Fe-leaching induced surface reconstruction of Ni-Fe alloy on N-doped carbon to boost oxygen evolution reaction

Understanding the dynamic transformation process of the oxygen evolution reaction (OER) catalysts is of importance for their rational design. Here we first report that Fe-leaching could induce the electrochemical activation of strongly coupled Ni-Fe alloy on N-doped carbon composites to boost the OER performance. It is demonstrated that the leaching of unstable FeOOH mixed layer from the surface of FeNi3 alloy is responsible for the surface reconstruction and exposure of more active sites. Furthermore, the N-doped carbon, FeNi3 alloy, together with the accompanying generation of Fe-doped Ni(OH)2, synergistically promote the OER activity after fully activation. It is also verified that the high valent Ni species, pyridinic N and the metal-N species are the exact active centers and the fully activated catalyst Fe0.2Ni0.8/NC-600-a is among the best non-noble OER catalysts to date, which exhibits superior OER performance with a low overpotential (η20 = 290 mV) and small Tafel slope (76 mV dec−1). This study is helpful to understand the fundamentals of the Ni-Fe alloy catalysts and provides guidance to design advanced catalysts for water oxidation through in-situ electrochemical activation.