Ni nanoparticles embedded in MoO2 micropillars as a heterojunction electrocatalyst for electrolysis of potassium carbonate solution to generate hydrogen and KOH

Direct air carbon dioxide capture (DAC) is one of the promising ways to alleviate the increased carbon dioxide concentration in the atmosphere. Inorganic alkaline (KOH, NaOH, etc.) solutions, with strong alkalinity and low cost, are regarded as efficient absorbents for low-concentration CO 2 in air. To efficiently regenerate KOH from the K 2 CO 3 /KHCO 3 solution, the ion-selective membrane electrolysis method has attracted concern in recent years, which generates both high-concentration KOH solution and H 2 simultaneously. In order to reduce the cell voltage of the K 2 CO 3 /KHCO 3 electrolysis, the present paper proposes a two-step process of hydrothermal treatment and annealing to fabricate a heterojunction electrocatalyst with Ni nanoparticles in situ anchored on MoO 2 micropillars. In the prepared Ni NPs/MoO 2 MPs heterojunction catalyst, MoO 2 promotes the dissociation of the adsorbed water molecules and optimizes the H adsorption on the adjacent Ni active site. As a result, the Ni NPs/MoO 2 MPs catalyst shows an extremely low overpotential of 13 mV at 10 mA cm −2 in 1 M KOH and negligible performance deterioration after 100 h of electrolysis at 300 mA cm −2 , and 1000 CV cycles. Moreover, the electrolysis cell with Ni NPs/MoO 2 MPs cathode for electrolysis of carbonate solution achieves a high cathode current efficiency (>97 %) to generate high concentration KOH (6.9 M) solution, and a cell voltage of 2.69 V at 200 mA cm −2 , showing a superior performance to that of the precious Pt/C electrode-based cell. This non-precious Ni NPs/MoO 2 MPs electrocatalyst shows promising prospects for highly efficient electrolysis of K 2 CO 3 to generate H 2 and KOH.