A hint from phosphine complex: The π back-bonding in cobalt-phosphorene composite enables enhanced electrocatalytic performance

Regulating the electronic structure of the metal electrocatalyst is fundamental for its performance optimizing. The electronic states of the active metal centers are highly dependent on their coordination environment, especially when bonding is formed. The π back-bonding can induce great electron density redistribution around metals, yet it is barely applied in electrocatalyst design. Herein we electrodeposited metallic cobalt on black phosphorus (BP) nanosheets, forming BP-Co with a unique π back-bonding on the interfaces. The BP-Co exhibited high electrocatalytic activity and stability for hydrogen evolution reaction in alkaline electrolyte. The electrochemical and spectroscopic characterizations demonstrated that the BP acted as σ donor and π acceptor to coordinate with electron-rich metallic Co, similar to the phosphine complex. The directional σ bond strengthen the relationship between BP and Co, while the non-directional π bond accelerated the in-plane electron transfer. The π back donation also decreased the oxophilicity of Co to make BP-Co resist the poison from oxygen species. This study can intrigue new thinking prospective for the electrocatalyst design.