Daniel P. Sheehan, Beyond the Second Law of Thermodynamics: "These culminated in 2012-13 with a series of lab- oratory experiments that showed true second law breakdown.4 The demonstration was straightforward. A small, closed, high- temperature cavity contained two metal catalysts (rhenium and tungsten), which were known to dissociate molecular hydro- gen (H2) to different degrees (Figure 1). (Rhenium dissociates hydrogen molecules into atoms better than tungsten does; conversely, tungsten recombines hydrogen atoms back into hydrogen molecules better than rhenium.) Because the disso- ciation reaction (H2 - 2H) is endothermic (absorbs heat), and the recombination reaction (2H - H2) is exothermic (liberates heat), when hydrogen was introduced into the cavity, the rhenium surfaces cooled (up to more than 125 K) relative to the tungsten (Figure 2). Because the hydrogen-metal reactions were ongoing in the sealed cavity, the rhenium stayed cooler than the tungsten indefinitely. This permanent temperature difference--this steady-state nonequilibrium--is expressly for- bidden by the second law, not just because the system won't settle down to a single-temperature equilibrium, but because this steady-state temperature difference can, in principle, be used to drive a heat engine (or produce electricity) solely by converting heat back into work, which is a violation of one of the most fundamental statements of the second law (Kelvin- Planck formulation)."