Probing water–formate interactions on copper surfaces: A DFT approach to co-adsorption on Cu(111)

Understanding water’s role in stabilizing adsorbates on metal surfaces is key to improving catalytic systems. Using density functional theory (DFT), we investigated the co-adsorption of formate (HCOO) and water on Cu(111). Three formate geometries were evaluated: bidentate ($E_{\mathrm{ads}}=-0.82\mathrm{eV}$), monodentate via hydrogen ($E_{\mathrm{ads}}=-0.27\mathrm{eV}$), and monodentate via oxygen ($E_{\mathrm{ads}}=-0.24\mathrm{eV}$), with bidentate being the most stable. Co-adsorption with H${}_2$O enhances stability: bidentate formate shows interaction energies of $E_{\mathrm{int}}=-0.32\mathrm{eV}$ (one H${}_2$O) and $-0.53\mathrm{eV}$ (two H${}_2$O), while monodentate forms show much weaker stabilization. The approximate 0.20 eV increase in stability per added water molecule arises mainly from hydrogen bonding between water and formate oxygens. The enhanced stability in the two-water case arises from cooperative effects, where one H${}_2$O forms a hydrogen bond with the formate oxygen and the second H${}_2$O interacts weakly with the Cu surface. These results highlight water’s key role in stabilizing bidentate formate on Cu surfaces, reinforcing its thermodynamic preference in aqueous conditions.