Data-Driven Investigation of Tellurium-Containing Semiconductors for CO2 Reduction: Trends in Adsorption and Scaling Relations

Abstract

Light-assisted conversion of CO₂ into liquid fuels is one of several possible approaches to combating the rise of carbon dioxide emissions. Unfortunately, there are currently no known materials that are efficient, selective, or active enough to facilitate the photocatalytic CO₂ reduction reaction (CO₂RR) at an industrial scale. In this work, we employ density functional theory to explore potential tellurium-containing photocathodes for the CO₂RR by observing trends in adsorption properties arising from over 350 *H, 200 *CO, and 110 *CHO surface-adsorbate structures spanning 39 surfaces of 11 materials. Our results reveal a scaling relationship between *CHO and *H chemisorption energies and charge transfer values, while the scaling relation (typically found in transition metals) between *CO and *CHO adsorption energies is absent. We hypothesize the scaling relation between *H and *CHO to be related to the lone electron located on the bonding carbon atom, while the lack of scaling relation in *CO we attribute to the ability of the lone pair on the C atom to form multiple bonding modes. We compute two predominant orbital-level interactions in the *CO-surface bonds (either using s or p orbitals) in addition to bonding modes involving both σ and π interactions using the Crystal Orbital Hamiltonian Population analysis. We demonstrate that bonds involving the C s orbital are more chemisorptive than the C p orbitals of CO. In general, chemisorption trends demonstrate decreased *H competition with respect to *CO adsorption and enhanced *CHO stability. Finally, we uncover simple element-specific design rules with Te, Se, and Ga sites showing increased competition and Zn, Yb, Rb, Br, and Cl sites showing decreased competition for hydrogen adsorption. We anticipate that these trends will help further screen these materials for potential CO₂RR performance.

Figure 1

Electronic binding energy of CHO in relation to both (a) CO and (b) H on various tellurium-containing semiconducting surfaces. The minimum energy for each surface is plotted—the optimal site for chemisorption. Transition metal surfaces scaling relations for FCC (100), (111), and (211) are included for comparison. Additionally, a light orange dotted line demarcates where CHO formation is in equilibrium with CO formation, from the CHE model (detailed calculations in Supporting Information). Many materials show increased chemisorption of CHO over CO, especially in comparison to transition metal scaling relationships. A linear relationship can be observed between the H and CHO adsorption energies across the studied tellurium-containing materials (slope of 0.72, an intercept of −1.71, an R² value of 0.86, a p-value of 9.07 × 10^–6, and RMSD of 0.44 eV). There is no clear correlation between CO and CHO adsorption energies.

Figure 2

Crystal Orbital Hamiltonian Population Analysis (COHP) between (a) C from CO and nearby Yb atom for CO bonding exhibiting π bonding interactions and having a stronger chemisorptive bond, (b) C from CO and nearby Yb and Te atoms for CO bonding exhibiting no π bonding interactions and having a weaker chemisorptive bond, and (c) C from CHO and nearby Yb atom for an on-top adsorption site. The π interactions result from a summation of the p_x-p_x, p_y-p_y, -p_x, -p_y, and d_xz-p_x interactions and the σ interactions from any s orbital interaction as well as -p_z, and p_z-p_z interactions. In COHP, the area of the curves are proportional to the number of electrons in the system. All the systems represented above consist of the same number and types of atoms, and thus same number of electrons.

Figure 3

Gibbs free energy of adsorption for CO and H on various surfaces of tellurium-containing semiconductors. Scatter points indicate the minimum of the CO and H adsorption energy on each surface, while error bars indicate the range of adsorption energies on each surface. The points are color-coded by cleavage energy, where purple denotes the most stable surfaces, and yellow denotes the least stable ones. The vertical red line and blue horizontal line indicate the equilibrium Gibbs free energies of adsorption for CO and H, respectively. Most data points are close to, but to the left of, the CO equilibrium line indicating a weak attraction of the corresponding surfaces to CO. A few sites disfavor CO adsorption. While most CO binding energies fall within a narrow range of values (−0.25 to 0.75 eV), H binding energies are spread over a broader range (−1.5 to 2.5 eV). Points above the blue line denote surfaces where *H adsorption is not favored and which might therefore present lower competition from the HER reaction, facilitating the CO₂RR. The points near or below the blue line represent surfaces that are expected to be promising HER catalysts or catalysts poisoned by *H adsorption.

Figure 4

Trends in the coordination number of surface adsorption site and the Gibbs free energy of adsorption for *H.

Figure 5

Charge transfer data for CO, H, and CHO adsorbates computed using the DDEC6 method. Positive values indicate a transfer of charge to the adsorbate from the surface, while negative values indicate a transfer of charge from the adsorbate to the surface. The plotted points represent the mean of the charge transfer on all sites for each surface, and the statistical bars indicate the range of charge transfer values across all sites for each surface. The points are color-coded by the mean charge transfer between all sites on that surface and the CHO adsorbate. Data points which are left black and not colored according to *CHO charge transfer colorbar denote less stable surfaces for which *CHO adsorption calculations were not attempted due to their increased computational cost.

Figure 6

Bonding strength by the predominant carbon orbital in CO as calculated by LOBSTER. When carbon forms a bond with the s orbital, the bond tends to be stronger than when it forms bond with the p-orbital.