With the increasingly serious energy crisis and environmental pollution, hydrogen energy is considered as one of the most attractive energy due to its high energy density, non-polluting combustion products, and easy availability [1], [2], [3], [4]. Among the numerous methods of hydrogen production, water electrolysis for producing hydrogen has been a research hotspot [5], [6]. The electrolysis of water consists of two half-reactions, the hydrogen evolution reaction (HER) [7] and the oxygen evolution reaction (ORE). The OER requires a high overpotential (1.23 V vs HRE), which hinders the development and application of hydrogen evolution from water [8].

To reduce the anodic oxidation potential of water, it is important to improve the catalytic activities of electrocatalysts by using effective methods such as redox reactions, surface reconstruction, and component leaching [9]. For example, L. Gao, et al. shows that the transition metal oxide of the catalyst is excited by photothermal effect to undergo surface recombination and partial leaching, and is dynamically transformed into active hydroxide, thus realizing efficient oxygen release [10]. In addition, the oxidation reaction of small molecule organics to replace OER has become a promising strategy to reduce the reaction potential of OER [11]. Common organic compounds used in oxidation reactions include alcohols (methanol or ethanol) [12], [13], [14], [15], [16], urea [17], [18], [19], amines [20], furfural [21], [22], and 5-hydroxymethyl furfural [23], [24], [25], [26]. Compared with the OER, the reaction substrates based on these small organic molecules have better kinetic performance in the oxidation reaction, thereby reducing the anode potential [27]. In addition, the use of the oxidation reaction of small molecular organics instead of the OER reaction shows other advantages, such as reducing the risk of explosion caused by the mixing of O2 and H2 produced during water electrolysis. Among the numerous reaction substrates, methanol has attracted great attention because it is the simplest structural alcohol and can be synthesized in large quantities by biological or chemical industries. On the one hand, methanol oxidation reaction (MOR) has fast kinetics due to the good solubility of methanol, and oxidation reactions can occur at lower potentials so that MOR can compete with OER and react preferentially. On the other hand, among the products of methanol selective oxidation, formic acid or formate has a certain economic value, so selective MOR becomes an ideal substitution reaction for OER. Many studies have shown that Pt has excellent electrocatalytic performance for complete MOR [24], [28], [29], but it still needs to face some problems such as 1) the high cost of Pt; 2) easy deactivation by CO adsorption during the reaction; 3) complete oxidation of methanol to produce greenhouse pollutant CO2 [29]. Great efforts have been made to improve the catalytic activity of Pt catalysts, and a recent study reported by P. Deng, et al. has demonstrated the application of a simple solvothermal method to synthesize ternary Pt3Bi3Zn NPLs electrocatalysts, which are applied in MOR processes for their mass, the activity can reach 3.29 A mg-1Pt [30]. In addition, L. Yan, et al. synthesized Pt/Ni(OH)2/nitrogen-doped graphene catalysts on Ni(OH)2 nanosheets using Pt as a carrier. The catalyst is designed with a multi-dimensional porous structure and abundant hydroxyl compounds, which can promote the oxidation of intermediate CO. When promoting the MOR, the catalyst also reduces the possibility of CO adsorption poisoning. The mass activity of the catalyst in MOR catalysis is 2.99 A mg-1Pt [31]. Although great efforts have been made to improve MOR catalytic performance and reduce Pt loading, the further improvement in product selectivity and reduced Pt loading is still worth noting. Recent studies have shown that adjusting the surface energy of catalysts by introducing defects can effectively solve the problem of Pt poisoned by CO adsorption in the MOR, thereby improving the stability of Pt in the MOR [28]. H. Xu, et al. prepared a novel ae-PtTeCo NRs electrocatalyst with surface defects and controlled electronic structure induced by alkali etching, which exhibited excellent activity for MOR with a mass activity of 1.47 A mg-1Pt. In addition, due to its abundant surface defects and unique electronic structure, the adsorption of CO during the catalytic MOR is greatly reduced, and the stability is greatly improved [32]. Therefore, this study reveals the significance of surface defects for metal atomic modification and surface reconstruction. The research of K. Xiang, et al. showed that the introduction of Pt atoms by oxygen vacancies could effectively reduce the reaction potential of MOR [28]. As a kind of defect, vacancy also plays an important role in improving CO poisoning of Pt in the MOR. Phosphorus vacancy can generate a new electronic state and novel electronic state and active structure, which can effectively improve electrical conductivity and surface activity [33], [34], [35], [36]. Therefore, phosphorus vacancies are an effective way to tune the promoted phosphide electrocatalysts.

Herein, it is the first time to propose a design idea for the development of MOR electrocatalysts by introducing noble metal elements through phosphorus vacancies. Phosphorus vacancies are used as important surface defect regulation means, and a very small amount of Pt clusters is introduced as MOR reactive sites. The loading of Pt is only 12.97 μg cm−2, and the synergistic effect with the substrate material Ni2P enables efficient MOR at a low potential (0.6 V vs RHE), and the mass activity of Pt can reach 9.16 A mg-1Pt. The unique defect structure and electronic structure of phosphorus vacancies can also effectively reduce the adsorption of Pt for MOR intermediate CO. The catalyst can generate H2 from HER and formate from MOR. Moreover, the Faraday efficiency of these products is close to 100%. At the same time, no CO2 is generated during the procedure, which ensures environmental friendliness and improves the overall value of the reaction.