An Overlooked Natural Hydrogen Evolution Pathway: Ni2+ Boosting H2O Reduction by Fe(OH)2 Oxidation during Low‐Temperature Serpentinization

Abstract Natural hydrogen (H 2 ) has gained considerable attentions as a renewable energy resource to mitigate the globally increasing environmental concerns. Low‐temperature serpentinization (<200 °C) as a typical water–rock reaction is a major source of the natural H 2 . However, the reaction mechanism and the controlling step to product H 2 remained unclear, which hinders the further utilization of natural H 2 . Herein, we demonstrated that the H 2 production rate could be determined by the Fe(OH) 2 oxidation during low‐temperature serpentinization. Moreover, the co‐existence of Ni 2+ could largely enhance the H 2 production kinetics. With the addition of only 1 % Ni 2+ , the H 2 production rate was remarkably enhanced by about two orders of magnitude at 90 °C. D 2 O isotopic experiment and theoretical calculations revealed that the enhanced H 2 production kinetics could be attributed to the catalytic role of Ni 2+ to promote the reduction of H 2 O.