Highly Efficient PEM Water Electrolyser with Noble Metal Loading Less Than 0.2 Mg/cm2

Abstract

The high loading of noble metal is considered as one of the main barriers for cost-effective PEM water electrolyser. To reduce the loading of Iridium in anode, advanced OER catalyst and catalyst layer with enhanced activity, stability and lower noble metal loading must be developed. In this work, to improve utilization of Ir in anode, supported catalyst was prepared. W-doped TiO2 (W-TiO2) was developed as a conductive support for dispersing Ir active sites, then disordered IrOx nanoparticles with higher OER activity was loaded on the oxide support to form composite catalyst. With the benefits of high surface area of W-TiO2, the particle size of IrOx can be reduced to about 1nm and thus increase the number of active sites. Structure disordered IrOx nanoparticles can further enhance the OER activity due to the optimized oxidation state of Ir and large number of hydroxyl groups. The Ir mass activity of composite catalyst shows 7-8 times improvement than commercial IrO2, and stability maintains the same. The degradation mechanism of the obtained catalyst was also explored by identical location TEM (ILTEM), the dissolution of oxide support and detachment of Ir was considered as the main reason, besides no obviously passivation of support was observed. Finally, MEA with ultra-low noble metal loading was successfully prepared by conventional CCM method. The total noble metal loading of MEA can be reduced to 0.2mg/cm2 (Ir in anode: 0.11mg/cm2, Pt in cathode: 0.085mg/cm2), and water electrolyser still achieved 1.613V@1A/cm2 (75% LHV) and almost 400h stable operation under 1 A/cm2, suggesting good stability of supported catalyst and new MEA. Figure 1