Introduction
Renewable and clean energy sources have been sought to be a substitute for fossil fuels that pose environmentally negative impacts such as the pollutant emission of carbon dioxide, carbon monoxide, hydrocarbon, nitrogen oxide and ashes.
Hydrogen is extensively known as an ideal clean energy
source due to its high specific energy content (122 kJ g 1) [1,2] and zero carbon emission after its combustion [3]. Hydrogen can be generated from various strategies by thermochemical, electrochemical, and biological processes [4]. Biological hydrogen production is less energy intensive than non- biological processes, and so is considered more environmentally friendly. Hydrogen is generated as a product of several