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Identifying Co-catalysts for Photocatalysis

Research group from the University of Science and Technology of China develop an optimized platinum surface charge state as a co-catalyst for photocatalysis.

Photocatalysis is the conversion of solar energy into chemical energy, it has been recognized to be a very promising solution to the current energy and environmental issues. The performance of the photocatalytic system depends largely on the surface charge state of active sites – the co-catalyst – as the Schottky junction between photosensitizer and co-catalyst facilitates charge transfer between them and finally to reactant molecules, promoting the adsorption and activation of the latter.

In contrast to the existing reports regarding co-catalysts, such as the development of non-noble metal, particle size and distribution control, exposed crystal facets and their interface contact with photosensitizers, the regulation on surface charge state of co-catalysts by changing their microstructures provides vast opportunities for boosting photocatalysis, yet remains extremely rare.

In this research, Dr Jiang’s research group from the University of Science and Technology of China has achieved the goal of optimizing platinum surface charge state via the control of bimetallic palladium-platinum microstructure and platinum coordination environment.

The bimetallic core-shell-structured palladium-platinum nanoparticles have been in situ fabricated and stabilized by a photosensitive and representative metal-organic framework (MOF). The microstructure of the palladium-platinum co-catalyst can be precisely controlled from core-shell to single-atom alloy, during which platinum coordination environment changes, by precisely and simply tuning the platinum content.

Given the different working functions of palladium and platinum, the charge between palladium and platinum is redistributed, accompanied by platinum coordination environment change, thus achieving the surface charge state regulation of platinum sites.

As a result, all palladium-platinum/MOF present excellent photocatalytic hydrogen production activity due to the electron-rich Pt sites benefited from charge redistribution effect. Moreover, the optimized palladium-platinum/MOF composite with single-atom alloy co-catalyst, which features the most electron-rich platinum, exhibits an exceptionally high photocatalytic hydrogen production activity, far surpassing its corresponding counterparts.

This is the first report on single-atom alloy co-catalyst toward photocatalysis. It provides the design strategy and synthetic protocol for the fabrication of single-atom alloy catalysts and opens up a new avenue to single-atom alloy-based photocatalysis. In addition, as an alternative to the classical Schottky junction strategy, this work introduces a novel approach to charge state optimization by regulating the co-catalyst microstructure (especially the coordination environment control), toward enhanced photocatalysis. [APBN]