Harry B. Gray of the California Institute of Technology discusses the challenge of using chemistry to harness solar energy for sustainable fuel. The goal is to convert energy-poor molecules into energy-rich ones using sunlight, replacing fossil fuels with solar fuels like hydrogen or methanol. Efficient catalysts made from abundant, cheap materials are needed, as current ones like platinum are too rare. Nature uses proteins and metals to activate molecules, but biological systems degrade easily. Researchers are developing bioinspired materials to mimic enzymes for water splitting. Inorganic materials like metal oxides and sulfides are also being explored for water oxidation and reduction. The Solar Fuel Center for Chemical Innovation is working on nanorod catalysts to split water into hydrogen and oxygen. While progress has been made, efficient, large-scale water splitters from Earth-abundant materials are still a challenge. Gray envisions solar reactors that could produce fuels, electricity, and clean water, using atmospheric components and seawater. He believes that with fundamental chemical research, humanity can start repaying the environmental debt from past resource use. The article highlights ongoing research and the potential for solar fuel technology to meet future energy needs.Harry B. Gray of the California Institute of Technology discusses the challenge of using chemistry to harness solar energy for sustainable fuel. The goal is to convert energy-poor molecules into energy-rich ones using sunlight, replacing fossil fuels with solar fuels like hydrogen or methanol. Efficient catalysts made from abundant, cheap materials are needed, as current ones like platinum are too rare. Nature uses proteins and metals to activate molecules, but biological systems degrade easily. Researchers are developing bioinspired materials to mimic enzymes for water splitting. Inorganic materials like metal oxides and sulfides are also being explored for water oxidation and reduction. The Solar Fuel Center for Chemical Innovation is working on nanorod catalysts to split water into hydrogen and oxygen. While progress has been made, efficient, large-scale water splitters from Earth-abundant materials are still a challenge. Gray envisions solar reactors that could produce fuels, electricity, and clean water, using atmospheric components and seawater. He believes that with fundamental chemical research, humanity can start repaying the environmental debt from past resource use. The article highlights ongoing research and the potential for solar fuel technology to meet future energy needs.