Non-platinum-based electrocatalysts for high performance acidic hydrogen evolution reactions in proton exchange membrane water electrolysis
Wenxia Xu, Dan Zhang, Tiantian Wang, Jianping Lai, Lei Wang
Abstract
To replace Pt for economical and scalable H 2 O to H 2 conversion in proton exchange membranes (PEM) water electrolysis , efforts are being made to find cost-effective catalysts that delicately co-ordinate key parameters such as high mass activity and long durability. We found that by engineering the small size (<5 nm) of RuMo bimetallic nanoparticles (NPs) on carbon nanotube (CNT) with a strong metal-support interaction (SMSI) effect, we could obtain Mo 2.8 -Ru@CNT- 2.8 catalysts with optimal activity and stability in acidic HER (Mo amount is 2.8 wt% and NPs size is about 2.8 nm). Experimental and theoretical studies reveal that reducing the size to about 2.8 nm can simultaneously obtain the optimal Gibbs free energy of H intermediate adsorption and the bonding energy between Ru-Ru/Ru-Mo, which contribute to the improvement of the catalytic activity and stability of Mo 2.8 -Ru@CNT- 2.8 . In addition, Mo doping can greatly increase the formation energy of Ru vacancies, which contribute to the improvement of the catalytic stability of Mo 2.8 -Ru@CNT- 2.8 . Specially, the optimized Mo 2.8 -Ru@CNT- 2.8 catalyst represent an advance in mass activity (4.4 A mg −1 Ru ) compared to commercial Pt/C catalysts (3.1 A mg −1 Ru ) and high per-site activity (32.7 s −1 ) under acidic conditions while remaining the excellent stability. At the same time, Mo 2.8 -Ru@CNT- 2.8 as a cathode in the proton exchange membrane (PEM) water electrolyser exhibits excellent cell voltages with a Ru loading of 0.06 mg Ru cm −2 (1.7 V to 1 A cm −2 ), 0.12 times that of commercial Pt/C with a Pt loading of 0.5 mg Pt cm −2 (1.74 V up to 1 A cm −2 ), and maintains long-term stability for 700 h at 1 A cm −2 .