“…Nowadays, the non-noble metal materials based on 3d transition metals, have been widely investigated and became the most potential alternatives for the noble metal catalysts attributed to its good availability, low price, environmental friendliness and relatively high activity. Several kinds of catalysts such as transition metal oxides [20][21][22][23][24][25][26][27], hydroxides [3,10,[28][29][30][31], phosphates [32,33] and sulfides [34][35][36] have been explored. In addition, the layered double hydroxides (LDH), which are composed of positively charged metal hydroxide layers with intercalated anions, have been regarded as potential catalysts for OER.…”