Abstract: An electrolyzer cell (10) for the electrolysis of water comprises a cathode (12) of generally tubular configuration within which is disposed an anode (16) separated from the cathode (12) by a separation membrane (14) of generally tubular configuration which divides the electrolyte chamber (15) into an anode sub-chamber 15a and a cathode sub-chamber (15b). An electrolyzer apparatus (36) includes an array (38) of individual cells (10)across each of which an electric potential is imposed by a DC generator (40) via electrical leads (42a, 42b). Hydrogen gas generated within cells (10) from electrolyte (18) is removed via hydrogen gas take-off lines (20) and hydrogen manifold line (21). By-product oxygen is removed from cells (10) by oxygen gas take-off lines (22) and oxygen manifold line (23). The electrolyzer apparatus (36) may be configured to operate either batchwise or in a continuous electrolyterecycle operation to produce high purity hydrogen at high pressure, e.g.