The cobalt(III) macrocyclic Schiff-base complex, [Co(III)(CR)Cl]ClO(4) (CR = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.1]-heptadeca-1(17),2,11,13,15-pentaene), is an active catalyst for the electrocatalytic proton reduction to generate dihydrogen in both acetonitrile and 100% aqueous solution (at -0.57 and -0.85 V vs SCE, respectively), using p-cyanoanilinium tetrafluoroborate and acetic acid as proton sources, respectively. Bulk electrolysis confirmed that dihydrogen is produced with >90% Faradaic yields and >50 TON in both solvents. [Co(III)(CR)Cl(2)]ClO(4) also catalyzes photo-driven (lambda > 390 nm) hydrogen production in aqueous acetonitrile at TON of 180 (not optimized), using [Ir(III)(ppy)(2)(bpy)]PF(6) as the photosensitizer, triethanolamine (TEOA) as the sacrificial donor and acetic acid as the proton source. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.