Catalyst mediates energy-efficient proton transport for reversibility
(PHYSorg.com Chemistry)

When it comes to solar power, storing electricity as fuel would let that energy work on dark or stormy days. The challenge is creating a catalyst that can push the reactions to produce a fuel, such as hydrogen, and later break the fuel to release the energy. Mother Nature does this every day in tiny microorganisms, such as those that make up pond scum. These enzymes work in both directions, reversibly, at room temperature and pressure without added energy.