Scientists from Hong Kong Polytechnic claim to have demonstrated a graphene-based battery that harvests ambient energy and turns it into electricity.
The claim, however, has been questioned by another member of the university.
In their paper, published on Arxiv here, the researchers say they were able to get around 0.35V for 25 days by arranging silver and gold electrodes on a graphene sheet, and immersing it in a copper chloride solution.
In their paper, the team, led by Zihan Xu of the university’s Department of Applied Physics and Materials Research, says the voltage they observed didn’t come from a chemical reaction within the solution, but rather from kinetic energy of ions in the solution.
The problem with trying to turn ambient energy into something useful is that it’s random: a collision might release an electron, but there’s no way to predict which way it will flow in a circuit. The Hong Kong researchers claim that they by using different metals at each end of the graphene – gold at one end, silver at the other – they observed a voltage flowing in one direction.
In support of the idea that the voltage is harvested from ambient energy, the researchers write that voltage changed if the copper chloride was heated, or if it was excited by ultrasound.
According to Physorg, however, the experiment so far fails the reproducibility test, with one of the researchers’ graduate supervisors, Dr Wanlin Guo, saying he had not been able to reproduce the results independently. ®