A scientific illustration of the study, which appeared on the cover of the issue of ACS Catalysis that contained the paper. Image: Tokyo Tech, ACS Catalysis.
A scientific illustration of the study, which appeared on the cover of the issue of ACS Catalysis that contained the paper. Image: Tokyo Tech, ACS Catalysis.

The carbon dioxide (CO2) released into the atmosphere by fossil fuel burning is a leading cause of global warming. One way to address this growing threat is to develop CO2 reduction technologies that convert CO2 into useful chemicals, such as carbon monoxide (CO) and formic acid (HCOOH).

In particular, photocatalytic CO2 reduction systems use visible or ultraviolet light to drive CO2 reduction, much like how plants use sunlight to conduct photosynthesis. Over the past few years, scientists have reported many sophisticated photocatalysts based on metal-organic frameworks and coordination polymers (CPs). Unfortunately, most of these photocatalysts either require complex post-synthesis treatments and modifications, or are made from precious metals.

In a paper in ACS Catalysis, a Japanese research team reports a way to overcome these challenges. Led by Yoshinobu Kamakura and Kazuhiko Maeda at Tokyo Institute of Technology (Tokyo Tech), the team developed a new kind of photocatalyst for CO2 reduction, based on a CP containing lead–sulfur (Pb–S) bonds. Known as KGF-9, this novel CP possesses an infinite structure (–Pb–S–)n with properties unlike any other known photocatalyst.

For instance, KGF-9 has no pores or voids, meaning that it has a low surface area. Despite this, however, it achieved a spectacular photoreduction performance. Under visible-light irradiation at 400nm, KGF-9 demonstrated an apparent quantum yield (product yield per photon absorbed) of 2.6% and a selectivity of over 99% in the reduction of CO2 to formate (HCOO).

“These values are the highest yet reported for a precious metal-free, single-component, photocatalyst-driven reduction of CO2 to HCOO,” says Maeda. “Our work could shed light on the potential of nonporous CPs as building units for photocatalytic CO2 conversion systems.”

In addition to its remarkable performance, KGF-9 is easier to synthesize and use compared to other photocatalysts. Since the active Pb sites (where CO2 reduction occurs) are already ‘installed’ on its surface, KGF-9 does not require the presence of a cocatalyst such as metal nanoparticles or metal complexes. Moreover, it requires no other post-synthesis modifications to operate at room temperature and under visible light illumination.

The team at Tokyo Tech is already exploring new strategies to increase the surface area of KGF-9 and boost its performance further. As the first photocatalyst with Pb(II) as an active center, there is a good chance that KGF-9 will pave the way for more economically feasible CO2 reduction.

As the research team says: “We believe that our study provides an unprecedented opportunity for developing a new class of inexpensive photocatalysts for CO2 reduction consisting of earth-abundant elements.”

This story is adapted from material from Tokyo Institute of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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