"Electrocatalysts play an inevitable role in many applications including energy storage, energy conversion, and biosensing. The state-of-the-art noble metal-based electrocatalysts have long been used in full water splitting, non-enzymatic glucose sensing, and supercapacitors. However, scarcity and high cost of noble metals restrict utilization of such electrocatalysts in large-scale implementations. Transition metal-based electrodes have been considered as a potential solution to address these drawbacks as well as to enhance the electrocatalytic performance. In this work, applicability of non-oxidic transition metal based electrocatalysts is evaluated. Transition metal chalcogenides are expected to have high catalytic performance owing to their facilitated electron cloud delocalization on the transition metal site as well as enhanced covalency in the lattice due to the low anion electronegativity. To examine this theory, CoNi2Se4 is studied for its application in full water splitting. This catalyst shows an excellent electrocatalytic activity with low overpotential of 160 mV @ 10 mA cm−2 for OER. CoNi2Se4-rGO on Ni foam has also been employed as an electrocatalyst for the direct oxidation of glucose. A high sensitivity of 18.89 mA mM−1 cm−2 at low applied potential of 0.35 V vs. Ag|AgCl is achieved. For the same application, we investigated Ni3Te2. With electrodeposition method, a high glucose detection sensitivity of 41.615 mA cm−2 mM−1 is reported. We also fabricated a hydrothermally synthesized Ni3Te2 with a sensitivity of 35.213 mA cm−2 mM−1. Finally, we examined NiCo2Se4/rGO for its application in supercapacitors and achieved a high specific capacitance of 2038.55 F g−1 with a high energy density and power density of 67.01 W h kg−1 and 903.61 W kg−1, respectively"--Abstract, page iv.