"Less is more” is a concept proposed by Ludwig Mies van der Rohe who was an architect known for his minimalism design style. Can such a simplicity concept be applied to the field of materials science? Most recently, the research group led by Prof. XIONG Yujie completed a work demonstrating that the “less is more” design could enable hydrogen evolution reaction (HER) electrocatalysts superb performance. This progress has been published in Angew. Chem. Int. Ed. 2014, 53, 12120 and highlighted on the back cover of journal entitled “Less is more”.
HER electrocatalyst design highlighted on the back cover of Angewandte Chemie
To meet the increasing energy and environmental demands, various approaches have been developed to produce hydrogen – an energy source with high energy density and minimal pollution. Electrocatalytic HER represents a highly important process for hydrogen generation, constituting reversible hydrogen fuel cell technology. Despite tremendous efforts on alternative materials, Pt is still the most efficient electrocatalyst for the HER. Reducing the Pt usage is always the ultimate goal for electrocatalyst design to achieve cost-effective hydrogen production.
To address this grand challenge, the researchers have designed a class of Pt-Pd-graphene stack structures and developed methodology for precisely controlling Pt layer thickness, producing a series of hybrid structures with tunable Pt shells. These unique hybrid structures allow correlating the Pt thickness with HER performance. It turns out that the HER activity is boosted along with the reduction of Pt thickness, reaching the best performance – current density of 791 mA cm-2 at -300 mV and Tafel slope of 10 mV decade-1 (significantly superior to commercial Pt/C catalyst) when the thickness shrinks to the regime within 4 atomic layers. Their collaborators from Prof. Jun Jiang’s research group elucidate by theoretical simulations that the difference in work functions of Pt and Pd results in surface polarization on the Pt surface, tuning its charge state for hydrogen reduction. Meanwhile, the supporting graphene provides two-dimensional channels for efficient charge transport, improving the HER activities. This work opens up possibilities of reducing Pt usage while achieving high HER performance, and provides fresh insights into rationally designing the hybrid catalysts from a different perspective.
This work was supported by 973 Program, NSFC, Recruitment Program of Global Experts and CAS Hundred Talent Program.
(HFNL)
