Some of the biggest energy corporations in the U.S. and China are teaming up to search for "clean coal" technology that extracts more energy and reduces carbon emissions. Duke Energy and Southern Co. are collaborating with Chinese firms to make coal more efficient and friendly to the environment. "There's a perception that the U.S. leads in this technology and China lags," said Armond Cohen, executive director of the Clean Air Task Force. "That's not so. In some key areas, China is more advanced. There's a lot to share."