I'm fairly inexperienced in chemistry so forgive me if this question is silly but, why is it not possible to convert a combustion reaction to an electrochemical one directly and harvest the electrical energy instead of the thermal energy? For example in my chemistry textbook it says:

$$\ce{CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(g) + energy}$$

The book then says: "Even though none of the reactants or products in this reaction is ionic, the reaction is still assumed to involve a transfer of electrons from carbon to oxygen"

my question is, why is it necessary for us to burn fuel in say combustion engines if technically electrons are being transferred, is it possible to create a new engine that will take say one of the hydrocarbons found in gasoline plus oxygen and instead somehow turn the generated energy to the electrical form directly without burning it? Perhaps some complicated engine that uses a cycle similar to the ATP cycle

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    $\begingroup$ It's not that easy to do that, but it is in principle how a fuel cell works. $\endgroup$ – Zhe Jan 10 '19 at 19:31
  • $\begingroup$ I'll say that any reaction which is spontaneous and violent can be transformed into one that is controlled and electrochemical. Only in some cases you have to take more detours than in others, and depending on the specifics, you still lose some energy into heat. $\endgroup$ – Karl Jan 10 '19 at 20:13
  • $\begingroup$ As @Zhe states, there are methane fuel cells: futurity.org/fuel-cell-methane-1910432 . At room temperature, though, methanol is easier to use. $\endgroup$ – DrMoishe Pippik Jan 10 '19 at 22:52
  • $\begingroup$ Expanding the previous comments: yes, you need a fuel cell to convert the "chemical" energy to electricity. The basic concept is so old (since 19th century) that even Wikipedia has more or less decent articles on that. Theoretical efficiency of fuel cells surpasses that of combustion engines. Why are we still not surrounded by fuel cells? Let's take the SOFC prototype from @DrMoishePippik 's comment as an example. The materials are expensive (cobalt, rare-earths), working temperatures are still high, long-term stability not well-understood, etc. Meanwhile, it is cheaper just to burn fuel. $\endgroup$ – voffch Jan 13 '19 at 19:03
  • $\begingroup$ Thanks everyone, I didn't know anything about fuel cells before seeing the comments. $\endgroup$ – Sasha1296 Jan 19 '19 at 4:44

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