Interlocked Regulation of Surface Poisoning and Ion Diffusion Enabled by Tungsten Integration and Holey Graphene Oxide Support for Ammonia Oxidation

Abstract

The rising consideration of ammonia as a viable fuel has propelled the research on exploring the feasibility of commercializing direct ammonia fuel cells (DAFCs). However, DAFCs at present have poor efficiency caused by the sluggish ammonia oxidation reaction (AOR) kinetics and surface poisoning of the catalyst. This work is tackling the issues associated with the anodic part of the DAFCs by developing an electrocatalyst, i.e., Pt_0.76Ir_0.21W_0.03/HGO-13. The intrinsic pores of Holey Graphene Oxide (HGO) play a decisive role in enhancing the metal–support interactions, along with effectively mitigating flooding and mass-transport limitations during device testing. The oxyphilic W acts as a competitive OH^– reservoir, reducing OH^– poisoning on the PtIr active sites, which further boosts the AOR activity through OH^– mobilization by the spillover mechanism. The theoretical investigation of Pt_0.76Ir_0.21W_0.03/HGO-13 reveals the electron redistribution among Pt, Ir, and W, thereby modulating the NH_x and N adsorption and mitigating active-site poisoning. Also, the 2–3 atomic % of the W incorporation creates better nanointerface formation with PtIr than bulk W. Electrochemical half-cell analysis shows a better onset potential of 0.37 V and a superior peak current density of 76.1 A g^–1 (Pt_0.76Ir_0.21W_0.03/HGO-13) compared to the benchmark systems (Pt/C and PtIr/C). When employed in DAFCs, the Pt_0.76Ir_0.21W_0.03/HGO-13-based electrode exhibits a peak power density (PPD) of 90 mW cm^–2, outperforming the standard PtIr/C (54.8 mW cm^–2), clearly augmenting the synergistic modulations between the active sites and engineered porous support achieved in the present system.