A series of cobalt bis(benzenedithiolate) complexes with varying benzenedithiolate (general abbreviation: bdt(2-)) ring substitutions (S2C6X42-) were prepared and adsorbed on inexpensive electrodes composed of (a) reduced graphene oxide (RGO) electrodeposited on fluorine-doped tin oxide (FTO) and (b) highly ordered pyrolytic graphite (HOPG). The catalyst adsorbed electrodes are characterized by X-ray photoelectron spectroscopy. Catalyst loading across the ligand series improved notably with increasing halide substitution [from 2.7 x 10(-11) mol cm(-2) for TBA[Co(S2C6H4)(2)] (1) to 6.22 X 10(-10) mol cm(-2) for TBA[Co (S2C6Cl4)(2)] (3)] and increasing ring size of the benzenedithiolate ligand [up to 3.10 X 10(-9) mol cm(-2) for TBA[Co(S2C10H6)(2)] (6)]. Electrocatalytic analysis of the complexes immobilized on HOPG elicits a reductive current response indicative of dihydrogen generation in the presence of mildly acidic aqueous solutions (pH 2-4) of trifluoroacetic acid, with overpotentials of around 0.5 V versus SHE (measured vs platinum). Rate constant (k(obs)) estimates resulting from cyclic voltammetry analysis range from 24 to 230 s(-1) with the maximum k(obs) for TBA[Co(S(2)C(6)H(2)C1(2))(2)] (2) at an overpotential of 0.59 V versus platinum. Controlled-potential electrolysis studies performed in 0.5 M H2SO4 at -0.5 V versus SHE show impressive initial rate constants of over 500 s(-1) under bulk electrolysis conditions; however, steady catalyst deactivation over an 8 h period is observed, with turnover numbers reaching 9.1 x 10(6). Electrolysis studies reveal that halide substitution is a central factor in improving the turnover stability, whereas the ring size is less of a factor in optimizing the long-term stability of the heterogeneous catalyst manifolds. Catalyst deactivation is likely caused by catalyst desorption from the electrode surfaces.