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The thermochemical conversion of different feedstocks is a technology capable of reducing the amount of biowaste materials produced. In addition, the gasification of feedstock using steam as a gasifying agent also produces hydrogen, which is a clean energy fuel. This article aimed to encapsulate the current status of biowaste gasification and to explain, in detail, the advantages and limitations of gasification technologies. In this review paper, different gasifying agents such as steam, air, and oxygen, as well as their effects on the quality of syngas production, are discussed. In addition, the effects of reactor configuration and different operating parameters, such as temperature, pressure, equivalence ratio, and incorporation of a catalyst, as well as their effects on the ratio of H2/CO, LHV, syngas yield, and tar production, were critically evaluated. Although gasification is a sustainable and ecologically sound biomass utilization technology, tar formation is the main problem in the biomass gasification process. Tar can condense in the reactor, and clog and contaminate equipment. It has been shown that an optimized gasifier and a high-activity catalyst can effectively reduce tar formation. However, key biowaste treatment technologies and concepts must first be improved and demonstrated at the market level to increase stakeholder confidence. Gasification can be the driving force of this integration, effectively replacing fossil fuels with produced gas. In addition, support policies are usually needed to make the integration of biomass gasification technology into the industry profitable with fully functional gasification plants. Therefore, to address such issues, this study focused on addressing these issues and an overview of gasification concepts.

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The conversion and storage technologies of sustainable energy have been thoroughly researched, considering the overconsumption of fossil fuels and the escalating environmental problems. The use of more environmentally benign energy vectors has helped fuel cells recently become one of the most promising technologies. These devices' oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are vital processes, but their commercialization is severely constrained by slow kinetics. Consequently, creating highly effective ORR and OER bifunctional catalysts is crucial yet difficult. Pt-based catalysts have the best ORR activity but weak OER activity. The best commercial OER electrocatalysts are RuO2 and IrO2 based, although they have a subpar ORR characteristic. However, it is crucial to create electrocatalysts with low noble metal contents and high efficiencies and stabilities for OER and ORR applications. At the same time, the large-scale applications of these noble electrocatalysts are constrained due to their rarity, high cost, and poor stability. In this review paper, noble metal-based and free catalysts for ORR and OER have been reviewed.

The direct methanol fuel cell (DMFC) is a fuel cell technology capable of generating energy through the electrochemical oxidation of methanol. The methanol oxidation reaction (MOR), which occurs at the anode, is of interest for producing renewable energy. This process relies on precious metal catalysts to efficiently produce energy, namely nanoscale Pt-Ru. Current fuel cell technology is, therefore, expensive, and unsuitable for large-scale implementation. Palladium can act as an electrocatalyst for the process, similar to platinum. However, its monometallic form suffers from high overpotentials and significant poisoning by carbon monoxide (CO) generated in situ. Previous research has shown improved activity of palladium in alkaline electrolytes, which, while unsuitable for platinum, are known to enhance alcohol oxidation reaction kinetics through preferred oxidation of methanol. The addition of a secondary metal assists in both modulations of palladium-reactant binding strengths and co-catalyzed oxidation of CO when exposed to the surface. This article reviews the literature on DMFC and anode electrocatalysts. The current platinum catalysts and foundation knowledge of the mechanism of platinum are compared to current palladium catalysts. The requirements for new nanoscale palladium catalysts and background on their synthesis are outlined.