Fe induced nanostructure reorganization and electronic structure modulation over CoNi (oxy)hydroxide nanorod arrays for boosting oxygen evolution reaction

Abstract Ni- and Co-based (oxy)hydroxides are promising candidates for oxygen evolution reaction (OER), but their limited specific surface area and poor intrinsic conductivity lead to unsatisfied OER activity. Herein, a unique and universal self-template strategy has been developed to fabricate Fe-incorporated CoNi (oxy)hydroxide (Fe-CoNi-OH) nanosheet-assembled nanorod arrays toward OER. The reorganized nanosheet-assembled nanorod hierarchical structure induced by Fe incorporation exposes more active sites and facilitates mass transfer. Furthermore, Fe incorporation modifies the electron structure of CoNi (oxy)hydroxide (CoNi-OH), and enhances its electronic conductivity for rapid electron transport, thus intrinsically enhancing the OER activity. Consequently, the Fe-CoNi-OH possesses excellent OER activity with low overpotentials of 210, 248, 304, and 349 mV to achieve current densities of 10, 100, 500, and 1000 mA cm-2, respectively, along with a very small Tafel slope of 28.0 mV dec-1, which are superior to the CoNi-OH and benchmark RuO2. By paring the Fe-CoNi-OH anode with a CoP cathode, an outstanding alkaline electrolyzer has been constructed, which only requires cell voltages of 1.506 and 1.623 V to deliver current densities of 10 and 100 mA cm-2, respectively, and can stably work for 100 hours. This work provides a universal strategy to synthesize Fe-containing hierarchical nanostructured catalysts for energy conversion application.