RESUMEN
Titanium (Ti) is widely used as anode current collectors in proton exchange membrane (PEM)-based water electrolyzers due to its self-passivated oxide layer, which protects it from corrosion in acidic solutions. However, the cost of the material and machining process for Ti is high. A wider utilization of water electrolyzers to produce hydrogen could be favored by the use of less expensive coated aluminum (Al) substrates, which could potentially replace high-cost Ti-based components. It is shown here by depositing a pinhole-free oxygen vacancy-rich titanium oxide (TiOx) protection layer by atomic layer deposition (ALD), the corrosion resistance of Al substrates in acidic environments at oxygen evolution potentials can be enhanced. The optimization of the oxygen vacancy concentration is accomplished by tuning the ALD parameters to achieve ideal stoichiometry and conformal coating on rough substrates. The robustness of the coatings was evaluated at high potentials (2.4 V vs NHE = normal hydrogen electrode) in low pH conditions. A low TiOx dissolution rate of the order of â¼6 nm year-1 was observed. By testing under industrially relevant conditions, i.e., high applied voltages (2.4 V) and low pH, an Al loss at around the zero ppb level was achieved using optimized ALD parameters. It is proposed that a 40 nm TiOx coating on Al may be adequate to provide 60,000 h of durability in a PEM water electrolyzer anode current collector.
RESUMEN
BACKGROUND: Inadequate access to quality health care services due to weak health systems and recurrent public health emergencies are impediments to the attainment of Universal Health Coverage and health security in Africa. To discuss these challenges and deliberate on plausible solutions, the World Health Organization Regional Office for Africa, in collaboration with the Government of Cabo Verde, convened the second Africa Health Forum in Praia, Cabo Verde on 26-28 March 2019, under the theme Achieving Universal Health Coverage and Health Security: The Africa We Want to See. METHODS: The Forum was conducted through technical sessions consisting of high-level, moderated panel discussions on specific themes, some of them preceded by keynote addresses. There were booth exhibitions by Member States, World Health Organization and other organizations to facilitate information exchanges. A Communiqué highlighting the recommendations of the Forum was issued during the closing ceremony . More than 750 participants attended. Relevant information from the report of the Forum and notes by the authors were extracted and synthesized into these proceedings. CONCLUSIONS: The Forum participants agreed that the role of community engagement and participation in the attainment of Universal Health Coverage, health security and ultimately the Sustainable Development Goals cannot be overemphasized. The public sector of Africa alone cannot achieve these three interrelated goals; other partners, such as the private sector, must be engaged. Technological innovations will be a key driver of the attainment of these goals; hence, there is need to harness the comparative advantages that they offer. Attainment of the three goals is also intertwined - achieving one paves the way for achieving the others. Thus, there is need for integrated public health approaches in the planning and implementation of interventions aimed at achieving them. RECOMMENDATIONS: To ensure that the recommendations of this Forum are translated into concrete actions in a sustainable manner, we call on African Ministers of Health to ensure their integration into national health sector policies and strategic documents and to provide the necessary leadership required for their implementation. We also call on partners to mainstream these recommendations into their ongoing support to World Health Organization African Member States.