Jo Seung Geun, Kim Chung-Soo, Kim Sang Jun, Lee Jung Woo
Department of Materials Science and Engineering, Pusan National University, Busan 46241, Korea.
Analysis & Certification Center, Korea Institute of Ceramic Engineering & Technology, Jinju 52851, Korea.
Nanomaterials (Basel). 2021 Dec 13;11(12):3379. doi: 10.3390/nano11123379.
Efficient water electrolysis is one of the key issues in realizing a clean and renewable energy society based on hydrogen fuel. However, several obstacles remain to be solved for electrochemical water splitting catalysts, which are the high cost of noble metals and the high overpotential of alternative catalysts. Herein, we suggest Ni-based alternative catalysts that have comparable performances with precious metal-based catalysts and could be applied to both cathode and anode by precise phase control of the pristine catalyst. A facile microwave-assisted procedure was used for NiO nanoparticles anchored on reduced graphene oxide (NiO NPs/rGO) with uniform size distribution in ~1.8 nm. Subsequently, the Ni-NiO dual phase of the NPs (A-NiO NPs/rGO) could be obtained via tailored partial reduction of the NiO NPs/rGO. Moreover, we demonstrate from systematic HADDF-EDS and XPS analyses that metallic Ni could be formed in a local area of the NiO NP after the reductive annealing procedure. Indeed, the synergistic catalytic performance of the Ni-NiO phase of the A-NiO NPs/rGO promoted hydrogen evolution reaction activity with an overpotential as 201 mV at 10 mA cm, whereas the NiO NPs/rGO showed 353 mV. Meanwhile, the NiO NPs/rGO exhibited the most excellent oxygen evolution reaction performance among all of the Ni-based catalysts, with an overpotential of 369 mV at 10 mA cm, indicating that they could be selectively utilized in the overall water splitting. Furthermore, both catalysts retained their activities over 12 h with constant voltage and 1000 cycles under cyclic redox reaction, proving their high durability. Finally, the full cell capability for the overall water electrolysis system was confirmed by observing the generation of hydrogen and oxygen on the surface of the cathode and anode.
高效水电解是实现基于氢燃料的清洁可再生能源社会的关键问题之一。然而，电化学水分解催化剂仍有几个障碍有待解决，即贵金属成本高和替代催化剂的高过电位。在此，我们提出了一种镍基替代催化剂，其性能与贵金属基催化剂相当，并且通过对原始催化剂进行精确的相控制，可应用于阴极和阳极。采用简便的微波辅助方法制备了尺寸均匀分布在~1.8 nm的负载于还原氧化石墨烯上的NiO纳米颗粒（NiO NPs/rGO）。随后，通过对NiO NPs/rGO进行定制的部分还原，可以得到NP的Ni-NiO双相（A-NiO NPs/rGO）。此外，我们通过系统的高角度环形暗场-能谱仪（HADDF-EDS）和X射线光电子能谱（XPS）分析表明，在还原退火过程后，金属Ni可以在NiO NP的局部区域形成。实际上，A-NiO NPs/rGO的Ni-NiO相的协同催化性能促进了析氢反应活性，在10 mA cm时过电位为201 mV，而NiO NPs/rGO的过电位为353 mV。同时，NiO NPs/rGO在所有镍基催化剂中表现出最优异的析氧反应性能，在10 mA cm时过电位为369 mV，表明它们可选择性地用于全水解。此外，两种催化剂在恒压和循环氧化还原反应下1000次循环中均保持活性超过12 h，证明了它们的高耐久性。最后，通过观察阴极和阳极表面氢气和氧气的产生，证实了全水解系统的全电池性能。
