Anti-poisoned oxygen reduction by the interface modulated Pd@NiO core@shell

摘要

The methanol (CH3OH) crossover in direct methanol fuel cells is very poisonous to cathodic noble metal electrocatalysts, which usually leads to serious degradation of electrocatalytic performance. However, most focus of present research has been concentrated on the persistent pursuit of enhancing the sluggish ORR reactions while the pivotal methanol crossover has been left out generally. The "reactivity and anti-poison" dilemma has been approached by many surface engineering including the development of new membrane with low methanol permeability or assemble layered structures. As the notable structure-dependent performance in catalytic reaction, our work has proposed Pd@NiO core@shell as an interface engineering approach that can significantly inhibit the CO species adsorption while preserving the ORR reactivity, which can also exhibit superior stability even in poisoning circumstances. Herein, we report a series of unique Pd@NiO-x/C with controlled interface structure to overcome the activity and anti-poisoning issues of oxygen reduction reaction (ORR), where the optimized Pd@NiO/C exhibits a high activity of 0.24 A mg(-1), excellent tolerance over the CH3OH/CO poisoning as well as superior stability even in the practical poisoning circumstances, all which are far better than the commercial Pt/C and Pd/C. DFT calculations reveal that the excellent ORR performance with effective methanol tolerance become superior with core@shell interfacial engineering. With effective modulations, the generalized interfacial d-band-offset can be achieved for counteracting the ORR barriers with extra-high current density. The simultaneously high activity and excellent anti-poisoning features of the Pd@NiO nanostructure make it a practically potential electrocatalyst for fuel cell and beyond.