Experimental design for studying electrocatalytic hydrogen oxidation on VN₂-based single-atom catalysts driven by theoretical screening

Development of alkaline fuel cells is considerably impeded by the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline media. While platinum remains the benchmark catalyst, its high cost and scarcity necessitate exploring efficient nonprecious metal alternatives. This study designs a research-oriented computational experiment that transforms frontier research achievements in single-atom catalysis into teachable content. By focusing on the theoretical screening of two-dimensional VN₂-based single-atom catalysts (TM-VN₂), the study aims to identify potential high-performance materials and cultivate students’ computational thinking and ability to solve complex problems in energy materials science.

The experiment was conducted using density functional theory calculations within the Materials Studio software environment. A series of transition metal (TM = Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Ru)–doped VN₂ models was constructed by substituting a single vanadium atom with a transition metal atom. The research methodology followed a systematic screening workflow. First, thermodynamic stability was evaluated by calculating the cohesive energy of the pristine VN₂ layer and the formation energy of the doped systems. Second, electrochemical stability under alkaline conditions was assessed by computing the oxidation potential of the anchored metal atoms to ensure resistance against dissolution. Following the stability screening, the adsorption behaviors of key reaction intermediates (H* and OH*) were investigated to identify the active sites and determine the corresponding adsorption free energies. Finally, the catalytic activity for the HOR was evaluated by mapping the reaction free energy diagrams.

The comprehensive screening results demonstrated that Fe-VN₂ exhibits outstanding thermodynamic and electrochemical stability. The iron atom is stably anchored at the center of the nitrogen rectangle, effectively modulating the charge distribution. The differential charge density analysis revealed substantial electron transfer from the iron atom to the nitrogen ligands, indicating the formation of strong ionic bonds that stabilize the structure. Fe-VN₂ forms a dual-functional active site where hydrogen atoms preferentially adsorb on neighboring nitrogen sites, while the hydroxyl groups adsorb on the iron site. The adsorption free energies for both H* and OH* on Fe-VN₂ were calculated to be extremely close to the theoretically optimal values (approximately 0.02 eV and −0.10 eV, respectively). Consequently, Fe-VN₂ has the lowest energy barriers among all the investigated systems for the elementary steps involving the reaction between hydrogen molecules and adsorbed hydroxyl groups, as well as the reaction between adsorbed hydrogen and hydroxyl groups. The rate-determining step analysis confirmed that the energy barrier for the H* + OH* reaction was only 0.14 eV, which is notably lower than that of other candidates. Volcano plot analysis confirmed that the activity descriptor for Fe-VN₂ lies at the peak of the activity curve, indicating better catalytic performance than other transition metal dopants.

This study successfully identified Fe-VN₂ as a highly promising nonplatinum anodic catalyst for alkaline fuel cells. The designed experiment provides a comprehensive simulation of a real-world research workflow, effectively enhancing students’ understanding of the relationship between electronic structures and catalytic performance. By engaging in this computational exercise, students can greatly improve their capabilities in scientific innovation and theoretical analysis within the context of new energy materials.