Unconventional bi-vacancies activating inert Prussian blue analogues nanocubes for efficient hydrogen evolution

Prussian blue analogues (PBA) have been explored as electrocatalyst for the hydrogen evolution reaction, however, they suffer from poor electrical conductivity and blocked active sites and thus usually operate at overpotentials drastically above thermodynamic requirement. Herein, we report a creation of unconventional anion (cyano group) and cation (cobalt) bi-vacancies to boost CoFe-PBA for HER through a rapid tannic acid (TA) etching strategy. The combined experimental and theoretical investigations indicate that the introduction of bivacancies would be favorable to exposure of accessible active sites, optimizing the electron density of CoFe PBA, and lowering the reaction energy barrier. As a result, the TA-etched CoFe PBA nanocubes supported on nickel foam (NF) (CoFe-PBA@TA/NF) exhibit outstanding HER catalytic activity with an overpotential of only 86 mV at 10 mA cm-2, which is not only significantly lower than bare PBA supported on NF (158 mV), but also comparable to the commercial Pt/C catalyst.

Automated summary

The introduction of unconventional anion and cation bivacancies has been shown to enhance the hydrogen evolution reaction catalytic activity of CoFe-PBA through a rapid tannic acid etching strategy. The resultant TA-etched CoFe-PBA nanocubes exhibit outstanding HER catalytic activity with an overpotential of only 86 mV at 10 mA cm-2, comparable to commercial Pt/C catalyst.