Influence of d-state density and chemistry of transition metal cluster selenides on electrocatalysis

Abstract

Catalytic studies were carried out on two important electrochemical reaction processes, hydrogen evolution and molecular oxygen reduction in acid medium comparing the transition metal cluster compounds Mo 4Ru 2Se 8, Mo 2Re 4Se 8, Mo 6Se 8, and the Mo metal. Our results show that during the hydrogen evolution reaction, in the course of catalytic charge transfer with the cluster, the hydrogen species solely interacts with individual metal atoms. Molecular oxygen, on the other hand, during oxygen reduction interacts with the cluster as a whole. We propose that the important factors involved in such a process are the high density of d states and the chemistry of the elements. The former factor can be significantly improved by going from the pure metal to transition metal cluster compounds and mixed transition metal compounds. The second factor can be considered by incorporating adequate transition metal atoms into the cluster. Since less catalytic elements for the reduction of oxygen in acid medium (e.g., Mo, Ru, Re) behave like highly catalytic elements (e.g., Pt, Ir) when incorporated into the cluster structure, these experimental results probably indicate a new route for tailoring efficient catalysts from more abundant transition elements.