Improving the electrocatalytic activity of Fe/Co-8-16-4 graphyne through sulfur or phosphorus doping for water splitting

The advancement of clean energy technologies depends on the rational design of cost-effective single-atom catalysts capable of efficiently driving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here, we report for the first time sulfur (S) or phosphorus (P) doping of 8-16-4 graphyne (GY) decorated with single Fe or Co atoms to enhance electronic properties and catalytic activity for overall water splitting. Using density functional theory (DFT), we evaluate the stability, electronic structure, and HER/OER performance of TM-S 1 -GY, TM-S 2 -GY, TM-P 1 -GY, and TM-P 2 -GY (TM = Fe, Co). Doping modifies charge distribution, weakens OER intermediate adsorption, and improves HER by increasing active sites. Fe-S 1 -GY, Fe-P 1 -GY, and Co-P 1 -GY show superior bifunctional activity compared to undoped Fe-GY and Co-GY. Linear scaling relationships between ΔG HOO∗ and ΔG HO∗ , and between ΔG O∗ and ΔG HO∗ , confirm that OER activity can be predicted through these correlations. Exchange current density ( i 0 ) versus ΔG H∗ analysis indicates optimal HER activity for Fe-P 1 -GY (P), Fe-P 1 -GY (C1), and Co-P 1 -GY (C1). Volcano plot analysis further demonstrates that Co-S 1 -GY, Co-P 1 -GY, Co-S 2 -GY, and Fe-S 1 -GY exhibit outstanding OER efficiency. The work provides critical insights for rational design of bifunctional electrocatalysts, offering new opportunities in water-splitting applications. • Fe-P 1 -GY (C1), Fe-P 1 -GY (P), and Co-P 1 -GY (C1) with ΔGH∗ ≈ 0 eV are optimal for HER. • Co-S 1 -GY and Co-P 1 -GY show low OER overpotentials of 0.45 and 0.46 V. • Fe-P 1 -GY, Fe-S 1 -GY, and Co-P 1 -GY exhibit excellent bifunctional catalytic activity. • Doping S or P induces charge redistribution and improves HER/OER performance. • Scaling relations and volcano plots identify key descriptors for water splitting.