Identification and Design of Active Sites on Photocatalysts for the Direct Artificial Carbon Cycle

Abstract

ConspectusImitating the natural carbon cycle, the utilization of the carbon-based greenhouse gases (i.e., carbon dioxide (CO2) and methane (CH4)) from the atmosphere as the carbon feedstocks for valuable fuel and chemical production represents a prospective strategy for achieving the sustainable development of human society. In light of this, photocatalytic CO2/CH4conversions, which can directly harvest solar energy for the production of valuable fuels and chemicals, show gigantic potential for closing the loop of the artificial carbon cycle. In the past several decades, immense progress has been made in this field, showing its practical feasibility. However, the photocatalytic conversion efficiency and selectivity of such reactions remain discouraging. Considering that the photocatalytic reaction is intimately related to the surface catalytic reaction on the active sites of the photocatalysts, the active site design has been proven to be effective for optimizing photocatalytic performance, yet the lack of effective techniques for the identification of the active sites, which is normally at the molecular level, greatly limits its potential in photocatalysis. Fortunately, with the rapid expansion in the field of materials science, a large number of advanced characterization techniques have been developed, equipping the materials scientist and chemist with powerful tools for unveiling the mask of the active sites on the photocatalysts. Concomitantly, the active site design for the photocatalysts has undergone a revival. Today, the identification and design of active sites have emerged as hot topics in catalysis and are expected to push forward development in the field of the artificial carbon cycle.Herein, we highlight the recent progress of our research group in the identification and design of active sites for the direct artificial carbon cycle. We begin by giving an introduction to the advantages of the direct artificial carbon cycle over the indirect artificial carbon cycle. Then, we systematically describe the concept of active sites and requirements for the active sites toward highly efficient and selective photocatalytic CO2/CH4conversion. Subsequently, we present an overview of the currently available characterization techniques and tools for identifying the active sites on the photocatalysts. Furthermore, we outline our group's endeavor in designing the active sites for photocatalytic CO2/CH4conversion. Finally, we conclude this Account by offering some comments on the current challenges and future perspectives in this field. We foresee that this Account not only summarizes the recent work of our group in this field but also can facilitate the development of the direct artificial carbon cycle.