As we seem to be burning fossil fuels at an alarming rate,it was obvious we had to turn to a new source of energy.Scientists predict the world will be out of oil reserves by around 2050 which has led us to focus on renewable sources of energy.Tesla’s electric car was one such innovation which provided a step towards the use of green energy.A large number of solar panels are being used to generate electricty by placing them above houses,lamposts etc.Windmills are set up to harness the power of wind energy.Again these sources of energy can only be used at certain locations plus cost a lot to set up which causes problems.Now finally coming to the main problem:what can replace fossil fuels?Well the answer might just lie in green fuels.Green fuel,which is also called biofuel, is a type of fuel obtained from plants and animal materials, believed by some to be more environmentally friendly than the widely-used fossil fuels that power most of the world. In the desperate search for alternative energy sources, green fuel has evolved as a possible fueling option as the world drains its fossil fuel resources. An alternative that has been long talked about is to use that green electricity to kick CO2 up the energy ladder. Carbon dioxide, the combustion by-product that comes out of power plant smokestacks and is getting too plentiful in the Earth’s atmosphere, is at the bottom of the hill when it comes to carbon-based fuels. As energy goes, it’s spent. If you could add some energy to it, though, you could convert CO2 into carbon compounds that are fuels, not a waste product. In chemical parlance, it’s called reducing CO2 when you convert it to less-oxidized forms of carbon, all of which have actual fuel value. Some single-carbon molecules to aim for would include (in increasing energy content) carbon monoxide (CO), methanol, and methane.Any of these could be stored for a cloudy or windless stretch of time, and in most situations a lot more readily than electricity. Methane is the primary component of natural gas, for which there is already plenty of existing infrastructure. Methanol, or wood alcohol, is a close relative of ethanol, or grain alcohol, and is routinely used as a liquid fuel. Carbon monoxide might seem unusual in this context, but it has chemical value as a fuel, both in and of itself and as a precursor to other fuels. The trick, of course, is to be able to do the CO2 reduction economically. That means not just efficiently converting the electrical energy into chemical energy, but also making the device that does the job a cost-effective one. However this might be possible due to Xiao-Dong Zhou, an associate professor of chemical engineering at the University of South Carolina, is part of a team that is working on a sustainable approach to harnessing renewable energy. They have developed potentially inexpensive catalysts that efficiently convert CO2 to CO in an electrochemical cell. As a starting point for making the catalysts, they used as a model carbon nanotubes, which are made purely of carbon atoms. But in making their catalysts for CO2 reduction, they departed from the carbon-only motif by sprinkling in a few nitrogen atoms to create a different kind of geometric and electronic structure.The resulting “nitrogen-doped carbon nanotubes” proved to be adept at reducing CO2 to CO, and the team reports that the catalysts are more stable than metal-based catalysts reported in the literature for the same reaction. We might be taking a step towards a cleaner future.