Recently, the focus has shifted towards ternary copper oxides because of their enhanced flexibility in property tuning compared to binary counterparts, gaining attention as potential photocathodes for PEC reduction reactions. Earth-abundant, stable, and environmentally friendly bismuth oxide materials have been the sought-after goal for developing photocatalytic applications for environmental pollutant degradation, water splitting, and noxious gas reduction. The p-type semiconducting behavior is represented in copper oxides. Consequently, combining copper and bismuth oxides to form ternary oxides such as copper bismuth oxide CuBi 2 O 4 (CBO) yields p-type conductivity. Here, the alloying decreases the rate of CBO self-reduction by guiding the electrons away from the Cu 3d-orbitals. Thereby, the reduced electronic band gap achieves efficient solar absorption. Another promising candidate for photocathode materials is CuFeO 2 (CFO) containing Cu + ions. Among cuprous delafossites, CFO possesses the smallest band gap (1.1 -1.5 eV), consists of earth-abundant elements, and can be prepared by various scalable and low-cost deposition methods. In most works, only the structural and electronic properties of the bulk phases of CBO and CFO have been investigated. However, the photocathode's properties are predominantly influenced by their surface properties and so are the PEC reaction processes themselves. Therefore, the main focus of this work is to study the surface properties of different CBO and CFO surface orientations, predicting stable terminations and their electronic features. The article is structured as follows. First, we will provide a concise overview of our computational methodology. Subsequently, we will explore the electronic properties of CBO's and CFO's bulk phases and the conditions required for the thermodynamic stability of the CBO and CFO bulk compounds, considering a range of chemical potentials for their constituent elements. Next, we will discuss the electronic structure of diverse surfaces and different terminations, using density of states (DOS) and Bader charge analysis. Finally, we will analyze the stability of the surfaces and their terminations using ternary surface phase diagrams.