectroscopy (XAS and IR) studies with kinetic measurements, to convincingly show that the low activity on the fresh SAC is a result of limited accessibility of Pt single atoms (Pt 1 ) due to high Pt–O coordination. The reduction step mobilizes Pt 1 , forming small, amorphous, and unstable Pt aggregates. The reoxidation step redisperses Pt into Pt 1 , but in a new, less O-coordinated chemical environment that makes the single metal atoms more accessible and, consequently, more active. After the cycle, the SAC exhibits superior rWGS activity to nonatomically dispersed Pt/TiO 2 . During the rWGS, the activated Pt 1 experience slow deactivation, but can be reactivated by mild oxidation. This work demonstrates a clear picture of how the structural evolution of Pt/TiO 2 SACs leads to ultimate catalytic efficiency, offering desired understanding on the rarely explored dynamic chemical environment of supported single metal atoms and its catalytic consequences.

Disordered, Sub-Nanometer Ru Structures on CeO2 are Highly Efficient and Selective Catalysts in Polymer Upcycling by Hydrogenolysis

“…This is supported by the results of X-ray photoemission spectroscopy (XPS) measurements (Figure e), which show that the binding energy of the Ru 3 d 5/2 peak shifts from 279.9 eV (close-to-metallic) on reduced 2 wt % Ru/CeO 2 to 280.4 and 280.5 eV (cationic) on reduced 0.25 and 0.125 wt % Ru/CeO 2 , respectively. Therefore, XANES and XPS are in close agreement, revealing that the Ru species with intriguing hydrogenolysis performances on low-loading Ru/CeO 2 are cationic, a character commonly observed with highly dispersed metal species on oxides. ,− …”

Plasma-Catalytic CO2 Hydrogenation over a Pd/ZnO Catalyst: In Situ Probing of Gas-Phase and Surface Reactions

“…The continuous consumption of fossil fuels has led to the rapid growth of CO 2 concentrations in the atmosphere, significantly contributing to climate change and global warming. CO 2 conversion and utilization is considered an important strategy to reduce CO 2 emissions while producing valuable fuels and chemicals for energy storage. − However, CO 2 is a very stable chemical, and thus, the conversion of CO 2 often requires high temperature and/or high pressure with the presence of a catalyst. Efficient, cost-effective, and selective reduction of CO 2 into synthetic fuels and chemical building blocks continues to be one of the greatest challenges in the 21st Century.…”

Recent Progress in Thermal Conversion of CO2 via Single‐Atom Site Catalysis

“…Reproduced under the terms of the Creative Commons CC BY license. [ 68 ] Copyright 2021, The Authors. Published by American Chemical Society.…”

“…Szanyi's group reported redispersion of Pt on TiO 2 substrate for rWGS. [ 68 ] As mentioned in CeO 2 part, chemical environment was the key factor to catalytic properties. A redox cycle was employed for Pt/TiO 2 and transferred the highly O‐coordinated Pt species to less coordinated ones with high accessibility (Figure 5e).…”

“…e) Schematic representation of the evolution of Pt/TiO 2 during the redox cycle. Reproduced under the terms of the Creative Commons CC BY license [68]. Copyright 2021, The Authors.…”