Value‐Added Formate Production from Selective Methanol Oxidation as Anodic Reaction to Enhance Electrochemical Hydrogen Cogeneration

Abstract

Electrolytic overall water splitting is a promising approach to produce H2, but its efficiency is severely limited by the sluggish kinetics of the oxygen evolution reaction (OER) and the low activity of current electrocatalysts. To solve these problems, in addition to the development of efficient precious‐metal catalysts, an effective strategy is proposed to replace the OER by the selective methanol oxidation reaction. Ni–Co hydroxide [NixCo1−x(OH)2] nanoarrays were obtained through a facile hydrothermal treatment as the bifunctional electrocatalysts for the co‐electrolysis of methanol/water to produce H2 and value‐added formate simultaneously. The electrocatalyst could catalyze selective methanol oxidation (≈1.32 V) with a significantly lower energy consumption (≈0.2 V less) than OER. Importantly, methanol was transformed exclusively to value‐added formate with a high Faradaic efficiency (selectivity) close to 100 %. Specifically, a cell voltage of only approximately 1.5 V was required to generate a current density of 10 mA cm−2. Furthermore, the Ni0.33Co0.67(OH)2/Ni foam nanoneedle arrays presented an outstanding stability for overall co‐electrolysis.

Co P@NiCo-LDH heteronanosheet arrays as efficient bifunctional electrocatalysts for co-generation of value-added formate and hydrogen with less-energy consumption

“…The efficiency of charge transfer depends on the surface charge density of electrocatalysts, which governs the activity and selectivity [12 , 14 , 43 , 45 , 50] . Therefore, motivated by the selective electrooxidation of other alcohols [25][26][27][28][29][30][31] , continuous electrolysis is performed at a constant potential of 1.35 V vs. RHE in order to trace the anodic products. As shown in Fig.…”

“…Recently, an efficient strategy has been developed to replace OER by thermodynamic favorable anodic oxidation reaction in water since it can be integrated with HER to generate H 2 with less electrical energy consumption [6-8 , 13] . To realize the coelectrolysis, some reduced agents and organics substrate molecules have been used to optimizing the aqueous electrolyte, such as: urea [18 , 19] , hydrazine [20 , 21] , ammonia [22][23][24] , alcohols [25][26][27][28][29][30][31] , furfural [7 , 13 , 32 , 33] , biomass-derived intermediate compounds [34 , 35] , etc. Comparing to the traditional water electrolysis with HER and OER, these co-electrolysis reactions could significantly decrease operating voltage to produce hydrogen.…”

Nickel Iron Diselenide for Highly Efficient and Selective Electrocatalytic Conversion of Methanol to Formate

“…[ 5 ] This is a cost‐effective process because the price per metric ton of formate is fourfold higher than that of methanol. [ 6,7 ] Formate is an essential and highly versatile chemical in many sectors, including chemical, textile, rubber, leather, pharmaceutic, and printing industries. Formic acid can be also used as a fuel in direct formic acid fuel cells and for hydrogen storage.…”

Selective Methanol‐to‐Formate Electrocatalytic Conversion on Branched Nickel Carbide

“…Currently, close to one million tons of formic acid are yearly produced from the combination of methanol with CO at 40 atm and 80 °C and the hydrolysis of the resulting methyl formate [7] . Owing to the high energy used in this process and the high demand, the price per metric ton of formate is a fourfold higher than that of methanol [8, 9] . Therefore, the selective oxidation of methanol to formate can be economically profitable if a proper strategy to collect the reaction product was developed.…”

“…[7] Owing to the high energy used in this process and the high demand, the price per metric ton of formate is a fourfold higher than that of methanol. [8,9] Therefore, the selective oxidation of methanol to formate can be economically profitable if a proper strategy to collect the reaction product was developed.…”