Ion-etched zeolitic imidazolate framework (ZIF) derived transition metal phosphides with a thin carbon shell as high-performance trifunctional catalyst for oxygen reduction, oxygen evolution and hydrogen evolution reactions

Oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have wide application prospects in metal-air battery, water electrolysis and other green energy fields. High-performance catalysts with these three catalytic activities at the same time usually contain two or more precious metals (Pt, Ru, Ir). These noble metal catalysts have disadvantages of high cost and poor stability. In this study, a high-performance trifunctional non-noble metal catalyst is synthesized via ion etching transition metal-doped ZIF-8 precursor and subsequent phosphating through pyrolysis. Thanks to gentle etching without heating, it preserves the shape and chemical composition of the precursor meanwhile creates numerous folds on the surface that facilitate contact between the active site and electrolyte. The strong interfacial coupling during etching and the in-situ-grown carbon shell during pyrolysis give the catalyst a large amount of highly active sites and extremely strong stability. Therefore, the catalytic performances exceed most of the reported single, bifunctional and trifunctional catalysts. Especially, the catalyst electrocatalyzes ORR at the highest half-wave potential of 0.898 V and OER with a very small overpotential of 330 mV at 10 mA cm^-2. In addition, it is used to assemble Zn-air battery and water splitting devices, demonstrating much more superior performances than commercial benchmark catalysts.