A review of recent advances in alkaline electrolyzer for green hydrogen production: Performance improvement and applications

As climate change accelerates, finding clean alternatives to fossil fuels is more urgent than ever. Therefore, green hydrogen has been introduced as a means of high-intensity energy storage medium for surplus renewable electricity and could be a critical enabler of the global transition to sustainable and net zero emissions energy future. Considering this, the proposed study discusses the recent contributions in the state-of-the-art alkaline electrolyzer which is known as a low-cost and robust structure hydrogen production device. The work thoroughly reviews the recent performance improvement methods and the applications. The performance improvement methods are divided into parametric optimization and overpotential reduction via innovative electrode materials, its fabrication methods, and novel separator materials. Accordingly, an enhanced electrode made of Ni-wire mesh could reach a current density of 2 A/cm2 at a cell voltage of 1.85 V which is comparable to that of high-cost proton exchange membrane electrolyzer. The applications of alkaline electrolyzer are classified into standalone large-scale hydrogen production systems and the additional system as means of a hybrid system for energy recovery applications. A hydrogen production capacity of 1,374,142 kg/year was obtained by adopting wind energy during the off-grid hours. Furthermore, a comprehensive bibliometric analysis was conducted using VOSviewer program in order to illustrate the trend in hydrogen production in terms of indexed keywords, authors' keywords, country citation, authors' collaborative, and journals' bibliographic coupling.