Hierarchical Porous Ni3S4 with Enriched High-Valence Ni Sites as a Robust Electrocatalyst for Efficient Oxygen Evolution Reaction - Wan, Kai (Katholieke Universiteit Leuven. Department of Materials Engineering) ; Luo, Jiangshui (Katholieke Universiteit Leuven. Department of Materials Engineering) ; Zhou, Chen (Katholieke Universiteit Leuven. Department of Materials Engineering) ; Zhang, Ting (Institut Català de Nanociència i Nanotecnologia) ; Arbiol i Cobos, Jordi (Institut Català de Nanociència i Nanotecnologia) ; Lu, Xihong (Sun Yat-Sen University) ; Mao, Bing-Wei (Xiamen University) ; Zhang, Xuan (Katholieke Universiteit Leuven. Department of Materials Engineering) ; Fransaer, Jan (Katholieke Universiteit Leuven. Department of Materials Engineering)