Chen, Jiangyue, Li, Hao, Fan, Chuang, Meng, Qingwei, Tang, Yawen, Qiu, Xiaoyu, Fu, Gengtao, Ma, Tianyi. Wiley; 2020. Dual single-atomic Ni-N4 and Fe-N4 sites constructing Janus Hollow Graphene for selective oxygen electrocatalysis.