物理学：電気化学を用いた核融合反応速度の促進

An electrochemical method for enhancing deuterium fusion rates is described in Nature. Although this scheme is still a long way from being able to produce more energy than is consumed, the experiment demonstrates the possibility of using low-energy electrochemical processes to influence nuclear reaction rates at much higher energy scales.

Nuclear fusion, the process that powers the Sun, involves the combining of two light atomic nuclei into a single heavier nucleus, which releases energy. Fusion is thought to have potential as a clean energy source, but current fusion reactors cannot produce enough fusion events to generate more power than they consume. One factor controlling fusion rates is the density of the fuel — higher densities increase the probability of particle collisions, and hence the probability that they will undergo fusion.

In one approach to fusion power, a combination of magnetic fields, temperatures and pressures is used to compress the nuclear fuel (typically a plasma of deuterium, a heavy isotope of hydrogen) to the point where fusion occurs. However, this is still a work in progress.

Curtis Berlinguette and colleagues explore a different route for boosting the fusion rate of deuterium — one that uses electrochemistry. They designed a benchtop particle accelerator, named the Thunderbird Reactor, that bombards a palladium target with a beam of deuterium ions: as the deuterium concentration implanted in the palladium rises, so does the rate of fusion events resulting from collisions between the implanted deuterium and those newly arriving in the beam, until a steady state is reached. The palladium target is also attached to an electrochemical cell and, when this is turned on, additional deuterium is loaded into the target, and the fusion rate increases. On average, the fusion rate increased by 15% compared with no electrochemical loading. The authors note that in its present incarnation, the Thunderbird Reactor only produces approximately 1x10^-9 (one billionth) W of power for every 15 W of input power.

Energy-efficient nuclear fusion remains a challenge for now. “Nevertheless, the use of electrochemistry to increase the rate of nuclear fusion is a considerable achievement,” Amy McKeown-Green and Jennifer Dionne write in an accompanying News & Views. “Equipped with technological developments that span nuclear physics, chemistry and materials science, the authors are paving the way for a more widespread investigation of low-energy fusion driven by accessible, bench-top nuclear reactors,” they add.