Oxidation of any hydrocarbon is an electrochemical reaction - an exchange of electrons between fuel and oxidizer. In an "ordinary" oxidation reaction, the electron exchange is completely internal, and the only product is heat. That heat is converted to electric power through a series of mechanical means, e.g., heating water to steam, using the expansion of stem to push a turbine, using the turbine in a magnetic field to create electricity. It wastes a lot of the energy of the original oxidation reaction. In a solid oxide fuel cell, the electron exchange is captured through an external circuit, making it significantly more efficient as a generator of electricity. This is why, for example, Google reports using half of the natural gas for the same electrical output.